BuildBot Manual 0.7.5

Table of Contents

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This is the BuildBot manual.

Copyright (C) 2005,2006 Brian Warner

Copying and distribution of this file, with or without modification, are permitted in any medium without royalty provided the copyright notice and this notice are preserved.

--- The Detailed Node Listing ---


System Architecture


Creating a buildslave



Version Control Systems



Listing Change Sources and Schedulers

Getting Source Code Changes

Change Sources

Build Process

Build Steps

Source Checkout

Simple ShellCommand Subclasses

Python BuildSteps

Writing New BuildSteps

Build Factories

BuildStep Objects


Process-Specific build factories

Status Delivery

Command-line tool

Developer Tools

Other Tools

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1 Introduction

The BuildBot is a system to automate the compile/test cycle required by most software projects to validate code changes. By automatically rebuilding and testing the tree each time something has changed, build problems are pinpointed quickly, before other developers are inconvenienced by the failure. The guilty developer can be identified and harassed without human intervention. By running the builds on a variety of platforms, developers who do not have the facilities to test their changes everywhere before checkin will at least know shortly afterwards whether they have broken the build or not. Warning counts, lint checks, image size, compile time, and other build parameters can be tracked over time, are more visible, and are therefore easier to improve.

The overall goal is to reduce tree breakage and provide a platform to run tests or code-quality checks that are too annoying or pedantic for any human to waste their time with. Developers get immediate (and potentially public) feedback about their changes, encouraging them to be more careful about testing before checkin.


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1.1 History and Philosophy

The Buildbot was inspired by a similar project built for a development team writing a cross-platform embedded system. The various components of the project were supposed to compile and run on several flavors of unix (linux, solaris, BSD), but individual developers had their own preferences and tended to stick to a single platform. From time to time, incompatibilities would sneak in (some unix platforms want to use string.h, some prefer strings.h), and then the tree would compile for some developers but not others. The buildbot was written to automate the human process of walking into the office, updating a tree, compiling (and discovering the breakage), finding the developer at fault, and complaining to them about the problem they had introduced. With multiple platforms it was difficult for developers to do the right thing (compile their potential change on all platforms); the buildbot offered a way to help.

Another problem was when programmers would change the behavior of a library without warning its users, or change internal aspects that other code was (unfortunately) depending upon. Adding unit tests to the codebase helps here: if an application's unit tests pass despite changes in the libraries it uses, you can have more confidence that the library changes haven't broken anything. Many developers complained that the unit tests were inconvenient or took too long to run: having the buildbot run them reduces the developer's workload to a minimum.

In general, having more visibility into the project is always good, and automation makes it easier for developers to do the right thing. When everyone can see the status of the project, developers are encouraged to keep the tree in good working order. Unit tests that aren't run on a regular basis tend to suffer from bitrot just like code does: exercising them on a regular basis helps to keep them functioning and useful.

The current version of the Buildbot is additionally targeted at distributed free-software projects, where resources and platforms are only available when provided by interested volunteers. The buildslaves are designed to require an absolute minimum of configuration, reducing the effort a potential volunteer needs to expend to be able to contribute a new test environment to the project. The goal is for anyone who wishes that a given project would run on their favorite platform should be able to offer that project a buildslave, running on that platform, where they can verify that their portability code works, and keeps working.

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1.2 System Architecture

The Buildbot consists of a single buildmaster and one or more buildslaves, connected in a star topology. The buildmaster makes all decisions about what, when, and how to build. It sends commands to be run on the build slaves, which simply execute the commands and return the results. (certain steps involve more local decision making, where the overhead of sending a lot of commands back and forth would be inappropriate, but in general the buildmaster is responsible for everything).

The buildmaster is usually fed Changes by some sort of version control system (see Change Sources), which may cause builds to be run. As the builds are performed, various status messages are produced, which are then sent to any registered Status Targets (see Status Delivery).

Overview Diagram

The buildmaster is configured and maintained by the “buildmaster admin”, who is generally the project team member responsible for build process issues. Each buildslave is maintained by a “buildslave admin”, who do not need to be quite as involved. Generally slaves are run by anyone who has an interest in seeing the project work well on their favorite platform.

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1.2.1 BuildSlave Connections

The buildslaves are typically run on a variety of separate machines, at least one per platform of interest. These machines connect to the buildmaster over a TCP connection to a publically-visible port. As a result, the buildslaves can live behind a NAT box or similar firewalls, as long as they can get to buildmaster. The TCP connections are initiated by the buildslave and accepted by the buildmaster, but commands and results travel both ways within this connection. The buildmaster is always in charge, so all commands travel exclusively from the buildmaster to the buildslave.

To perform builds, the buildslaves must typically obtain source code from a CVS/SVN/etc repository. Therefore they must also be able to reach the repository. The buildmaster provides instructions for performing builds, but does not provide the source code itself.

BuildSlave Connections

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1.2.2 Buildmaster Architecture

The Buildmaster consists of several pieces:

BuildMaster Architecture

Each Builder is configured with a list of BuildSlaves that it will use for its builds. These buildslaves are expected to behave identically: the only reason to use multiple BuildSlaves for a single Builder is to provide a measure of load-balancing.

Within a single BuildSlave, each Builder creates its own SlaveBuilder instance. These SlaveBuilders operate independently from each other. Each gets its own base directory to work in. It is quite common to have many Builders sharing the same buildslave. For example, there might be two buildslaves: one for i386, and a second for PowerPC. There may then be a pair of Builders that do a full compile/test run, one for each architecture, and a lone Builder that creates snapshot source tarballs if the full builders complete successfully. The full builders would each run on a single buildslave, whereas the tarball creation step might run on either buildslave (since the platform doesn't matter when creating source tarballs). In this case, the mapping would look like:

     Builder(full-i386)  ->  BuildSlaves(slave-i386)
     Builder(full-ppc)   ->  BuildSlaves(slave-ppc)
     Builder(source-tarball) -> BuildSlaves(slave-i386, slave-ppc)

and each BuildSlave would have two SlaveBuilders inside it, one for a full builder, and a second for the source-tarball builder.

Once a SlaveBuilder is available, the Builder pulls one or more BuildRequests off its incoming queue. (It may pull more than one if it determines that it can merge the requests together; for example, there may be multiple requests to build the current HEAD revision). These requests are merged into a single Build instance, which includes the SourceStamp that describes what exact version of the source code should be used for the build. The Build is then assigned to a SlaveBuilder and the build begins.

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1.2.3 Status Delivery Architecture

The buildmaster maintains a central Status object, to which various status plugins are connected. Through this Status object, a full hierarchy of build status objects can be obtained.

Status Delivery

The configuration file controls which status plugins are active. Each status plugin gets a reference to the top-level Status object. From there they can request information on each Builder, Build, Step, and LogFile. This query-on-demand interface is used by the html.Waterfall plugin to create the main status page each time a web browser hits the main URL.

The status plugins can also subscribe to hear about new Builds as they occur: this is used by the MailNotifier to create new email messages for each recently-completed Build.

The Status object records the status of old builds on disk in the buildmaster's base directory. This allows it to return information about historical builds.

There are also status objects that correspond to Schedulers and BuildSlaves. These allow status plugins to report information about upcoming builds, and the online/offline status of each buildslave.

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1.3 Control Flow

A day in the life of the buildbot:

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2 Installation

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2.1 Requirements

At a bare minimum, you'll need the following (for both the buildmaster and a buildslave):

Certain other packages may be useful on the system running the buildmaster:

And of course, your project's build process will impose additional requirements on the buildslaves. These hosts must have all the tools necessary to compile and test your project's source code.

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2.2 Installing the code

The Buildbot is installed using the standard python distutils module. After unpacking the tarball, the process is:

     python build
     python install

where the install step may need to be done as root. This will put the bulk of the code in somewhere like /usr/lib/python2.3/site-packages/buildbot . It will also install the buildbot command-line tool in /usr/bin/buildbot.

To test this, shift to a different directory (like /tmp), and run:

     buildbot --version

If it shows you the versions of Buildbot and Twisted, the install went ok. If it says no such command or it gets an ImportError when it tries to load the libaries, then something went wrong. pydoc buildbot is another useful diagnostic tool.

Windows users will find these files in other places. You will need to make sure that python can find the libraries, and will probably find it convenient to have buildbot on your PATH.

If you wish, you can run the buildbot unit test suite like this:

     PYTHONPATH=. trial buildbot.test

This should run up to 192 tests, depending upon what VC tools you have installed. On my desktop machine it takes about five minutes to complete. Nothing should fail, a few might be skipped. If any of the tests fail, you should stop and investigate the cause before continuing the installation process, as it will probably be easier to track down the bug early.

If you cannot or do not wish to install the buildbot into a site-wide location like /usr or /usr/local, you can also install it into the account's home directory. Do the install command like this:

     python install --home=~

That will populate ~/lib/python and create ~/bin/buildbot. Make sure this lib directory is on your PYTHONPATH.

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2.3 Creating a buildmaster

As you learned earlier (see System Architecture), the buildmaster runs on a central host (usually one that is publically visible, so everybody can check on the status of the project), and controls all aspects of the buildbot system. Let us call this host

You may wish to create a separate user account for the buildmaster, perhaps named buildmaster. This can help keep your personal configuration distinct from that of the buildmaster and is useful if you have to use a mail-based notification system (see Change Sources). However, the Buildbot will work just fine with your regular user account.

You need to choose a directory for the buildmaster, called the basedir. This directory will be owned by the buildmaster, which will use configuration files therein, and create status files as it runs. ~/Buildbot is a likely value. If you run multiple buildmasters in the same account, or if you run both masters and slaves, you may want a more distinctive name like ~/Buildbot/master/gnomovision or ~/Buildmasters/fooproject. If you are using a separate user account, this might just be ~buildmaster/masters/fooproject.

Once you've picked a directory, use the buildbot create-master command to create the directory and populate it with startup files:

     buildbot create-master basedir

You will need to create a configuration file (see Configuration) before starting the buildmaster. Most of the rest of this manual is dedicated to explaining how to do this. A sample configuration file is placed in the working directory, named master.cfg.sample, which can be copied to master.cfg and edited to suit your purposes.

(Internal details: This command creates a file named buildbot.tac that contains all the state necessary to create the buildmaster. Twisted has a tool called twistd which can use this .tac file to create and launch a buildmaster instance. twistd takes care of logging and daemonization (running the program in the background). /usr/bin/buildbot is a front end which runs twistd for you.)

In addition to buildbot.tac, a small Makefile.sample is installed. This can be used as the basis for customized daemon startup, See Launching the daemons.

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2.4 Creating a buildslave

Typically, you will be adding a buildslave to an existing buildmaster, to provide additional architecture coverage. The buildbot administrator will give you several pieces of information necessary to connect to the buildmaster. You should also be somewhat familiar with the project being tested, so you can troubleshoot build problems locally.

The buildbot exists to make sure that the project's stated “how to build it” process actually works. To this end, the buildslave should run in an environment just like that of your regular developers. Typically the project build process is documented somewhere (README, INSTALL, etc), in a document that should mention all library dependencies and contain a basic set of build instructions. This document will be useful as you configure the host and account in which the buildslave runs.

Here's a good checklist for setting up a buildslave:

  1. Set up the account

    It is recommended (although not mandatory) to set up a separate user account for the buildslave. This account is frequently named buildbot or buildslave. This serves to isolate your personal working environment from that of the slave's, and helps to minimize the security threat posed by letting possibly-unknown contributors run arbitrary code on your system. The account should have a minimum of fancy init scripts.

  2. Install the buildbot code

    Follow the instructions given earlier (see Installing the code). If you use a separate buildslave account, and you didn't install the buildbot code to a shared location, then you will need to install it with --home=~ for each account that needs it.

  3. Set up the host

    Make sure the host can actually reach the buildmaster. Usually the buildmaster is running a status webserver on the same machine, so simply point your web browser at it and see if you can get there. Install whatever additional packages or libraries the project's INSTALL document advises. (or not: if your buildslave is supposed to make sure that building without optional libraries still works, then don't install those libraries).

    Again, these libraries don't necessarily have to be installed to a site-wide shared location, but they must be available to your build process. Accomplishing this is usually very specific to the build process, so installing them to /usr or /usr/local is usually the best approach.

  4. Test the build process

    Follow the instructions in the INSTALL document, in the buildslave's account. Perform a full CVS (or whatever) checkout, configure, make, run tests, etc. Confirm that the build works without manual fussing. If it doesn't work when you do it by hand, it will be unlikely to work when the buildbot attempts to do it in an automated fashion.

  5. Choose a base directory

    This should be somewhere in the buildslave's account, typically named after the project which is being tested. The buildslave will not touch any file outside of this directory. Something like ~/Buildbot or ~/Buildslaves/fooproject is appropriate.

  6. Get the buildmaster host/port, botname, and password

    When the buildbot admin configures the buildmaster to accept and use your buildslave, they will provide you with the following pieces of information:

  7. Create the buildslave

    Now run the 'buildbot' command as follows:

              buildbot create-slave BASEDIR MASTERHOST:PORT SLAVENAME PASSWORD

    This will create the base directory and a collection of files inside, including the buildbot.tac file that contains all the information you passed to the buildbot command.

  8. Fill in the hostinfo files

    When it first connects, the buildslave will send a few files up to the buildmaster which describe the host that it is running on. These files are presented on the web status display so that developers have more information to reproduce any test failures that are witnessed by the buildbot. There are sample files in the info subdirectory of the buildbot's base directory. You should edit these to correctly describe you and your host.

    BASEDIR/info/admin should contain your name and email address. This is the “buildslave admin address”, and will be visible from the build status page (so you may wish to munge it a bit if address-harvesting spambots are a concern).

    BASEDIR/info/host should be filled with a brief description of the host: OS, version, memory size, CPU speed, versions of relevant libraries installed, and finally the version of the buildbot code which is running the buildslave.

    If you run many buildslaves, you may want to create a single ~buildslave/info file and share it among all the buildslaves with symlinks.

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2.4.1 Buildslave Options

There are a handful of options you might want to use when creating the buildslave with the buildbot create-slave <options> DIR <params> command. You can type buildbot create-slave --help for a summary. To use these, just include them on the buildbot create-slave command line, like this:

     buildbot create-slave --umask=022 ~/buildslave myslavename mypasswd
This is a boolean flag that tells the buildslave whether to launch child processes in a PTY (the default) or with regular pipes. The advantage of using a PTY is that “grandchild” processes are more likely to be cleaned up if the build is interrupted or times out (since it enables the use of a “process group” in which all child processes will be placed). The disadvantages: some forms of Unix have problems with PTYs, some of your unit tests may behave differently when run under a PTY (generally those which check to see if they are being run interactively), and PTYs will merge the stdout and stderr streams into a single output stream (which means the red-vs-black coloring in the logfiles will be lost). If you encounter problems, you can add --usepty=0 to disable the use of PTYs. Note that windows buildslaves never use PTYs.
This is a string (generally an octal representation of an integer) which will cause the buildslave process' “umask” value to be set shortly after initialization. The “twistd” daemonization utility forces the umask to 077 at startup (which means that all files created by the buildslave or its child processes will be unreadable by any user other than the buildslave account). If you want build products to be readable by other accounts, you can add --umask=022 to tell the buildslave to fix the umask after twistd clobbers it. If you want build products to be writable by other accounts too, use --umask=000, but this is likely to be a security problem.
This is a number that indicates how frequently “keepalive” messages should be sent from the buildslave to the buildmaster, expressed in seconds. The default (600) causes a message to be sent to the buildmaster at least once every 10 minutes. To set this to a lower value, use e.g. --keepalive=120.

If the buildslave is behind a NAT box or stateful firewall, these messages may help to keep the connection alive: some NAT boxes tend to forget about a connection if it has not been used in a while. When this happens, the buildmaster will think that the buildslave has disappeared, and builds will time out. Meanwhile the buildslave will not realize than anything is wrong.

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2.5 Launching the daemons

Both the buildmaster and the buildslave run as daemon programs. To launch them, pass the working directory to the buildbot command:

     buildbot start BASEDIR

This command will start the daemon and then return, so normally it will not produce any output. To verify that the programs are indeed running, look for a pair of files named twistd.log and that should be created in the working directory. contains the process ID of the newly-spawned daemon.

When the buildslave connects to the buildmaster, new directories will start appearing in its base directory. The buildmaster tells the slave to create a directory for each Builder which will be using that slave. All build operations are performed within these directories: CVS checkouts, compiles, and tests.

Once you get everything running, you will want to arrange for the buildbot daemons to be started at boot time. One way is to use cron, by putting them in a @reboot crontab entry1:

     @reboot buildbot start BASEDIR

When you run crontab to set this up, remember to do it as the buildmaster or buildslave account! If you add this to your crontab when running as your regular account (or worse yet, root), then the daemon will run as the wrong user, quite possibly as one with more authority than you intended to provide.

It is important to remember that the environment provided to cron jobs and init scripts can be quite different that your normal runtime. There may be fewer environment variables specified, and the PATH may be shorter than usual. It is a good idea to test out this method of launching the buildslave by using a cron job with a time in the near future, with the same command, and then check twistd.log to make sure the slave actually started correctly. Common problems here are for /usr/local or ~/bin to not be on your PATH, or for PYTHONPATH to not be set correctly. Sometimes HOME is messed up too.

To modify the way the daemons are started (perhaps you want to set some environment variables first, or perform some cleanup each time), you can create a file named Makefile.buildbot in the base directory. When the buildbot front-end tool is told to start the daemon, and it sees this file (and /usr/bin/make exists), it will do make -f Makefile.buildbot start instead of its usual action (which involves running twistd). When the buildmaster or buildslave is installed, a Makefile.sample is created which implements the same behavior as the the buildbot tool uses, so if you want to customize the process, just copy Makefile.sample to Makefile.buildbot and edit it as necessary.

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2.6 Logfiles

While a buildbot daemon runs, it emits text to a logfile, named twistd.log. A command like tail -f twistd.log is useful to watch the command output as it runs.

The buildmaster will announce any errors with its configuration file in the logfile, so it is a good idea to look at the log at startup time to check for any problems. Most buildmaster activities will cause lines to be added to the log.

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2.7 Shutdown

To stop a buildmaster or buildslave manually, use:

     buildbot stop BASEDIR

This simply looks for the file and kills whatever process is identified within.

At system shutdown, all processes are sent a SIGKILL. The buildmaster and buildslave will respond to this by shutting down normally.

The buildmaster will respond to a SIGHUP by re-reading its config file. The following shortcut is available:

     buildbot reconfig BASEDIR

When you update the Buildbot code to a new release, you will need to restart the buildmaster and/or buildslave before it can take advantage of the new code. You can do a buildbot stop BASEDIR and buildbot start BASEDIR in quick succession, or you can use the restart shortcut, which does both steps for you:

     buildbot restart BASEDIR

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2.8 Maintenance

It is a good idea to check the buildmaster's status page every once in a while, to see if your buildslave is still online. Eventually the buildbot will probably be enhanced to send you email (via the info/admin email address) when the slave has been offline for more than a few hours.

If you find you can no longer provide a buildslave to the project, please let the project admins know, so they can put out a call for a replacement.

The Buildbot records status and logs output continually, each time a build is performed. The status tends to be small, but the build logs can become quite large. Each build and log are recorded in a separate file, arranged hierarchically under the buildmaster's base directory. To prevent these files from growing without bound, you should periodically delete old build logs. A simple cron job to delete anything older than, say, two weeks should do the job. The only trick is to leave the buildbot.tac and other support files alone, for which find's -mindepth argument helps skip everything in the top directory. You can use something like the following:

     @weekly cd BASEDIR && find . -mindepth 2 -type f -mtime +14 -exec rm {} \;
     @weekly cd BASEDIR && find twistd.log* -mtime +14 -exec rm {} \;

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2.9 Troubleshooting

Here are a few hints on diagnosing common problems.

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2.9.1 Starting the buildslave

Cron jobs are typically run with a minimal shell (/bin/sh, not /bin/bash), and tilde expansion is not always performed in such commands. You may want to use explicit paths, because the PATH is usually quite short and doesn't include anything set by your shell's startup scripts (.profile, .bashrc, etc). If you've installed buildbot (or other python libraries) to an unusual location, you may need to add a PYTHONPATH specification (note that python will do tilde-expansion on PYTHONPATH elements by itself). Sometimes it is safer to fully-specify everything:

     @reboot PYTHONPATH=~/lib/python /usr/local/bin/buildbot start /usr/home/buildbot/basedir

Take the time to get the @reboot job set up. Otherwise, things will work fine for a while, but the first power outage or system reboot you have will stop the buildslave with nothing but the cries of sorrowful developers to remind you that it has gone away.

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2.9.2 Connecting to the buildmaster

If the buildslave cannot connect to the buildmaster, the reason should be described in the twistd.log logfile. Some common problems are an incorrect master hostname or port number, or a mistyped bot name or password. If the buildslave loses the connection to the master, it is supposed to attempt to reconnect with an exponentially-increasing backoff. Each attempt (and the time of the next attempt) will be logged. If you get impatient, just manually stop and re-start the buildslave.

When the buildmaster is restarted, all slaves will be disconnected, and will attempt to reconnect as usual. The reconnect time will depend upon how long the buildmaster is offline (i.e. how far up the exponential backoff curve the slaves have travelled). Again, buildbot stop BASEDIR; buildbot start BASEDIR will speed up the process.

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2.9.3 Forcing Builds

From the buildmaster's main status web page, you can force a build to be run on your build slave. Figure out which column is for a builder that runs on your slave, click on that builder's name, and the page that comes up will have a “Force Build” button. Fill in the form, hit the button, and a moment later you should see your slave's twistd.log filling with commands being run. Using pstree or top should also reveal the cvs/make/gcc/etc processes being run by the buildslave. Note that the same web page should also show the admin and host information files that you configured earlier.

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3 Concepts

This chapter defines some of the basic concepts that the Buildbot uses. You'll need to understand how the Buildbot sees the world to configure it properly.

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3.1 Version Control Systems

These source trees come from a Version Control System of some kind. CVS and Subversion are two popular ones, but the Buildbot supports others. All VC systems have some notion of an upstream repository which acts as a server2, from which clients can obtain source trees according to various parameters. The VC repository provides source trees of various projects, for different branches, and from various points in time. The first thing we have to do is to specify which source tree we want to get.

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3.1.1 Generalizing VC Systems

For the purposes of the Buildbot, we will try to generalize all VC systems as having repositories that each provide sources for a variety of projects. Each project is defined as a directory tree with source files. The individual files may each have revisions, but we ignore that and treat the project as a whole as having a set of revisions. Each time someone commits a change to the project, a new revision becomes available. These revisions can be described by a tuple with two items: the first is a branch tag, and the second is some kind of timestamp or revision stamp. Complex projects may have multiple branch tags, but there is always a default branch. The timestamp may be an actual timestamp (such as the -D option to CVS), or it may be a monotonically-increasing transaction number (such as the change number used by SVN and P4, or the revision number used by Arch, or a labeled tag used in CVS)3. The SHA1 revision ID used by Monotone and Mercurial is also a kind of revision stamp, in that it specifies a unique copy of the source tree, as does a Darcs “context” file.

When we aren't intending to make any changes to the sources we check out (at least not any that need to be committed back upstream), there are two basic ways to use a VC system:

Build personnel or CM staff typically use the first approach: the build that results is (ideally) completely specified by the two parameters given to the VC system: repository and revision tag. This gives QA and end-users something concrete to point at when reporting bugs. Release engineers are also reportedly fond of shipping code that can be traced back to a concise revision tag of some sort.

Developers are more likely to use the second approach: each morning the developer does an update to pull in the changes committed by the team over the last day. These builds are not easy to fully specify: it depends upon exactly when you did a checkout, and upon what local changes the developer has in their tree. Developers do not normally tag each build they produce, because there is usually significant overhead involved in creating these tags. Recreating the trees used by one of these builds can be a challenge. Some VC systems may provide implicit tags (like a revision number), while others may allow the use of timestamps to mean “the state of the tree at time X” as opposed to a tree-state that has been explicitly marked.

The Buildbot is designed to help developers, so it usually works in terms of the latest sources as opposed to specific tagged revisions. However, it would really prefer to build from reproducible source trees, so implicit revisions are used whenever possible.

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3.1.2 Source Tree Specifications

So for the Buildbot's purposes we treat each VC system as a server which can take a list of specifications as input and produce a source tree as output. Some of these specifications are static: they are attributes of the builder and do not change over time. Others are more variable: each build will have a different value. The repository is changed over time by a sequence of Changes, each of which represents a single developer making changes to some set of files. These Changes are cumulative4.

For normal builds, the Buildbot wants to get well-defined source trees that contain specific Changes, and exclude other Changes that may have occurred after the desired ones. We assume that the Changes arrive at the buildbot (through one of the mechanisms described in see Change Sources) in the same order in which they are committed to the repository. The Buildbot waits for the tree to become “stable” before initiating a build, for two reasons. The first is that developers frequently make multiple related commits in quick succession, even when the VC system provides ways to make atomic transactions involving multiple files at the same time. Running a build in the middle of these sets of changes would use an inconsistent set of source files, and is likely to fail (and is certain to be less useful than a build which uses the full set of changes). The tree-stable-timer is intended to avoid these useless builds that include some of the developer's changes but not all. The second reason is that some VC systems (i.e. CVS) do not provide repository-wide transaction numbers, so that timestamps are the only way to refer to a specific repository state. These timestamps may be somewhat ambiguous, due to processing and notification delays. By waiting until the tree has been stable for, say, 10 minutes, we can choose a timestamp from the middle of that period to use for our source checkout, and then be reasonably sure that any clock-skew errors will not cause the build to be performed on an inconsistent set of source files.

The Schedulers always use the tree-stable-timer, with a timeout that is configured to reflect a reasonable tradeoff between build latency and change frequency. When the VC system provides coherent repository-wide revision markers (such as Subversion's revision numbers, or in fact anything other than CVS's timestamps), the resulting Build is simply performed against a source tree defined by that revision marker. When the VC system does not provide this, a timestamp from the middle of the tree-stable period is used to generate the source tree5.

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3.1.3 How Different VC Systems Specify Sources

For CVS, the static specifications are repository and module. In addition to those, each build uses a timestamp (or omits the timestamp to mean the latest) and branch tag (which defaults to HEAD). These parameters collectively specify a set of sources from which a build may be performed.

Subversion combines the repository, module, and branch into a single Subversion URL parameter. Within that scope, source checkouts can be specified by a numeric revision number (a repository-wide monotonically-increasing marker, such that each transaction that changes the repository is indexed by a different revision number), or a revision timestamp. When branches are used, the repository and module form a static baseURL, while each build has a revision number and a branch (which defaults to a statically-specified defaultBranch). The baseURL and branch are simply concatenated together to derive the svnurl to use for the checkout.

Perforce is similar. The server is specified through a P4PORT parameter. Module and branch are specified in a single depot path, and revisions are depot-wide. When branches are used, the p4base and defaultBranch are concatenated together to produce the depot path.

Arch and Bazaar specify a repository by URL, as well as a version which is kind of like a branch name. Arch uses the word archive to represent the repository. Arch lets you push changes from one archive to another, removing the strict centralization required by CVS and SVN. It retains the distinction between repository and working directory that most other VC systems use. For complex multi-module directory structures, Arch has a built-in build config layer with which the checkout process has two steps. First, an initial bootstrap checkout is performed to retrieve a set of build-config files. Second, one of these files is used to figure out which archives/modules should be used to populate subdirectories of the initial checkout.

Builders which use Arch and Bazaar therefore have a static archive url, and a default “branch” (which is a string that specifies a complete category–branch–version triple). Each build can have its own branch (the category–branch–version string) to override the default, as well as a revision number (which is turned into a –patch-NN suffix when performing the checkout).

Darcs doesn't really have the notion of a single master repository. Nor does it really have branches. In Darcs, each working directory is also a repository, and there are operations to push and pull patches from one of these repositories to another. For the Buildbot's purposes, all you need to do is specify the URL of a repository that you want to build from. The build slave will then pull the latest patches from that repository and build them. Multiple branches are implemented by using multiple repositories (possibly living on the same server).

Builders which use Darcs therefore have a static repourl which specifies the location of the repository. If branches are being used, the source Step is instead configured with a baseURL and a defaultBranch, and the two strings are simply concatenated together to obtain the repository's URL. Each build then has a specific branch which replaces defaultBranch, or just uses the default one. Instead of a revision number, each build can have a “context”, which is a string that records all the patches that are present in a given tree (this is the output of darcs changes --context, and is considerably less concise than, e.g. Subversion's revision number, but the patch-reordering flexibility of Darcs makes it impossible to provide a shorter useful specification).

Mercurial is like Darcs, in that each branch is stored in a separate repository. The repourl, baseURL, and defaultBranch arguments are all handled the same way as with Darcs. The “revision”, however, is the hash identifier returned by hg identify.

Previous: How Different VC Systems Specify Sources, Up: Version Control Systems

3.1.4 Attributes of Changes


Each Change has a who attribute, which specifies which developer is responsible for the change. This is a string which comes from a namespace controlled by the VC repository. Frequently this means it is a username on the host which runs the repository, but not all VC systems require this (Arch, for example, uses a fully-qualified Arch ID, which looks like an email address, as does Darcs). Each StatusNotifier will map the who attribute into something appropriate for their particular means of communication: an email address, an IRC handle, etc.


It also has a list of files, which are just the tree-relative filenames of any files that were added, deleted, or modified for this Change. These filenames are used by the isFileImportant function (in the Scheduler) to decide whether it is worth triggering a new build or not, e.g. the function could use filename.endswith(".c") to only run a build if a C file were checked in. Certain BuildSteps can also use the list of changed files to run a more targeted series of tests, e.g. the python_twisted.Trial step can run just the unit tests that provide coverage for the modified .py files instead of running the full test suite.


The Change also has a comments attribute, which is a string containing any checkin comments.


Each Change can have a revision attribute, which describes how to get a tree with a specific state: a tree which includes this Change (and all that came before it) but none that come after it. If this information is unavailable, the .revision attribute will be None. These revisions are provided by the ChangeSource, and consumed by the computeSourceRevision method in the appropriate step.Source class.

revision is an int, seconds since the epoch
revision is an int, a transation number (r%d)
revision is a large string, the output of darcs changes --context
revision is a short string (a hash ID), the output of hg identify
revision is the full revision ID (ending in –patch-%d)
revision is an int, the transaction number


The Change might also have a branch attribute. This indicates that all of the Change's files are in the same named branch. The Schedulers get to decide whether the branch should be built or not.

For VC systems like CVS, Arch, and Monotone, the branch name is unrelated to the filename. (that is, the branch name and the filename inhabit unrelated namespaces). For SVN, branches are expressed as subdirectories of the repository, so the file's “svnurl” is a combination of some base URL, the branch name, and the filename within the branch. (In a sense, the branch name and the filename inhabit the same namespace). Darcs branches are subdirectories of a base URL just like SVN. Mercurial branches are the same as Darcs.

branch='warner-newfeature', files=['src/foo.c']
branch='branches/warner-newfeature', files=['src/foo.c']
branch='warner-newfeature', files=['src/foo.c']
branch='warner-newfeature', files=['src/foo.c']
branch='buildbot–usebranches–0', files=['buildbot/']


Finally, the Change might have a links list, which is intended to provide a list of URLs to a viewcvs-style web page that provides more detail for this Change, perhaps including the full file diffs.

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3.2 Schedulers

Each Buildmaster has a set of Scheduler objects, each of which gets a copy of every incoming Change. The Schedulers are responsible for deciding when Builds should be run. Some Buildbot installations might have a single Scheduler, while others may have several, each for a different purpose.

For example, a “quick” scheduler might exist to give immediate feedback to developers, hoping to catch obvious problems in the code that can be detected quickly. These typically do not run the full test suite, nor do they run on a wide variety of platforms. They also usually do a VC update rather than performing a brand-new checkout each time. You could have a “quick” scheduler which used a 30 second timeout, and feeds a single “quick” Builder that uses a VC mode='update' setting.

A separate “full” scheduler would run more comprehensive tests a little while later, to catch more subtle problems. This scheduler would have a longer tree-stable-timer, maybe 30 minutes, and would feed multiple Builders (with a mode= of 'copy', 'clobber', or 'export').

The tree-stable-timer and isFileImportant decisions are made by the Scheduler. Dependencies are also implemented here. Periodic builds (those which are run every N seconds rather than after new Changes arrive) are triggered by a special Periodic Scheduler subclass. The default Scheduler class can also be told to watch for specific branches, ignoring Changes on other branches. This may be useful if you have a trunk and a few release branches which should be tracked, but when you don't want to have the Buildbot pay attention to several dozen private user branches.

Some Schedulers may trigger builds for other reasons, other than recent Changes. For example, a Scheduler subclass could connect to a remote buildmaster and watch for builds of a library to succeed before triggering a local build that uses that library.

Each Scheduler creates and submits BuildSet objects to the BuildMaster, which is then responsible for making sure the individual BuildRequests are delivered to the target Builders.

Scheduler instances are activated by placing them in the c['schedulers'] list in the buildmaster config file. Each Scheduler has a unique name.

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3.3 BuildSet

A BuildSet is the name given to a set of Builds that all compile/test the same version of the tree on multiple Builders. In general, all these component Builds will perform the same sequence of Steps, using the same source code, but on different platforms or against a different set of libraries.

The BuildSet is tracked as a single unit, which fails if any of the component Builds have failed, and therefore can succeed only if all of the component Builds have succeeded. There are two kinds of status notification messages that can be emitted for a BuildSet: the firstFailure type (which fires as soon as we know the BuildSet will fail), and the Finished type (which fires once the BuildSet has completely finished, regardless of whether the overall set passed or failed).

A BuildSet is created with a source stamp tuple of (branch, revision, changes, patch), some of which may be None, and a list of Builders on which it is to be run. They are then given to the BuildMaster, which is responsible for creating a separate BuildRequest for each Builder.

There are a couple of different likely values for the SourceStamp:

(revision=None, changes=[CHANGES], patch=None)
This is a SourceStamp used when a series of Changes have triggered a build. The VC step will attempt to check out a tree that contains CHANGES (and any changes that occurred before CHANGES, but not any that occurred after them).
(revision=None, changes=None, patch=None)
This builds the most recent code on the default branch. This is the sort of SourceStamp that would be used on a Build that was triggered by a user request, or a Periodic scheduler. It is also possible to configure the VC Source Step to always check out the latest sources rather than paying attention to the Changes in the SourceStamp, which will result in same behavior as this.
(branch=BRANCH, revision=None, changes=None, patch=None)
This builds the most recent code on the given BRANCH. Again, this is generally triggered by a user request or Periodic build.
(revision=REV, changes=None, patch=(LEVEL, DIFF))
This checks out the tree at the given revision REV, then applies a patch (using diff -pLEVEL <DIFF). The try feature uses this kind of SourceStamp. If patch is None, the patching step is bypassed.

The buildmaster is responsible for turning the BuildSet into a set of BuildRequest objects and queueing them on the appropriate Builders.

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3.4 BuildRequest

A BuildRequest is a request to build a specific set of sources on a single specific Builder. Each Builder runs the BuildRequest as soon as it can (i.e. when an associated buildslave becomes free).

The BuildRequest contains the SourceStamp specification. The actual process of running the build (the series of Steps that will be executed) is implemented by the Build object. In this future this might be changed, to have the Build define what gets built, and a separate BuildProcess (provided by the Builder) to define how it gets built.

The BuildRequest may be mergeable with other compatible BuildRequests. Builds that are triggered by incoming Changes will generally be mergeable. Builds that are triggered by user requests are generally not, unless they are multiple requests to build the latest sources of the same branch.

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3.5 Builder

The Builder is a long-lived object which controls all Builds of a given type. Each one is created when the config file is first parsed, and lives forever (or rather until it is removed from the config file). It mediates the connections to the buildslaves that do all the work, and is responsible for creating the Build objects that decide how a build is performed (i.e., which steps are executed in what order).

Each Builder gets a unique name, and the path name of a directory where it gets to do all its work (there is a buildmaster-side directory for keeping status information, as well as a buildslave-side directory where the actual checkout/compile/test commands are executed). It also gets a BuildFactory, which is responsible for creating new Build instances: because the Build instance is what actually performs each build, choosing the BuildFactory is the way to specify what happens each time a build is done.

Each Builder is associated with one of more BuildSlaves. A Builder which is used to perform OS-X builds (as opposed to Linux or Solaris builds) should naturally be associated with an OS-X-based buildslave.

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3.6 Users

Buildbot has a somewhat limited awareness of users. It assumes the world consists of a set of developers, each of whom can be described by a couple of simple attributes. These developers make changes to the source code, causing builds which may succeed or fail.

Each developer is primarily known through the source control system. Each Change object that arrives is tagged with a who field that typically gives the account name (on the repository machine) of the user responsible for that change. This string is the primary key by which the User is known, and is displayed on the HTML status pages and in each Build's “blamelist”.

To do more with the User than just refer to them, this username needs to be mapped into an address of some sort. The responsibility for this mapping is left up to the status module which needs the address. The core code knows nothing about email addresses or IRC nicknames, just user names.

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3.6.1 Doing Things With Users

Each Change has a single User who is responsible for that Change. Most Builds have a set of Changes: the Build represents the first time these Changes have been built and tested by the Buildbot. The build has a “blamelist” that consists of a simple union of the Users responsible for all the Build's Changes.

The Build provides (through the IBuildStatus interface) a list of Users who are “involved” in the build. For now this is equal to the blamelist, but in the future it will be expanded to include a “build sheriff” (a person who is “on duty” at that time and responsible for watching over all builds that occur during their shift), as well as per-module owners who simply want to keep watch over their domain (chosen by subdirectory or a regexp matched against the filenames pulled out of the Changes). The Involved Users are those who probably have an interest in the results of any given build.

In the future, Buildbot will acquire the concept of “Problems”, which last longer than builds and have beginnings and ends. For example, a test case which passed in one build and then failed in the next is a Problem. The Problem lasts until the test case starts passing again, at which point the Problem is said to be “resolved”.

If there appears to be a code change that went into the tree at the same time as the test started failing, that Change is marked as being resposible for the Problem, and the user who made the change is added to the Problem's “Guilty” list. In addition to this user, there may be others who share responsibility for the Problem (module owners, sponsoring developers). In addition to the Responsible Users, there may be a set of Interested Users, who take an interest in the fate of the Problem.

Problems therefore have sets of Users who may want to be kept aware of the condition of the problem as it changes over time. If configured, the Buildbot can pester everyone on the Responsible list with increasing harshness until the problem is resolved, with the most harshness reserved for the Guilty parties themselves. The Interested Users may merely be told when the problem starts and stops, as they are not actually responsible for fixing anything.

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3.6.2 Email Addresses

The buildbot.status.mail.MailNotifier class provides a status target which can send email about the results of each build. It accepts a static list of email addresses to which each message should be delivered, but it can also be configured to send mail to the Build's Interested Users. To do this, it needs a way to convert User names into email addresses.

For many VC systems, the User Name is actually an account name on the system which hosts the repository. As such, turning the name into an email address is a simple matter of appending “”. Some projects use other kinds of mappings (for example the preferred email address may be at “” despite the repository host being named “”), and some VC systems have full separation between the concept of a user and that of an account on the repository host (like Perforce). Some systems (like Arch) put a full contact email address in every change.

To convert these names to addresses, the MailNotifier uses an EmailLookup object. This provides a .getAddress method which accepts a name and (eventually) returns an address. The default MailNotifier module provides an EmailLookup which simply appends a static string, configurable when the notifier is created. To create more complex behaviors (perhaps using an LDAP lookup, or using “finger” on a central host to determine a preferred address for the developer), provide a different object as the lookup argument.

In the future, when the Problem mechanism has been set up, the Buildbot will need to send mail to arbitrary Users. It will do this by locating a MailNotifier-like object among all the buildmaster's status targets, and asking it to send messages to various Users. This means the User-to-address mapping only has to be set up once, in your MailNotifier, and every email message the buildbot emits will take advantage of it.

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3.6.3 IRC Nicknames

Like MailNotifier, the buildbot.status.words.IRC class provides a status target which can announce the results of each build. It also provides an interactive interface by responding to online queries posted in the channel or sent as private messages.

In the future, the buildbot can be configured map User names to IRC nicknames, to watch for the recent presence of these nicknames, and to deliver build status messages to the interested parties. Like MailNotifier does for email addresses, the IRC object will have an IRCLookup which is responsible for nicknames. The mapping can be set up statically, or it can be updated by online users themselves (by claiming a username with some kind of “buildbot: i am user warner” commands).

Once the mapping is established, the rest of the buildbot can ask the IRC object to send messages to various users. It can report on the likelihood that the user saw the given message (based upon how long the user has been inactive on the channel), which might prompt the Problem Hassler logic to send them an email message instead.

Previous: IRC Nicknames, Up: Users

3.6.4 Live Status Clients

The Buildbot also offers a PB-based status client interface which can display real-time build status in a GUI panel on the developer's desktop. This interface is normally anonymous, but it could be configured to let the buildmaster know which developer is using the status client. The status client could then be used as a message-delivery service, providing an alternative way to deliver low-latency high-interruption messages to the developer (like “hey, you broke the build”).

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4 Configuration

The buildbot's behavior is defined by the “config file”, which normally lives in the master.cfg file in the buildmaster's base directory (but this can be changed with an option to the buildbot create-master command). This file completely specifies which Builders are to be run, which slaves they should use, how Changes should be tracked, and where the status information is to be sent. The buildmaster's buildbot.tac file names the base directory; everything else comes from the config file.

A sample config file was installed for you when you created the buildmaster, but you will need to edit it before your buildbot will do anything useful.

This chapter gives an overview of the format of this file and the various sections in it. You will need to read the later chapters to understand how to fill in each section properly.

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4.1 Config File Format

The config file is, fundamentally, just a piece of Python code which defines a dictionary named BuildmasterConfig, with a number of keys that are treated specially. You don't need to know Python to do basic configuration, though, you can just copy the syntax of the sample file. If you are comfortable writing Python code, however, you can use all the power of a full programming language to achieve more complicated configurations.

The BuildmasterConfig name is the only one which matters: all other names defined during the execution of the file are discarded. When parsing the config file, the Buildmaster generally compares the old configuration with the new one and performs the minimum set of actions necessary to bring the buildbot up to date: Builders which are not changed are left untouched, and Builders which are modified get to keep their old event history.

Basic Python syntax: comments start with a hash character (“#”), tuples are defined with (parenthesis, pairs), arrays are defined with [square, brackets], tuples and arrays are mostly interchangeable. Dictionaries (data structures which map “keys” to “values”) are defined with curly braces: {'key1': 'value1', 'key2': 'value2'} . Function calls (and object instantiation) can use named parameters, like w = html.Waterfall(http_port=8010).

The config file starts with a series of import statements, which make various kinds of Steps and Status targets available for later use. The main BuildmasterConfig dictionary is created, then it is populated with a variety of keys. These keys are broken roughly into the following sections, each of which is documented in the rest of this chapter:

The config file can use a few names which are placed into its namespace:

the base directory for the buildmaster. This string has not been expanded, so it may start with a tilde. It needs to be expanded before use. The config file is located in os.path.expanduser(os.path.join(basedir, 'master.cfg'))

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4.2 Loading the Config File

The config file is only read at specific points in time. It is first read when the buildmaster is launched. Once it is running, there are various ways to ask it to reload the config file. If you are on the system hosting the buildmaster, you can send a SIGHUP signal to it: the buildbot tool has a shortcut for this:

     buildbot reconfig BASEDIR

This command will show you all of the lines from twistd.log that relate to the reconfiguration. If there are any problems during the config-file reload, they will be displayed in these lines.

The debug tool (buildbot debugclient --master HOST:PORT) has a “Reload .cfg” button which will also trigger a reload. In the future, there will be other ways to accomplish this step (probably a password-protected button on the web page, as well as a privileged IRC command).

When reloading the config file, the buildmaster will endeavor to change as little as possible about the running system. For example, although old status targets may be shut down and new ones started up, any status targets that were not changed since the last time the config file was read will be left running and untouched. Likewise any Builders which have not been changed will be left running. If a Builder is modified (say, the build process is changed) while a Build is currently running, that Build will keep running with the old process until it completes. Any previously queued Builds (or Builds which get queued after the reconfig) will use the new process.

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4.3 Defining the Project

There are a couple of basic settings that you use to tell the buildbot what project it is working on. This information is used by status reporters to let users find out more about the codebase being exercised by this particular Buildbot installation.

     c['projectName'] = "Buildbot"
     c['projectURL'] = ""
     c['buildbotURL'] = "http://localhost:8010/"

projectName is a short string will be used to describe the project that this buildbot is working on. For example, it is used as the title of the waterfall HTML page.

projectURL is a string that gives a URL for the project as a whole. HTML status displays will show projectName as a link to projectURL, to provide a link from buildbot HTML pages to your project's home page.

The buildbotURL string should point to the location where the buildbot's internal web server (usually the html.Waterfall page) is visible. This typically uses the port number set when you create the Waterfall object: the buildbot needs your help to figure out a suitable externally-visible host name.

When status notices are sent to users (either by email or over IRC), buildbotURL will be used to create a URL to the specific build or problem that they are being notified about. It will also be made available to queriers (over IRC) who want to find out where to get more information about this buildbot.

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4.4 Listing Change Sources and Schedulers

The c['sources'] key is a list of ChangeSource instances6. This defines how the buildmaster learns about source code changes. More information about what goes here is available in See Getting Source Code Changes.

     import buildbot.changes.pb
     c['sources'] = [buildbot.changes.pb.PBChangeSource()]

c['schedulers'] is a list of Scheduler instances, each of which causes builds to be started on a particular set of Builders. The two basic Scheduler classes you are likely to start with are Scheduler and Periodic, but you can write a customized subclass to implement more complicated build scheduling.

The docstring for buildbot.scheduler.Scheduler is the best place to see all the options that can be used. Type pydoc buildbot.scheduler.Scheduler to see it, or look in buildbot/ directly.

The basic Scheduler takes four arguments:

Each Scheduler must have a unique name. This is only used in status displays.
This Scheduler will pay attention to a single branch, ignoring Changes that occur on other branches. Setting branch equal to the special value of None means it should only pay attention to the default branch. Note that None is a keyword, not a string, so you want to use None and not "None".
The Scheduler will wait for this many seconds before starting the build. If new changes are made during this interval, the timer will be restarted, so really the build will be started after a change and then after this many seconds of inactivity.
When the tree-stable-timer finally expires, builds will be started on these Builders. Each Builder gets a unique name: these strings must match.
     from buildbot import scheduler
     quick = scheduler.Scheduler("quick", None, 60,
                                 ["quick-linux", "quick-netbsd"])
     full = scheduler.Scheduler("full", None, 5*60,
                                ["full-linux", "full-netbsd", "full-OSX"])
     nightly = scheduler.Periodic("nightly", ["full-solaris"], 24*60*60)
     c['schedulers'] = [quick, full, nightly]

In this example, the two “quick” builds are triggered 60 seconds after the tree has been changed. The “full” builds do not run quite so quickly (they wait 5 minutes), so hopefully if the quick builds fail due to a missing file or really simple typo, the developer can discover and fix the problem before the full builds are started. Both Schedulers only pay attention to the default branch: any changes on other branches are ignored by these Schedulers. Each Scheduler triggers a different set of Builders, referenced by name.

The third Scheduler in this example just runs the full solaris build once per day. (note that this Scheduler only lets you control the time between builds, not the absolute time-of-day of each Build, so this could easily wind up a “daily” or “every afternoon” scheduler depending upon when it was first activated).

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4.4.1 Scheduler Types

Here is a brief catalog of the available Scheduler types. All these Schedulers are classes in buildbot.scheduler, and the docstrings there are the best source of documentation on the arguments taken by each one.

This is the default Scheduler class. It follows exactly one branch, and starts a configurable tree-stable-timer after each change on that branch. When the timer expires, it starts a build on some set of Builders. The Scheduler accepts a fileIsImportant function which can be used to ignore some Changes if they do not affect any “important” files.
This scheduler uses a tree-stable-timer like the default one, but follows multiple branches at once. Each branch gets a separate timer.
This scheduler watches an “upstream” Builder. When that Builder successfully builds a particular set of Changes, it triggers builds of the same code on a configured set of “downstream” builders. The next section (see Build Dependencies) describes this scheduler in more detail.
This simple scheduler just triggers a build every N seconds.
This is highly configurable periodic build scheduler, which triggers a build at particular times of day, week, month, or year. The configuration syntax is very similar to the well-known crontab format, in which you provide values for minute, hour, day, and month (some of which can be wildcards), and a build is triggered whenever the current time matches the given constraints. This can run a build every night, every morning, every weekend, alternate Thursdays, on your boss's birthday, etc.
Try_Jobdir / Try_Userpass
This scheduler allows developers to use the buildbot try command to trigger builds of code they have not yet committed. See try for complete details.

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4.4.2 Build Dependencies

It is common to wind up with one kind of build which should only be performed if the same source code was successfully handled by some other kind of build first. An example might be a packaging step: you might only want to produce .deb or RPM packages from a tree that was known to compile successfully and pass all unit tests. You could put the packaging step in the same Build as the compile and testing steps, but there might be other reasons to not do this (in particular you might have several Builders worth of compiles/tests, but only wish to do the packaging once). Another example is if you want to skip the “full” builds after a failing “quick” build of the same source code. Or, if one Build creates a product (like a compiled library) that is used by some other Builder, you'd want to make sure the consuming Build is run after the producing one.

You can use Dependencies to express this relationship to the Buildbot. There is a special kind of Scheduler named scheduler.Dependent that will watch an “upstream” Scheduler for builds to complete successfully (on all of its Builders). Each time that happens, the same source code (i.e. the same SourceStamp) will be used to start a new set of builds, on a different set of Builders. This “downstream” scheduler doesn't pay attention to Changes at all, it only pays attention to the upstream scheduler.

If the SourceStamp fails on any of the Builders in the upstream set, the downstream builds will not fire.

     from buildbot import scheduler
     tests = scheduler.Scheduler("tests", None, 5*60,
                                 ["full-linux", "full-netbsd", "full-OSX"])
     package = scheduler.Dependent("package",
                                   tests, # upstream scheduler
                                   ["make-tarball", "make-deb", "make-rpm"])
     c['schedulers'] = [tests, package]

Note that Dependent's upstream scheduler argument is given as a Scheduler instance, not a name. This makes it impossible to create circular dependencies in the config file.

Next: , Previous: Listing Change Sources and Schedulers, Up: Configuration

4.5 Setting the slaveport

The buildmaster will listen on a TCP port of your choosing for connections from buildslaves. It can also use this port for connections from remote Change Sources, status clients, and debug tools. This port should be visible to the outside world, and you'll need to tell your buildslave admins about your choice.

It does not matter which port you pick, as long it is externally visible, however you should probably use something larger than 1024, since most operating systems don't allow non-root processes to bind to low-numbered ports. If your buildmaster is behind a firewall or a NAT box of some sort, you may have to configure your firewall to permit inbound connections to this port.

     c['slavePortnum'] = 10000

c['slavePortnum'] is a strports specification string, defined in the twisted.application.strports module (try pydoc twisted.application.strports to get documentation on the format). This means that you can have the buildmaster listen on a localhost-only port by doing:

     c['slavePortnum'] = "tcp:10000:interface="

This might be useful if you only run buildslaves on the same machine, and they are all configured to contact the buildmaster at localhost:10000.

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4.6 Buildslave Specifiers

The c['bots'] key is a list of known buildslaves. Each buildslave is defined by a tuple of (slavename, slavepassword). These are the same two values that need to be provided to the buildslave administrator when they create the buildslave.

     c['bots'] = [('bot-solaris', 'solarispasswd'),
                  ('bot-bsd', 'bsdpasswd'),

The slavenames must be unique, of course. The password exists to prevent evildoers from interfering with the buildbot by inserting their own (broken) buildslaves into the system and thus displacing the real ones.

Buildslaves with an unrecognized slavename or a non-matching password will be rejected when they attempt to connect, and a message describing the problem will be put in the log file (see Logfiles).

Next: , Previous: Buildslave Specifiers, Up: Configuration

4.7 Defining Builders

The c['builders'] key is a list of dictionaries which specify the Builders. The Buildmaster runs a collection of Builders, each of which handles a single type of build (e.g. full versus quick), on a single build slave. A Buildbot which makes sure that the latest code (“HEAD”) compiles correctly across four separate architecture will have four Builders, each performing the same build but on different slaves (one per platform).

Each Builder gets a separate column in the waterfall display. In general, each Builder runs independently (although various kinds of interlocks can cause one Builder to have an effect on another).

Each Builder specification dictionary has several required keys:

This specifies the Builder's name, which is used in status reports.
This specifies which buildslave will be used by this Builder. slavename must appear in the c['bots'] list. Each buildslave can accomodate multiple Builders.
If you provide slavenames instead of slavename, you can give a list of buildslaves which are capable of running this Builder. If multiple buildslaves are available for any given Builder, you will have some measure of redundancy: in case one slave goes offline, the others can still keep the Builder working. In addition, multiple buildslaves will allow multiple simultaneous builds for the same Builder, which might be useful if you have a lot of forced or “try” builds taking place.

If you use this feature, it is important to make sure that the buildslaves are all, in fact, capable of running the given build. The slave hosts should be configured similarly, otherwise you will spend a lot of time trying (unsuccessfully) to reproduce a failure that only occurs on some of the buildslaves and not the others. Different platforms, operating systems, versions of major programs or libraries, all these things mean you should use separate Builders.

This specifies the name of a subdirectory (under the base directory) in which everything related to this builder will be placed. On the buildmaster, this holds build status information. On the buildslave, this is where checkouts, compiles, and tests are run.
This is a buildbot.process.factory.BuildFactory instance which controls how the build is performed. Full details appear in their own chapter, See Build Process. Parameters like the location of the CVS repository and the compile-time options used for the build are generally provided as arguments to the factory's constructor.

Other optional keys may be set on each Builder:

If provided, this is a string that identifies a category for the builder to be a part of. Status clients can limit themselves to a subset of the available categories. A common use for this is to add new builders to your setup (for a new module, or for a new buildslave) that do not work correctly yet and allow you to integrate them with the active builders. You can put these new builders in a test category, make your main status clients ignore them, and have only private status clients pick them up. As soon as they work, you can move them over to the active category.

Next: , Previous: Defining Builders, Up: Configuration

4.8 Defining Status Targets

The Buildmaster has a variety of ways to present build status to various users. Each such delivery method is a “Status Target” object in the configuration's status list. To add status targets, you just append more objects to this list:

     c['status'] = []
     from buildbot.status import html
     from buildbot.status import mail
     m = mail.MailNotifier(fromaddr="buildbot@localhost",
     from buildbot.status import words
     c['status'].append(words.IRC(host="", nick="bb",

Status delivery has its own chapter, See Status Delivery, in which all the built-in status targets are documented.

Previous: Defining Status Targets, Up: Configuration

4.9 Debug options

If you set c['debugPassword'], then you can connect to the buildmaster with the diagnostic tool launched by buildbot debugclient MASTER:PORT. From this tool, you can reload the config file, manually force builds, and inject changes, which may be useful for testing your buildmaster without actually commiting changes to your repository (or before you have the Change Sources set up). The debug tool uses the same port number as the slaves do: c['slavePortnum'], and is authenticated with this password.

     c['debugPassword'] = "debugpassword"

If you set c['manhole'] to an instance of one of the classes in buildbot.manhole, you can telnet or ssh into the buildmaster and get an interactive Python shell, which may be useful for debugging buildbot internals. It is probably only useful for buildbot developers. It exposes full access to the buildmaster's account (including the ability to modify and delete files), so it should not be enabled with a weak or easily guessable password.

There are three separate Manhole classes. Two of them use SSH, one uses unencrypted telnet. Two of them use a username+password combination to grant access, one of them uses an SSH-style authorized_keys file which contains a list of ssh public keys.

You construct this with the name of a file that contains one SSH public key per line, just like ~/.ssh/authorized_keys. If you provide a non-absolute filename, it will be interpreted relative to the buildmaster's base directory.
This one accepts SSH connections but asks for a username and password when authenticating. It accepts only one such pair.
This accepts regular unencrypted telnet connections, and asks for a username/password pair before providing access. Because this username/password is transmitted in the clear, and because Manhole access to the buildmaster is equivalent to granting full shell privileges to both the buildmaster and all the buildslaves (and to all accounts which then run code produced by the buildslaves), it is highly recommended that you use one of the SSH manholes instead.
     # some examples:
     from buildbot import manhole
     c['manhole'] = manhole.AuthorizedKeysManhole(1234, "authorized_keys")
     c['manhole'] = manhole.PasswordManhole(1234, "alice", "mysecretpassword")
     c['manhole'] = manhole.TelnetManhole(1234, "bob", "snoop_my_password_please")

The Manhole instance can be configured to listen on a specific port. You may wish to have this listening port bind to the loopback interface (sometimes known as “lo0”, “localhost”, or to restrict access to clients which are running on the same host.

     from buildbot.manhole import PasswordManhole
     c['manhole'] = PasswordManhole("tcp:9999:interface=","admin","passwd")

To have the Manhole listen on all interfaces, use "tcp:9999" or simply 9999. This port specification uses twisted.application.strports, so you can make it listen on SSL or even UNIX-domain sockets if you want.

Note that using any Manhole requires that the TwistedConch package be installed, and that you be using Twisted version 2.0 or later.

The buildmaster's SSH server will use a different host key than the normal sshd running on a typical unix host. This will cause the ssh client to complain about a “host key mismatch”, because it does not realize there are two separate servers running on the same host. To avoid this, use a clause like the following in your .ssh/config file:

     Host remotehost-buildbot
      HostName remotehost
      HostKeyAlias remotehost-buildbot
      Port 9999
      # use 'user' if you use PasswordManhole and your name is not 'admin'.
      # if you use AuthorizedKeysManhole, this probably doesn't matter.
      User admin

Next: , Previous: Configuration, Up: Top

5 Getting Source Code Changes

The most common way to use the Buildbot is centered around the idea of Source Trees: a directory tree filled with source code of some form which can be compiled and/or tested. Some projects use languages that don't involve any compilation step: nevertheless there may be a build phase where files are copied or rearranged into a form that is suitable for installation. Some projects do not have unit tests, and the Buildbot is merely helping to make sure that the sources can compile correctly. But in all of these cases, the thing-being-tested is a single source tree.

A Version Control System mantains a source tree, and tells the buildmaster when it changes. The first step of each Build is typically to acquire a copy of some version of this tree.

This chapter describes how the Buildbot learns about what Changes have occurred. For more information on VC systems and Changes, see Version Control Systems.

Previous: Getting Source Code Changes, Up: Getting Source Code Changes

5.1 Change Sources

Each Buildmaster watches a single source tree. Changes can be provided by a variety of ChangeSource types, however any given project will typically have only a single ChangeSource active. This section provides a description of all available ChangeSource types and explains how to set up each of them.

There are a variety of ChangeSources available, some of which are meant to be used in conjunction with other tools to deliver Change events from the VC repository to the buildmaster.

As a quick guide, here is a list of VC systems and the ChangeSources that might be useful with them. All of these ChangeSources are in the buildbot.changes module.






All VC systems can be driven by a PBChangeSource and the buildbot sendchange tool run from some form of commit script. If you write an email parsing function, they can also all be driven by a suitable MaildirSource.

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5.1.1 Choosing ChangeSources

The master.cfg configuration file has a dictionary key named BuildmasterConfig['sources'], which holds a list of IChangeSource objects. The config file will typically create an object from one of the classes described below and stuff it into the list.

     s = FreshCVSSourceNewcred(host="host", port=4519,
                               user="alice", passwd="secret",
     BuildmasterConfig['sources'] = [s]

Each source tree has a nominal top. Each Change has a list of filenames, which are all relative to this top location. The ChangeSource is responsible for doing whatever is necessary to accomplish this. Most sources have a prefix argument: a partial pathname which is stripped from the front of all filenames provided to that ChangeSource. Files which are outside this sub-tree are ignored by the changesource: it does not generate Changes for those files.

Next: , Previous: Choosing ChangeSources, Up: Change Sources

5.1.2 CVSToys - PBService

The CVSToys package provides a server which runs on the machine that hosts the CVS repository it watches. It has a variety of ways to distribute commit notifications, and offers a flexible regexp-based way to filter out uninteresting changes. One of the notification options is named PBService and works by listening on a TCP port for clients. These clients subscribe to hear about commit notifications.

The buildmaster has a CVSToys-compatible PBService client built in. There are two versions of it, one for old versions of CVSToys (1.0.9 and earlier) which used the oldcred authentication framework, and one for newer versions (1.0.10 and later) which use newcred. Both are classes in the buildbot.changes.freshcvs package.

FreshCVSSourceNewcred objects are created with the following parameters:

host and port
these specify where the CVSToys server can be reached
user and passwd
these specify the login information for the CVSToys server (freshcvs). These must match the server's values, which are defined in the freshCfg configuration file (which lives in the CVSROOT directory of the repository).
this is the prefix to be found and stripped from filenames delivered by the CVSToys server. Most projects live in sub-directories of the main repository, as siblings of the CVSROOT sub-directory, so typically this prefix is set to that top sub-directory name.


To set up the freshCVS server, add a statement like the following to your freshCfg file:

     pb = ConfigurationSet([
         (None, None, None, PBService(userpass=('foo', 'bar'), port=4519)),

This will announce all changes to a client which connects to port 4519 using a username of 'foo' and a password of 'bar'.

Then add a clause like this to your buildmaster's master.cfg:

     BuildmasterConfig['sources'] = [FreshCVSSource("", 4519,
                                     "foo", "bar",

where "" is the host that is running the FreshCVS daemon, and "glib" is the top-level directory (relative to the repository's root) where all your source code lives. Most projects keep one or more projects in the same repository (along with CVSROOT/ to hold admin files like loginfo and freshCfg); the prefix= argument tells the buildmaster to ignore everything outside that directory, and to strip that common prefix from all pathnames it handles.

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5.1.3 CVSToys - mail notification

CVSToys also provides a MailNotification action which will send email to a list of recipients for each commit. This tends to work better than using /bin/mail from within the CVSROOT/loginfo file directly, as CVSToys will batch together all files changed during the same CVS invocation, and can provide more information (like creating a ViewCVS URL for each file changed).

The Buildbot's FCMaildirSource is a ChangeSource which knows how to parse these CVSToys messages and turn them into Change objects. It watches a Maildir for new messages. The usually installation process looks like:

  1. Create a mailing list, projectname-commits.
  2. In CVSToys' freshCfg file, use a MailNotification action to send commit mail to this mailing list.
  3. Subscribe the buildbot user to the mailing list.
  4. Configure your .qmail or .forward file to deliver these messages into a maildir.
  5. In the Buildbot's master.cfg file, use a FCMaildirSource to watch the maildir for commit messages.

The FCMaildirSource is created with two parameters: the directory name of the maildir root, and the prefix to strip.

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5.1.4 Other mail notification ChangeSources

There are other types of maildir-watching ChangeSources, which only differ in the function used to parse the message body.

SyncmailMaildirSource knows how to parse the message format used in mail sent by Syncmail.

BonsaiMaildirSource parses messages sent out by Bonsai.

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5.1.5 PBChangeSource

The last kind of ChangeSource actually listens on a TCP port for clients to connect and push change notices into the Buildmaster. This is used by the built-in buildbot sendchange notification tool, as well as the VC-specific contrib/ and contrib/ tools. These tools are run by the repository (in a commit hook script), and connect to the buildmaster directly each time a file is comitted. This is also useful for creating new kinds of change sources that work on a push model instead of some kind of subscription scheme, for example a script which is run out of an email .forward file.

This ChangeSource can be configured to listen on its own TCP port, or it can share the port that the buildmaster is already using for the buildslaves to connect. (This is possible because the PBChangeSource uses the same protocol as the buildslaves, and they can be distinguished by the username attribute used when the initial connection is established). It might be useful to have it listen on a different port if, for example, you wanted to establish different firewall rules for that port. You could allow only the SVN repository machine access to the PBChangeSource port, while allowing only the buildslave machines access to the slave port. Or you could just expose one port and run everything over it. Note: this feature is not yet implemented, the PBChangeSource will always share the slave port and will always have a user name of change, and a passwd of changepw. These limitations will be removed in the future..

The PBChangeSource is created with the following arguments. All are optional.

which port to listen on. If None (which is the default), it shares the port used for buildslave connections. Not Implemented, always set to None.
user and passwd
The user/passwd account information that the client program must use to connect. Defaults to change and changepw. Not Implemented, user is currently always set to change, passwd is always set to changepw.
The prefix to be found and stripped from filenames delivered over the connection. Any filenames which do not start with this prefix will be removed. If all the filenames in a given Change are removed, the that whole Change will be dropped. This string should probably end with a directory separator.

This is useful for changes coming from version control systems that represent branches as parent directories within the repository (like SVN and Perforce). Use a prefix of 'trunk/' or 'project/branches/foobranch/' to only follow one branch and to get correct tree-relative filenames. Without a prefix, the PBChangeSource will probably deliver Changes with filenames like trunk/foo.c instead of just foo.c. Of course this also depends upon the tool sending the Changes in (like buildbot sendchange) and what filenames it is delivering: that tool may be filtering and stripping prefixes at the sending end.

Next: , Previous: PBChangeSource, Up: Change Sources

5.1.6 P4Source

The P4Source periodically polls a Perforce depot for changes. It accepts the following arguments:

The base depot path to watch, without the trailing '/...'.
The Perforce server to connect to (as host:port).
The Perforce user.
The Perforce password.
A function that maps a pathname, without the leading p4base, to a (branch, filename) tuple. The default just returns (None, branchfile), which effectively disables branch support. You should supply a function which understands your repository structure.
How often to poll, in seconds. Defaults to 600 (10 minutes).
The maximum number of changes to inspect at a time. If more than this number occur since the last poll, older changes will be silently ignored.


This configuration uses the P4PORT, P4USER, and P4PASSWD specified in the buildmaster's environment. It watches a project in which the branch name is simply the next path component, and the file is all path components after.

     import buildbot.changes.p4poller
             split_file=lambda branchfile: branchfile.split('/',1)

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5.1.7 BonsaiPoller

The BonsaiPoller periodically polls a Bonsai server. This is a CGI script accessed through a web server that provides information about a CVS tree, for example the Mozilla bonsai server at Bonsai servers are usable by both humans and machines. In this case, the buildbot's change source forms a query which asks about any files in the specified branch which have changed since the last query.

Please take a look at the BonsaiPoller docstring for details about the arguments it accepts.

Previous: BonsaiPoller, Up: Change Sources

5.1.8 SVNPoller

The buildbot.changes.svnpoller.SVNPoller is a ChangeSource which periodically polls a Subversion repository for new revisions, by running the svn log command in a subshell. It can watch a single branch or multiple branches.

SVNPoller accepts the following arguments:

The base URL path to watch, like svn://, or, or even file:///home/svn/Repository/ProjectA/branches/1.5/. This must include the access scheme, the location of the repository (both the hostname for remote ones, and any additional directory names necessary to get to the repository), and the sub-path within the repository's virtual filesystem for the project and branch of interest.

The SVNPoller will only pay attention to files inside the subdirectory specified by the complete svnurl.

A function to convert pathnames into (branch, relative_pathname) tuples. Use this to explain your repository's branch-naming policy to SVNPoller. This function must accept a single string and return a two-entry tuple. There are a few utility functions in buildbot.changes.svnpoller that can be used as a split_file function, see below for details.

The default value always returns (None, path), which indicates that all files are on the trunk.

Subclasses of SVNPoller can override the split_file method instead of using the split_file= argument.

An optional string parameter. If set, the --user argument will be added to all svn commands. Use this if you have to authenticate to the svn server before you can do svn info or svn log commands.
Like svnuser, this will cause a --password argument to be passed to all svn commands.
How often to poll, in seconds. Defaults to 600 (checking once every 10 minutes). Lower this if you want the buildbot to notice changes faster, raise it if you want to reduce the network and CPU load on your svn server. Please be considerate of public SVN repositories by using a large interval when polling them.
The maximum number of changes to inspect at a time. Every POLLINTERVAL seconds, the SVNPoller asks for the last HISTMAX changes and looks through them for any ones it does not already know about. If more than HISTMAX revisions have been committed since the last poll, older changes will be silently ignored. Larger values of histmax will cause more time and memory to be consumed on each poll attempt. histmax defaults to 100.
This controls the svn executable to use. If subversion is installed in a weird place on your system (outside of the buildmaster's $PATH), use this to tell SVNPoller where to find it. The default value of “svn” will almost always be sufficient.


Each source file that is tracked by a Subversion repository has a fully-qualified SVN URL in the following form: (REPOURL)(PROJECT-plus-BRANCH)(FILEPATH). When you create the SVNPoller, you give it a svnurl value that includes all of the REPOURL and possibly some portion of the PROJECT-plus-BRANCH string. The SVNPoller is responsible for producing Changes that contain a branch name and a FILEPATH (which is relative to the top of a checked-out tree). The details of how these strings are split up depend upon how your repository names its branches.


One common layout is to have all the various projects that share a repository get a single top-level directory each. Then under a given project's directory, you get two subdirectories, one named “trunk” and another named “branches”. Under “branches” you have a bunch of other directories, one per branch, with names like “1.5.x” and “testing”. It is also common to see directories like “tags” and “releases” next to “branches” and “trunk”.

For example, the Twisted project has a subversion server on “” that hosts several sub-projects. The repository is available through a SCHEME of “svn:”. The primary sub-project is Twisted, of course, with a repository root of “svn://”. Another sub-project is Informant, with a root of “svn://”, etc. Inside any checked-out Twisted tree, there is a file named bin/trial (which is used to run unit test suites).

The trunk for Twisted is in “svn://”, and the fully-qualified SVN URL for the trunk version of trial would be “svn://”. The same SVNURL for that file on a branch named “1.5.x” would be “svn://”.

To set up a SVNPoller that watches the Twisted trunk (and nothing else), we would use the following:

     from buildbot.changes.svnpoller import SVNPoller
     s = SVNPoller("svn://")

In this case, every Change that our SVNPoller produces will have .branch=None, to indicate that the Change is on the trunk. No other sub-projects or branches will be tracked.

If we want our ChangeSource to follow multiple branches, we have to do two things. First we have to change our svnurl= argument to watch more than just “.../Twisted/trunk”. We will set it to “.../Twisted” so that we'll see both the trunk and all the branches. Second, we have to tell SVNPoller how to split the (PROJECT-plus-BRANCH)(FILEPATH) strings it gets from the repository out into (BRANCH) and (FILEPATH) pairs.

We do the latter by providing a “split_file” function. This function is responsible for splitting something like “branches/1.5.x/bin/trial” into branch=”branches/1.5.x” and filepath=”bin/trial”. This function is always given a string that names a file relative to the subdirectory pointed to by the SVNPoller's svnurl= argument. It is expected to return a (BRANCHNAME, FILEPATH) tuple (in which FILEPATH is relative to the branch indicated), or None to indicate that the file is outside any project of interest.

(note that we want to see “branches/1.5.x” rather than just “1.5.x” because when we perform the SVN checkout, we will probably append the branch name to the baseURL, which requires that we keep the “branches” component in there. Other VC schemes use a different approach towards branches and may not require this artifact.)

If your repository uses this same PROJECT/BRANCH/FILEPATH naming scheme, the following function will work:

     def split_file_branches(path):
         pieces = path.split('/')
         if pieces[0] == 'trunk':
             return (None, '/'.join(pieces[1:]))
         elif pieces[0] == 'branches':
             return ('/'.join(pieces[0:2]),
             return None

This function is provided as buildbot.changes.svnpoller.split_file_branches for your convenience. So to have our Twisted-watching SVNPoller follow multiple branches, we would use this:

     from buildbot.changes.svnpoller import SVNPoller, split_file_branches
     s = SVNPoller("svn://",

Changes for all sorts of branches (with names like “branches/1.5.x”, and None to indicate the trunk) will be delivered to the Schedulers. Each Scheduler is then free to use or ignore each branch as it sees fit.


Another common way to organize a Subversion repository is to put the branch name at the top, and the projects underneath. This is especially frequent when there are a number of related sub-projects that all get released in a group.

For example, hosts a project named “Nevow” as well as one named “Quotient”. In a checked-out Nevow tree there is a directory named “formless” that contains a python source file named “”. This repository is accessible via webdav (and thus uses an “http:” scheme) through the hostname. There are many branches in this repository, and they use a (BRANCHNAME)/(PROJECT) naming policy.

The fully-qualified SVN URL for the trunk version of is You can do an svn co with that URL and get a copy of the latest version. The 1.5.x branch version of this file would have a URL of The whole Nevow trunk would be checked out with, while the Quotient trunk would be checked out using

Now suppose we want to have an SVNPoller that only cares about the Nevow trunk. This case looks just like the PROJECT/BRANCH layout described earlier:

     from buildbot.changes.svnpoller import SVNPoller
     s = SVNPoller("")

But what happens when we want to track multiple Nevow branches? We have to point our svnurl= high enough to see all those branches, but we also don't want to include Quotient changes (since we're only building Nevow). To accomplish this, we must rely upon the split_file function to help us tell the difference between files that belong to Nevow and those that belong to Quotient, as well as figuring out which branch each one is on.

     from buildbot.changes.svnpoller import SVNPoller
     s = SVNPoller("",

The my_file_splitter function will be called with repository-relative pathnames like:

This is a Nevow file, on the trunk. We want the Change that includes this to see a filename of formless/", and a branch of None
This is a Nevow file, on a branch. We want to get branch=”branches/1.5.x” and filename=”formless/”.
This is a Quotient file, so we want to ignore it by having my_file_splitter return None.
This is also a Quotient file, which should be ignored.

The following definition for my_file_splitter will do the job:

     def my_file_splitter(path):
         pieces = path.split('/')
         if pieces[0] == 'trunk':
             branch = None
             pieces.pop(0) # remove 'trunk'
         elif pieces[0] == 'branches':
             pieces.pop(0) # remove 'branches'
             # grab branch name
             branch = 'branches/' + pieces.pop(0)
             return None # something weird
         projectname = pieces.pop(0)
         if projectname != 'Nevow':
             return None # wrong project
         return (branch, '/'.join(pieces))

Next: , Previous: Getting Source Code Changes, Up: Top

6 Build Process

A Build object is responsible for actually performing a build. It gets access to a remote SlaveBuilder where it may run commands, and a BuildStatus object where it must emit status events. The Build is created by the Builder's BuildFactory.

The default Build class is made up of a fixed sequence of BuildSteps, executed one after another until all are complete (or one of them indicates that the build should be halted early). The default BuildFactory creates instances of this Build class with a list of BuildSteps, so the basic way to configure the build is to provide a list of BuildSteps to your BuildFactory.

More complicated Build subclasses can make other decisions: execute some steps only if certain files were changed, or if certain previous steps passed or failed. The base class has been written to allow users to express basic control flow without writing code, but you can always subclass and customize to achieve more specialized behavior.

Next: , Previous: Build Process, Up: Build Process

6.1 Build Steps

BuildSteps are usually specified in the buildmaster's configuration file, in a list of “step specifications” that is used to create the BuildFactory. These “step specifications” are not actual steps, but rather a tuple of the BuildStep subclass to be created and a dictionary of arguments. (the actual BuildStep instances are not created until the Build is started, so that each Build gets an independent copy of each BuildStep). The preferred way to create these step specifications is with the BuildFactory's addStep method:

     from buildbot.steps import source, shell
     from buildbot.process import factory
     f = factory.BuildFactory()
     f.addStep(source.SVN, svnurl="")
     f.addStep(shell.ShellCommand, command=["make", "all"])
     f.addStep(shell.ShellCommand, command=["make", "test"])

The rest of this section lists all the standard BuildStep objects available for use in a Build, and the parameters which can be used to control each.

Next: , Previous: Build Steps, Up: Build Steps

6.1.1 Common Parameters

The standard Build runs a series of BuildSteps in order, only stopping when it runs out of steps or if one of them requests that the build be halted. It collects status information from each one to create an overall build status (of SUCCESS, WARNINGS, or FAILURE).

All BuildSteps accept some common parameters. Some of these control how their individual status affects the overall build. Others are used to specify which Locks (see see Interlocks) should be acquired before allowing the step to run.

Arguments common to all BuildStep subclasses:

the name used to describe the step on the status display. It is also used to give a name to any LogFiles created by this step.
if True, a FAILURE of this build step will cause the build to halt immediately with an overall result of FAILURE.
when True, a WARNINGS or FAILURE of this build step will mark the overall build as FAILURE. The remaining steps will still be executed.
when True, a FAILURE of this build step will mark the overall build as a FAILURE. The remaining steps will still be executed.
when True, a WARNINGS or FAILURE of this build step will mark the overall build as having WARNINGS. The remaining steps will still be executed.
when True, a FAILURE of this build step will mark the overall build as having WARNINGS. The remaining steps will still be executed.
a list of Locks (instances of buildbot.locks.SlaveLock or buildbot.locks.MasterLock) that should be acquired before starting this Step. The Locks will be released when the step is complete. Note that this is a list of actual Lock instances, not names. Also note that all Locks must have unique names.

Next: , Previous: Common Parameters, Up: Build Steps

6.1.2 Source Checkout

The first step of any build is typically to acquire the source code from which the build will be performed. There are several classes to handle this, one for each of the different source control system that Buildbot knows about. For a description of how Buildbot treats source control in general, see Version Control Systems.

All source checkout steps accept some common parameters to control how they get the sources and where they should be placed. The remaining per-VC-system parameters are mostly to specify where exactly the sources are coming from.

a string describing the kind of VC operation that is desired. Defaults to update.
specifies that the CVS checkout/update should be performed directly into the workdir. Each build is performed in the same directory, allowing for incremental builds. This minimizes disk space, bandwidth, and CPU time. However, it may encounter problems if the build process does not handle dependencies properly (sometimes you must do a “clean build” to make sure everything gets compiled), or if source files are deleted but generated files can influence test behavior (e.g. python's .pyc files), or when source directories are deleted but generated files prevent CVS from removing them. Builds ought to be correct regardless of whether they are done “from scratch” or incrementally, but it is useful to test both kinds: this mode exercises the incremental-build style.
specifies that the CVS workspace should be maintained in a separate directory (called the 'copydir'), using checkout or update as necessary. For each build, a new workdir is created with a copy of the source tree (rm -rf workdir; cp -r copydir workdir). This doubles the disk space required, but keeps the bandwidth low (update instead of a full checkout). A full 'clean' build is performed each time. This avoids any generated-file build problems, but is still occasionally vulnerable to CVS problems such as a repository being manually rearranged, causing CVS errors on update which are not an issue with a full checkout.
specifes that the working directory should be deleted each time, necessitating a full checkout for each build. This insures a clean build off a complete checkout, avoiding any of the problems described above. This mode exercises the “from-scratch” build style.
this is like clobber, except that the 'cvs export' command is used to create the working directory. This command removes all CVS metadata files (the CVS/ directories) from the tree, which is sometimes useful for creating source tarballs (to avoid including the metadata in the tar file).

like all Steps, this indicates the directory where the build will take place. Source Steps are special in that they perform some operations outside of the workdir (like creating the workdir itself).
if True, bypass the usual “update to the last Change” behavior, and always update to the latest changes instead.
If set, this specifies a tuple of (delay, repeats) which means that when a full VC checkout fails, it should be retried up to repeats times, waiting delay seconds between attempts. If you don't provide this, it defaults to None, which means VC operations should not be retried. This is provided to make life easier for buildslaves which are stuck behind poor network connections.

My habit as a developer is to do a cvs update and make each morning. Problems can occur, either because of bad code being checked in, or by incomplete dependencies causing a partial rebuild to fail where a complete from-scratch build might succeed. A quick Builder which emulates this incremental-build behavior would use the mode='update' setting.

On the other hand, other kinds of dependency problems can cause a clean build to fail where a partial build might succeed. This frequently results from a link step that depends upon an object file that was removed from a later version of the tree: in the partial tree, the object file is still around (even though the Makefiles no longer know how to create it).

“official” builds (traceable builds performed from a known set of source revisions) are always done as clean builds, to make sure it is not influenced by any uncontrolled factors (like leftover files from a previous build). A “full” Builder which behaves this way would want to use the mode='clobber' setting.

Each VC system has a corresponding source checkout class: their arguments are described on the following pages.

Next: , Previous: Source Checkout, Up: Source Checkout CVS

The CVS build step performs a CVS checkout or update. It takes the following arguments:

(required): specify the CVSROOT value, which points to a CVS repository, probably on a remote machine. For example, the cvsroot value you would use to get a copy of the Buildbot source code is
(required): specify the cvs module, which is generally a subdirectory of the CVSROOT. The cvsmodule for the Buildbot source code is buildbot.
a string which will be used in a -r argument. This is most useful for specifying a branch to work on. Defaults to HEAD.
a list of flags to be put before the verb in the CVS command.
if set, the number of seconds to put between the timestamp of the last known Change and the value used for the -D option. Defaults to half of the parent Build's treeStableTimer.

Next: , Previous: CVS, Up: Source Checkout SVN

The SVN build step performs a Subversion checkout or update. There are two basic ways of setting up the checkout step, depending upon whether you are using multiple branches or not.

If all of your builds use the same branch, then you should create the SVN step with the svnurl argument:

(required): this specifies the URL argument that will be given to the svn checkout command. It dictates both where the repository is located and which sub-tree should be extracted. In this respect, it is like a combination of the CVS cvsroot and cvsmodule arguments. For example, if you are using a remote Subversion repository which is accessible through HTTP at a URL of, and you wanted to check out the trunk/calc sub-tree, you would use svnurl="" as an argument to your SVN step.

If, on the other hand, you are building from multiple branches, then you should create the SVN step with the baseURL and defaultBranch arguments instead:

(required): this specifies the base repository URL, to which a branch name will be appended. It should probably end in a slash.
this specifies the name of the branch to use when a Build does not provide one of its own. This will be appended to baseURL to create the string that will be passed to the svn checkout command.

If you are using branches, you must also make sure your ChangeSource will report the correct branch names.

branch example

Let's suppose that the “MyProject” repository uses branches for the trunk, for various users' individual development efforts, and for several new features that will require some amount of work (involving multiple developers) before they are ready to merge onto the trunk. Such a repository might be organized as follows:


Further assume that we want the Buildbot to run tests against the trunk and against all the feature branches (i.e., do a checkout/compile/build of branch X when a file has been changed on branch X, when X is in the set [trunk, features/newthing, features/otherthing]). We do not want the Buildbot to automatically build any of the user branches, but it should be willing to build a user branch when explicitly requested (most likely by the user who owns that branch).

There are three things that need to be set up to accomodate this system. The first is a ChangeSource that is capable of identifying the branch which owns any given file. This depends upon a user-supplied function, in an external program that runs in the SVN commit hook and connects to the buildmaster's PBChangeSource over a TCP connection. (you can use the “buildbot sendchange” utility for this purpose, but you will still need an external program to decide what value should be passed to the --branch= argument). For example, a change to a file with the SVN url of “svn://” should be broken down into a Change instance with branch='features/newthing' and file='src/foo.c'.

The second piece is an AnyBranchScheduler which will pay attention to the desired branches. It will not pay attention to the user branches, so it will not automatically start builds in response to changes there. The AnyBranchScheduler class requires you to explicitly list all the branches you want it to use, but it would not be difficult to write a subclass which used branch.startswith('features/' to remove the need for this explicit list. Or, if you want to build user branches too, you can use AnyBranchScheduler with branches=None to indicate that you want it to pay attention to all branches.

The third piece is an SVN checkout step that is configured to handle the branches correctly, with a baseURL value that matches the way the ChangeSource splits each file's URL into base, branch, and file.

     from buildbot.changes.pb import PBChangeSource
     from buildbot.scheduler import AnyBranchScheduler
     from buildbot.process import source, factory
     from buildbot.steps import source, shell
     c['sources'] = [PBChangeSource()]
     s1 = AnyBranchScheduler('main',
                             ['trunk', 'features/newthing', 'features/otherthing'],
                             10*60, ['test-i386', 'test-ppc'])
     c['schedulers'] = [s1]
     f = factory.BuildFactory()
     f.addStep(source.SVN, mode='update',
     f.addStep(shell.Compile, command="make all")
     f.addStep(shell.Test, command="make test")
     c['builders'] = [
       {'name':'test-i386', 'slavename':'bot-i386', 'builddir':'test-i386',
                            'factory':f },
       {'name':'test-ppc', 'slavename':'bot-ppc', 'builddir':'test-ppc',
                           'factory':f },

In this example, when a change arrives with a branch attribute of “trunk”, the resulting build will have an SVN step that concatenates “svn://” (the baseURL) with “trunk” (the branch name) to get the correct svn command. If the “newthing” branch has a change to “src/foo.c”, then the SVN step will concatenate “svn://” with “features/newthing” to get the svnurl for checkout.

Next: , Previous: SVN, Up: Source Checkout Darcs

The Darcs build step performs a Darcs checkout or update.

Like See SVN, this step can either be configured to always check out a specific tree, or set up to pull from a particular branch that gets specified separately for each build. Also like SVN, the repository URL given to Darcs is created by concatenating a baseURL with the branch name, and if no particular branch is requested, it uses a defaultBranch. The only difference in usage is that each potential Darcs repository URL must point to a fully-fledged repository, whereas SVN URLs usually point to sub-trees of the main Subversion repository. In other words, doing an SVN checkout of baseURL is legal, but silly, since you'd probably wind up with a copy of every single branch in the whole repository. Doing a Darcs checkout of baseURL is just plain wrong, since the parent directory of a collection of Darcs repositories is not itself a valid repository.

The Darcs step takes the following arguments:

(required unless baseURL is provided): the URL at which the Darcs source repository is available.
(required unless repourl is provided): the base repository URL, to which a branch name will be appended. It should probably end in a slash.
(allowed if and only if baseURL is provided): this specifies the name of the branch to use when a Build does not provide one of its own. This will be appended to baseURL to create the string that will be passed to the darcs get command.

Next: , Previous: Darcs, Up: Source Checkout Mercurial

The Mercurial build step performs a Mercurial (aka “hg”) checkout or update.

Branches are handled just like See Darcs.

The Mercurial step takes the following arguments:

(required unless baseURL is provided): the URL at which the Mercurial source repository is available.
(required unless repourl is provided): the base repository URL, to which a branch name will be appended. It should probably end in a slash.
(allowed if and only if baseURL is provided): this specifies the name of the branch to use when a Build does not provide one of its own. This will be appended to baseURL to create the string that will be passed to the hg clone command.

Next: , Previous: Mercurial, Up: Source Checkout Arch

The Arch build step performs an Arch checkout or update using the tla client. It takes the following arguments:

(required): this specifies the URL at which the Arch source archive is available.
(required): this specifies which “development line” (like a branch) should be used. This provides the default branch name, but individual builds may specify a different one.
(optional): Each repository knows its own archive name. If this parameter is provided, it must match the repository's archive name. The parameter is accepted for compatibility with the Bazaar step, below.

Next: , Previous: Arch, Up: Source Checkout Bazaar

Bazaar is an alternate implementation of the Arch VC system, which uses a client named baz. The checkout semantics are just different enough from tla that there is a separate BuildStep for it.

It takes exactly the same arguments as Arch, except that the archive= parameter is required. (baz does not emit the archive name when you do baz register-archive, so we must provide it ourselves).

Previous: Bazaar, Up: Source Checkout P4

The P4 build step creates a Perforce client specification and performs an update.

A view into the Perforce depot without branch name or trailing "...". Typically "//depot/proj/".
A branch name to append on build requests if none is specified. Typically "trunk".
(optional): the host:port string describing how to get to the P4 Depot (repository), used as the -p argument for all p4 commands.
(optional): the Perforce user, used as the -u argument to all p4 commands.
(optional): the Perforce password, used as the -p argument to all p4 commands.
(optional): a list of (depotpath, clientpath) tuples containing extra views to be mapped into the client specification. Both will have "/..." appended automatically. The client name and source directory will be prepended to the client path.
(optional): The name of the client to use. In mode='copy' and mode='update', it's particularly important that a unique name is used for each checkout directory to avoid incorrect synchronization. For this reason, Python percent substitution will be performed on this value to replace %(slave)s with the slave name and %(builder)s with the builder name. The default is "buildbot_%(slave)s_%(build)s".

Next: , Previous: Source Checkout, Up: Build Steps

6.1.3 ShellCommand

This is a useful base class for just about everything you might want to do during a build (except for the initial source checkout). It runs a single command in a child shell on the buildslave. All stdout/stderr is recorded into a LogFile. The step finishes with a status of FAILURE if the command's exit code is non-zero, otherwise it has a status of SUCCESS.

The preferred way to specify the command is with a list of argv strings, since this allows for spaces in filenames and avoids doing any fragile shell-escaping. You can also specify the command with a single string, in which case the string is given to '/bin/sh -c COMMAND' for parsing.

All ShellCommands are run by default in the “workdir”, which defaults to the “build” subdirectory of the slave builder's base directory. The absolute path of the workdir will thus be the slave's basedir (set as an option to buildbot create-slave, see Creating a buildslave) plus the builder's basedir (set in the builder's c['builddir'] key in master.cfg) plus the workdir itself (a class-level attribute of the BuildFactory, defaults to “build”).

ShellCommand arguments:

a list of strings (preferred) or single string (discouraged) which specifies the command to be run. A list of strings is preferred because it can be used directly as an argv array. Using a single string (with embedded spaces) requires the buildslave to pass the string to /bin/sh for interpretation, which raises all sorts of difficult questions about how to escape or interpret shell metacharacters.
a dictionary of environment strings which will be added to the child command's environment. For example, to run tests with a different i18n language setting, you might use
          f.addStep(ShellCommand, command=["make", "test"],
                    env={'LANG': 'fr_FR'})

These variable settings will override any existing ones in the buildslave's environment. The exception is PYTHONPATH, which is merged with (actually prepended to) any existing $PYTHONPATH setting. The value is treated as a list of directories to prepend, and a single string is treated like a one-item list. For example, to prepend both /usr/local/lib/python2.3 and /home/buildbot/lib/python to any existing $PYTHONPATH setting, you would do something like the following:

          f.addStep(ShellCommand, command=["make", "test"],
                    env={'PYTHONPATH': ["/usr/local/lib/python2.3",
                                        "/home/buildbot/lib/python"] })

if False, stdout from the child process is discarded rather than being sent to the buildmaster for inclusion in the step's LogFile.
like want_stdout but for stderr. Note that commands run through a PTY do not have separate stdout/stderr streams: both are merged into stdout.
Sometimes commands will log interesting data to a local file, rather than emitting everything to stdout or stderr. For example, Twisted's “trial” command (which runs unit tests) only presents summary information to stdout, and puts the rest into a file named _trial_temp/test.log. It is often useful to watch these files as the command runs, rather than using /bin/cat to dump their contents afterwards.

The logfiles= argument allows you to collect data from these secondary logfiles in near-real-time, as the step is running. It accepts a dictionary which maps from a local Log name (which is how the log data is presented in the build results) to a remote filename (interpreted relative to the build's working directory). Each named file will be polled on a regular basis (every couple of seconds) as the build runs, and any new text will be sent over to the buildmaster.

          f.addStep(ShellCommand, command=["make", "test"],
                    logfiles={"triallog": "_trial_temp/test.log"})

if the command fails to produce any output for this many seconds, it is assumed to be locked up and will be killed.
This will be used to describe the command (on the Waterfall display) while the command is still running. It should be a single imperfect-tense verb, like “compiling” or “testing”. The preferred form is a list of short strings, which allows the HTML Waterfall display to create narrower columns by emitting a <br> tag between each word. You may also provide a single string.
This will be used to describe the command once it has finished. A simple noun like “compile” or “tests” should be used. Like description, this may either be a list of short strings or a single string.

If neither description nor descriptionDone are set, the actual command arguments will be used to construct the description. This may be a bit too wide to fit comfortably on the Waterfall display.

          f.addStep(ShellCommand, command=["make", "test"],

Next: , Previous: ShellCommand, Up: Build Steps

6.1.4 Simple ShellCommand Subclasses

Several subclasses of ShellCommand are provided as starting points for common build steps. These are all very simple: they just override a few parameters so you don't have to specify them yourself, making the master.cfg file less verbose.

Next: , Previous: Simple ShellCommand Subclasses, Up: Simple ShellCommand Subclasses Configure

This is intended to handle the ./configure step from autoconf-style projects, or the perl Makefile.PL step from perl modules. The default command is ./configure but you can change this by providing a command= parameter.

Next: , Previous: Configure, Up: Simple ShellCommand Subclasses Compile

This is meant to handle compiling or building a project written in C. The default command is make all. When the compile is finished, the log file is scanned for GCC error/warning messages and a summary log is created with any problems that were seen (TODO: the summary is not yet created).

Next: , Previous: Compile, Up: Simple ShellCommand Subclasses Test

This is meant to handle unit tests. The default command is make test, and the warnOnFailure flag is set.

Previous: Test, Up: Simple ShellCommand Subclasses Build Properties

Each build has a set of “Build Properties”, which can be used by its BuildStep to modify their actions. For example, the SVN revision number of the source code being built is available as a build property, and a ShellCommand step could incorporate this number into a command which create a numbered release tarball.

Some build properties are set when the build starts, such as the SourceStamp information. Other properties can be set by BuildSteps as they run, for example the various Source steps will set the got_revision property to the source revision that was actually checked out (which can be useful when the SourceStamp in use merely requested the “latest revision”: got_revision will tell you what was actually built).

In custom BuildSteps, you can get and set the build properties with the getProperty/setProperty methods. Each takes a string for the name of the property, and returns or accepts an arbitrary7 object. For example:

     class MakeTarball(ShellCommand):
         def start(self):
             self.setCommand(["tar", "czf",
                              "build-%s.tar.gz" % self.getProperty("revision"),

You can use build properties in ShellCommands by using the WithProperties wrapper when setting the arguments of the ShellCommand. This interpolates the named build properties into the generated shell command.

     from import ShellCommand, WithProperties
               command=["tar", "czf",
                        WithProperties("build-%s.tar.gz", "revision"),

If this BuildStep were used in a tree obtained from Subversion, it would create a tarball with a name like build-1234.tar.gz.

The WithProperties function does printf-style string interpolation, using strings obtained by calling build.getProperty(propname). Note that for every %s (or %d, etc), you must have exactly one additional argument to indicate which build property you want to insert.

You can also use python dictionary-style string interpolation by using the %(propname)s syntax. In this form, the property name goes in the parentheses, and WithProperties takes no additional arguments:

               command=["tar", "czf",

Don't forget the extra “s” after the closing parenthesis! This is the cause of many confusing errors. Also note that you can only use WithProperties in the list form of the command= definition. You cannot currently use it in the (discouraged) command="stuff" single-string form. However, you can use something like command=["/bin/sh", "-c", "stuff", WithProperties(stuff)] to use both shell expansion and WithProperties interpolation.

Note that, like python, you can either do positional-argument interpolation or keyword-argument interpolation, not both. Thus you cannot use a string like WithProperties("foo-%(revision)s-%s", "branch").

At the moment, the only way to set build properties is by writing a custom BuildStep.

Common Build Properties

The following build properties are set when the build is started, and are available to all steps.

This comes from the build's SourceStamp, and describes which branch is being checked out. This will be None (which interpolates into WithProperties as an empty string) if the build is on the default branch, which is generally the trunk. Otherwise it will be a string like “branches/beta1.4”. The exact syntax depends upon the VC system being used.
This also comes from the SourceStamp, and is the revision of the source code tree that was requested from the VC system. When a build is requested of a specific revision (as is generally the case when the build is triggered by Changes), this will contain the revision specification. The syntax depends upon the VC system in use: for SVN it is an integer, for Mercurial it is a short string, for Darcs it is a rather large string, etc.

If the “force build” button was pressed, the revision will be None, which means to use the most recent revision available. This is a “trunk build”. This will be interpolated as an empty string.

This is set when a Source step checks out the source tree, and provides the revision that was actually obtained from the VC system. In general this should be the same as revision, except for trunk builds, where got_revision indicates what revision was current when the checkout was performed. This can be used to rebuild the same source code later.

Note that for some VC systems (Darcs in particular), the revision is a large string containing newlines, and is not suitable for interpolation into a filename.

This is a string that indicates which Builder the build was a part of. The combination of buildername and buildnumber uniquely identify a build.
Each build gets a number, scoped to the Builder (so the first build performed on any given Builder will have a build number of 0). This integer property contains the build's number.
This is a string which identifies which buildslave the build is running on.

Next: , Previous: Simple ShellCommand Subclasses, Up: Build Steps

6.1.5 Python BuildSteps

Here are some BuildSteps that are specifcally useful for projects implemented in Python.

Next: , Previous: Python BuildSteps, Up: Python BuildSteps BuildEPYDoc

epydoc is a tool for generating API documentation for Python modules from their docstrings. It reads all the .py files from your source tree, processes the docstrings therein, and creates a large tree of .html files (or a single .pdf file).

The buildbot.steps.python.BuildEPYDoc step will run epydoc to produce this API documentation, and will count the errors and warnings from its output.

You must supply the command line to be used. The default is make epydocs, which assumes that your project has a Makefile with an “epydocs” target. You might wish to use something like epydoc -o apiref source/PKGNAME instead. You might also want to add --pdf to generate a PDF file instead of a large tree of HTML files.

The API docs are generated in-place in the build tree (under the workdir, in the subdirectory controlled by the “-o” argument). To make them useful, you will probably have to copy them to somewhere they can be read. A command like rsync -ad apiref/ might be useful. You might instead want to bundle them into a tarball and publish it in the same place where the generated install tarball is placed.

     from buildbot.steps.python import BuildEPYDoc
     f.addStep(BuildEPYDoc, command=["epydoc", "-o", "apiref", "source/mypkg"])

Previous: BuildEPYDoc, Up: Python BuildSteps PyFlakes

PyFlakes is a tool to perform basic static analysis of Python code to look for simple errors, like missing imports and references of undefined names. It is like a fast and simple form of the C “lint” program. Other tools (like pychecker) provide more detailed results but take longer to run.

The buildbot.steps.python.PyFlakes step will run pyflakes and count the various kinds of errors and warnings it detects.

You must supply the command line to be used. The default is make pyflakes, which assumes you have a top-level Makefile with a “pyflakes” target. You might want to use something like pyflakes . or pyflakes src.

     from buildbot.steps.python import PyFlakes
     f.addStep(PyFlakes, command=["pyflakes", "src"])

Next: , Previous: Python BuildSteps, Up: Build Steps

6.1.6 Transferring Files

Most of the work involved in a build will take place on the buildslave. But occasionally it is useful to do some work on the buildmaster side. The most basic way to involve the buildmaster is simply to move a file from the slave to the master, or vice versa. There are a pair of BuildSteps named FileUpload and FileDownload to provide this functionality. FileUpload moves a file up to the master, while FileDownload moves a file down from the master.

As an example, let's assume that there is a step which produces an HTML file within the source tree that contains some sort of generated project documentation. We want to move this file to the buildmaster, into a ~/public_html directory, so it can be visible to developers. This file will wind up in the slave-side working directory under the name docs/reference.html. We want to put it into the master-side ~/public_html/ref.html.

     from import ShellCommand
     from buildbot.steps.transfer import FileUpload
     f.addStep(ShellCommand, command=["make", "docs"])

The masterdest= argument will be passed to os.path.expanduser, so things like “~” will be expanded properly. Non-absolute paths will be interpreted relative to the buildmaster's base directory. Likewise, the slavesrc= argument will be expanded and interpreted relative to the builder's working directory.

To move a file from the master to the slave, use the FileDownload command. For example, let's assume that some step requires a configuration file that, for whatever reason, could not be recorded in the source code repository or generated on the buildslave side:

     from import ShellCommand
     from buildbot.steps.transfer import FileUpload
     f.addStep(ShellCommand, command=["make", "config"])

Like FileUpload, the mastersrc= argument is interpreted relative to the buildmaster's base directory, and the slavedest= argument is relative to the builder's working directory. If the buildslave is running in ~buildslave, and the builder's “builddir” is something like tests-i386, then the workdir is going to be ~buildslave/tests-i386/build, and a slavedest= of foo/bar.html will get put in ~buildslave/tests-i386/build/foo/bar.html. Remember that neither of these commands will create missing directories for you.

Other Parameters

The maxsize= argument lets you set a maximum size for the file to be transferred. This may help to avoid surprises: transferring a 100MB coredump when you were expecting to move a 10kB status file might take an awfully long time. The blocksize= argument controls how the file is sent over the network: larger blocksizes are slightly more efficient but also consume more memory on each end, and there is a hard-coded limit of about 640kB.

The mode= argument allows you to control the access permissions of the target file, traditionally expressed as an octal integer. The most common value is probably 0755, which sets the “x” executable bit on the file (useful for shell scripts and the like). The default value for mode= is None, which means the permission bits will default to whatever the umask of the writing process is. The default umask tends to be fairly restrictive, but at least on the buildslave you can make it less restrictive with a –umask command-line option at creation time (see Buildslave Options).

Previous: Transferring Files, Up: Build Steps

6.1.7 Writing New BuildSteps

While it is a good idea to keep your build process self-contained in the source code tree, sometimes it is convenient to put more intelligence into your Buildbot configuration. One was to do this is to write a custom BuildStep. Once written, this Step can be used in the master.cfg file.

The best reason for writing a custom BuildStep is to better parse the results of the command being run. For example, a BuildStep that knows about JUnit could look at the logfiles to determine which tests had been run, how many passed and how many failed, and then report more detailed information than a simple rc==0 -based “good/bad” decision.

TODO: add more description of BuildSteps.

Next: , Previous: Writing New BuildSteps, Up: Writing New BuildSteps BuildStep LogFiles

Each BuildStep has a collection of “logfiles”. Each one has a short name, like “stdio” or “warnings”. Each LogFile contains an arbitrary amount of text, usually the contents of some output file generated during a build or test step, or a record of everything that was printed to stdout/stderr during the execution of some command.

These LogFiles are stored to disk, so they can be retrieved later.

Each can contain multiple “channels”, generally limited to three basic ones: stdout, stderr, and “headers”. For example, when a ShellCommand runs, it writes a few lines to the “headers” channel to indicate the exact argv strings being run, which directory the command is being executed in, and the contents of the current environment variables. Then, as the command runs, it adds a lot of “stdout” and “stderr” messages. When the command finishes, a final “header” line is added with the exit code of the process.

Status display plugins can format these different channels in different ways. For example, the web page shows LogFiles as text/html, with header lines in blue text, stdout in black, and stderr in red. A different URL is available which provides a text/plain format, in which stdout and stderr are collapsed together, and header lines are stripped completely. This latter option makes it easy to save the results to a file and run grep or whatever against the output.

Each BuildStep contains a mapping (implemented in a python dictionary) from LogFile name to the actual LogFile objects. Status plugins can get a list of LogFiles to display, for example, a list of HREF links that, when clicked, provide the full contents of the LogFile.

Using LogFiles in custom BuildSteps

The most common way for a custom BuildStep to use a LogFile is to summarize the results of a ShellCommand (after the command has finished running). For example, a compile step with thousands of lines of output might want to create a summary of just the warning messages. If you were doing this from a shell, you would use something like:

     grep "warning:" output.log >warnings.log

In a custom BuildStep, you could instead create a “warnings” LogFile that contained the same text. To do this, you would add code to your createSummary method that pulls lines from the main output log and creates a new LogFile with the results:

         def createSummary(self, log):
             warnings = []
             for line in log.readlines():
                 if "warning:" in line:
             self.addCompleteLog('warnings', "".join(warnings))

This example uses the addCompleteLog method, which creates a new LogFile, puts some text in it, and then “closes” it, meaning that no further contents will be added. This LogFile will appear in the HTML display under an HREF with the name “warnings”, since that is the name of the LogFile.

You can also use addHTMLLog to create a complete (closed) LogFile that contains HTML instead of plain text. The normal LogFile will be HTML-escaped if presented through a web page, but the HTML LogFile will not. At the moment this is only used to present a pretty HTML representation of an otherwise ugly exception traceback when something goes badly wrong during the BuildStep.

In contrast, you might want to create a new LogFile at the beginning of the step, and add text to it as the command runs. You can create the LogFile and attach it to the build by calling addLog, which returns the LogFile object. You then add text to this LogFile by calling methods like addStdout and addHeader. When you are done, you must call the finish method so the LogFile can be closed. It may be useful to create and populate a LogFile like this from a LogObserver method See Adding LogObservers.

The logfiles= argument to ShellCommand (see see ShellCommand) creates new LogFiles and fills them in realtime by asking the buildslave to watch a actual file on disk. The buildslave will look for additions in the target file and report them back to the BuildStep. These additions will be added to the LogFile by calling addStdout. These secondary LogFiles can be used as the source of a LogObserver just like the normal “stdio” LogFile.

Next: , Previous: BuildStep LogFiles, Up: Writing New BuildSteps Adding LogObservers

Most shell commands emit messages to stdout or stderr as they operate, especially if you ask them nicely with a --verbose flag of some sort. They may also write text to a log file while they run. Your BuildStep can watch this output as it arrives, to keep track of how much progress the command has made. You can get a better measure of progress by counting the number of source files compiled or test cases run than by merely tracking the number of bytes that have been written to stdout. This improves the accuracy and the smoothness of the ETA display.

To accomplish this, you will need to attach a LogObserver to one of the log channels, most commonly to the “stdio” channel but perhaps to another one which tracks a log file. This observer is given all text as it is emitted from the command, and has the opportunity to parse that output incrementally. Once the observer has decided that some event has occurred (like a source file being compiled), it can use the setProgress method to tell the BuildStep about the progress that this event represents.

There are a number of pre-built LogObserver classes that you can choose from (defined in buildbot.process.buildstep, and of course you can subclass them to add further customization. The LogLineObserver class handles the grunt work of buffering and scanning for end-of-line delimiters, allowing your parser to operate on complete stdout/stderr lines.

For example, let's take a look at the TrialTestCaseCounter, which is used by the Trial step to count test cases as they are run. As Trial executes, it emits lines like the following:

     buildbot.test.test_config.ConfigTest.testDebugPassword ... [OK]
     buildbot.test.test_config.ConfigTest.testEmpty ... [OK]
     buildbot.test.test_config.ConfigTest.testIRC ... [FAIL]
     buildbot.test.test_config.ConfigTest.testLocks ... [OK]

When the tests are finished, trial emits a long line of “======” and then some lines which summarize the tests that failed. We want to avoid parsing these trailing lines, because their format is less well-defined than the “[OK]” lines.

The parser class looks like this:

     from buildbot.process.buildstep import LogLineObserver
     class TrialTestCaseCounter(LogLineObserver):
         _line_re = re.compile(r'^([\w\.]+) \.\.\. \[([^\]]+)\]$')
         numTests = 0
         finished = False
         def outLineReceived(self, line):
             if self.finished:
             if line.startswith("=" * 40):
                 self.finished = True
             m =
             if m:
                 testname, result = m.groups()
                 self.numTests += 1
                 self.step.setProgress('tests', self.numTests)

This parser only pays attention to stdout, since that's where trial writes the progress lines. It has a mode flag named finished to ignore everything after the “====” marker, and a scary-looking regular expression to match each line while hopefully ignoring other messages that might get displayed as the test runs.

Each time it identifies a test has been completed, it increments its counter and delivers the new progress value to the step with self.step.setProgress. This class is specifically measuring progress along the “tests” metric, in units of test cases (as opposed to other kinds of progress like the “output” metric, which measures in units of bytes). The Progress-tracking code uses each progress metric separately to come up with an overall completion percentage and an ETA value.

To connect this parser into the Trial BuildStep, Trial.__init__ ends with the following clause:

             # this counter will feed Progress along the 'test cases' metric
             counter = TrialTestCaseCounter()
             self.addLogObserver('stdio', counter)

This creates a TrialTestCaseCounter and tells the step that the counter wants to watch the “stdio” log. The observer is automatically given a reference to the step in its .step attribute.

A Somewhat Whimsical Example

Let's say that we've got some snazzy new unit-test framework called Framboozle. It's the hottest thing since sliced bread. It slices, it dices, it runs unit tests like there's no tomorrow. Plus if your unit tests fail, you can use its name for a Web 2.1 startup company, make millions of dollars, and hire engineers to fix the bugs for you, while you spend your afternoons lazily hang-gliding along a scenic pacific beach, blissfully unconcerned about the state of your tests.8

To run a Framboozle-enabled test suite, you just run the 'framboozler' command from the top of your source code tree. The 'framboozler' command emits a bunch of stuff to stdout, but the most interesting bit is that it emits the line "FNURRRGH!" every time it finishes running a test case9. You'd like to have a test-case counting LogObserver that watches for these lines and counts them, because counting them will help the buildbot more accurately calculate how long the build will take, and this will let you know exactly how long you can sneak out of the office for your hang-gliding lessons without anyone noticing that you're gone.

This will involve writing a new BuildStep (probably named "Framboozle") which inherits from ShellCommand. The BuildStep class definition itself will look something like this:

     # START
     from import ShellCommand
     from buildbot.process.buildstep import LogLineObserver
     class FNURRRGHCounter(LogLineObserver):
         numTests = 0
         def outLineReceived(self, line):
             if "FNURRRGH!" in line:
                 self.numTests += 1
                 self.step.setProgress('tests', self.numTests)
     class Framboozle(ShellCommand):
         command = ["framboozler"]
         def __init__(self, **kwargs):
             ShellCommand.__init__(self, **kwargs)   # always upcall!
             counter = FNURRRGHCounter())
     # FINISH

So that's the code that we want to wind up using. How do we actually deploy it?

You have a couple of different options.

Option 1: The simplest technique is to simply put this text (everything from START to FINISH) in your master.cfg file, somewhere before the BuildFactory definition where you actually use it in a clause like:

     f = BuildFactory()
     f.addStep(SVN, svnurl="stuff")

Remember that master.cfg is secretly just a python program with one job: populating the BuildmasterConfig dictionary. And python programs are allowed to define as many classes as they like. So you can define classes and use them in the same file, just as long as the class is defined before some other code tries to use it.

This is easy, and it keeps the point of definition very close to the point of use, and whoever replaces you after that unfortunate hang-gliding accident will appreciate being able to easily figure out what the heck this stupid "Framboozle" step is doing anyways. The downside is that every time you reload the config file, the Framboozle class will get redefined, which means that the buildmaster will think that you've reconfigured all the Builders that use it, even though nothing changed. Bleh.

Option 2: Instead, we can put this code in a separate file, and import it into the master.cfg file just like we would the normal buildsteps like ShellCommand and SVN.

Create a directory named ~/lib/python, put everything from START to FINISH in ~/lib/python/, and run your buildmaster using:

      PYTHONPATH=~/lib/python buildbot start MASTERDIR

or use the Makefile.buildbot to control the way buildbot start works. Or add something like this to something like your ~/.bashrc or ~/.bash_profile or ~/.cshrc:

      export PYTHONPATH=~/lib/python

Once we've done this, our master.cfg can look like:

     from framboozle import Framboozle
     f = BuildFactory()
     f.addStep(SVN, svnurl="stuff")


     import framboozle
     f = BuildFactory()
     f.addStep(SVN, svnurl="stuff")

(check out the python docs for details about how "import" and "from A import B" work).

What we've done here is to tell python that every time it handles an "import" statement for some named module, it should look in our ~/lib/python/ for that module before it looks anywhere else. After our directories, it will try in a bunch of standard directories too (including the one where buildbot is installed). By setting the PYTHONPATH environment variable, you can add directories to the front of this search list.

Python knows that once it "import"s a file, it doesn't need to re-import it again. This means that reconfiguring the buildmaster (with "buildbot reconfig", for example) won't make it think the Framboozle class has changed every time, so the Builders that use it will not be spuriously restarted. On the other hand, you either have to start your buildmaster in a slightly weird way, or you have to modify your environment to set the PYTHONPATH variable.

Option 3: Install this code into a standard python library directory

Find out what your python's standard include path is by asking it:

     80:warner@luther% python
     Python 2.4.4c0 (#2, Oct  2 2006, 00:57:46)
     [GCC 4.1.2 20060928 (prerelease) (Debian 4.1.1-15)] on linux2
     Type "help", "copyright", "credits" or "license" for more information.
     >>> import sys
     >>> print sys.path
     ['', '/usr/lib/', '/usr/lib/python2.4', '/usr/lib/python2.4/plat-linux2', '/usr/lib/python2.4/lib-tk', '/usr/lib/python2.4/lib-dynload', '/usr/local/lib/python2.4/site-packages', '/usr/lib/python2.4/site-packages', '/usr/lib/python2.4/site-packages/Numeric', '/var/lib/python-support/python2.4', '/usr/lib/site-python']

In this case, putting the code into /usr/local/lib/python2.4/site-packages/ would work just fine. We can use the same master.cfg "import framboozle" statement as in Option 2. By putting it in a standard include directory (instead of the decidedly non-standard ~/lib/python), we don't even have to set PYTHONPATH to anything special. The downside is that you probably have to be root to write to one of those standard include directories.

Option 4: Submit the code for inclusion in the Buildbot distribution

Contribute the code in an Enhancement Request on SourceForge, via . Lobby, convince, coerce, bribe, badger, harass, threaten, or otherwise encourage the author to accept the patch. This lets you do something like:

     from buildbot.steps import framboozle
     f = BuildFactory()
     f.addStep(SVN, svnurl="stuff")

And then you don't even have to install anywhere on your system, since it will ship with Buildbot. You don't have to be root, you don't have to set PYTHONPATH. But you do have to make a good case for Framboozle being worth going into the main distribution, you'll probably have to provide docs and some unit test cases, you'll need to figure out what kind of beer the author likes, and then you'll have to wait until the next release. But in some environments, all this is easier than getting root on your buildmaster box, so the tradeoffs may actually be worth it.

Putting the code in master.cfg (1) makes it available to that buildmaster instance. Putting it in a file in a personal library directory (2) makes it available for any buildmasters you might be running. Putting it in a file in a system-wide shared library directory (3) makes it available for any buildmasters that anyone on that system might be running. Getting it into the buildbot's upstream repository (4) makes it available for any buildmasters that anyone in the world might be running. It's all a matter of how widely you want to deploy that new class.

Previous: Adding LogObservers, Up: Writing New BuildSteps BuildStep URLs

Each BuildStep has a collection of “links”. Like its collection of LogFiles, each link has a name and a target URL. The web status page creates HREFs for each link in the same box as it does for LogFiles, except that the target of the link is the external URL instead of an internal link to a page that shows the contents of the LogFile.

These external links can be used to point at build information hosted on other servers. For example, the test process might produce an intricate description of which tests passed and failed, or some sort of code coverage data in HTML form, or a PNG or GIF image with a graph of memory usage over time. The external link can provide an easy way for users to navigate from the buildbot's status page to these external web sites or file servers. Note that the step itself is responsible for insuring that there will be a document available at the given URL (perhaps by using scp to copy the HTML output to a ~/public_html/ directory on a remote web server). Calling addURL does not magically populate a web server.

To set one of these links, the BuildStep should call the addURL method with the name of the link and the target URL. Multiple URLs can be set.

In this example, we assume that the make test command causes a collection of HTML files to be created and put somewhere on the web server, in a filename that incorporates the build number.

     class TestWithCodeCoverage(BuildStep):
         command = ["make", "test",
                    WithProperties("buildnum=%s" % "buildnumber")]
         def createSummary(self, log):
             buildnumber = self.getProperty("buildnumber")
             url = "" % buildnumber
             self.addURL("coverage", url)

You might also want to extract the URL from some special message output by the build process itself:

     class TestWithCodeCoverage(BuildStep):
         command = ["make", "test",
                    WithProperties("buildnum=%s" % "buildnumber")]
         def createSummary(self, log):
             output = StringIO(log.getText())
             for line in output.readlines():
                 if line.startswith("coverage-url:"):
                     url = line[len("coverage-url:"):].strip()
                     self.addURL("coverage", url)

Note that a build process which emits both stdout and stderr might cause this line to be split or interleaved between other lines. It might be necessary to restrict the getText() call to only stdout with something like this:

             output = StringIO("".join([c[1]
                                        for c in log.getChunks()
                                        if c[0] == LOG_CHANNEL_STDOUT]))

Of course if the build is run under a PTY, then stdout and stderr will be merged before the buildbot ever sees them, so such interleaving will be unavoidable.

Next: , Previous: Build Steps, Up: Build Process

6.2 Interlocks

For various reasons, you may want to prevent certain Steps (or perhaps entire Builds) from running simultaneously. Limited CPU speed or network bandwidth to the VC server, problems with simultaneous access to a database server used by unit tests, or multiple Builds which access shared state may all require some kind of interlock to prevent corruption, confusion, or resource overload. These resources might require completely exclusive access, or it might be sufficient to establish a limit of two or three simultaneous builds.

Locks are the mechanism used to express these kinds of constraints on when Builds or Steps can be run. There are two kinds of Locks, each with their own scope: MasterLock instances are scoped to the buildbot as a whole, while SlaveLocks are scoped to a single buildslave. This means that each buildslave has a separate copy of each SlaveLock, which could enforce a one-Build-at-a-time limit for each machine, but still allow as many simultaneous builds as there are machines.

Each Lock is created with a unique name. Each lock gets a count of how many owners it may have: how many processes can claim it at ths same time. This limit defaults to one, and is controllable through the maxCount argument. On SlaveLocks you can set the owner count on a per-slave basis by providing a dictionary (that maps from slavename to maximum owner count) to its maxCountForSlave argument. Any buildslaves that aren't mentioned in maxCountForSlave get their owner count from maxCount.

To use a lock, simply include it in the locks= argument of the BuildStep object that should obtain the lock before it runs. This argument accepts a list of Lock objects: the Step will acquire all of them before it runs.

To claim a lock for the whole Build, add a 'locks' key to the builder specification dictionary with the same list of Lock objects. (This is the dictionary that has the 'name', 'slavename', 'builddir', and 'factory' keys). The Build object also accepts a locks= argument, but unless you are writing your own BuildFactory subclass then it will be easier to set the locks in the builder dictionary.

Note that there are no partial-acquire or partial-release semantics: this prevents deadlocks caused by two Steps each waiting for a lock held by the other10. This also means that waiting to acquire a Lock can take an arbitrarily long time: if the buildmaster is very busy, a Step or Build which requires only one Lock may starve another that is waiting for that Lock plus some others.

In the following example, we run the same build on three different platforms. The unit-test steps of these builds all use a common database server, and would interfere with each other if allowed to run simultaneously. The Lock prevents more than one of these builds from happening at the same time.

     from buildbot import locks
     from buildbot.steps import source, shell
     from buildbot.process import factory
     db_lock = locks.MasterLock("database")
     f = factory.BuildFactory()
     f.addStep(source.SVN, svnurl="")
     f.addStep(shell.ShellCommand, command="make all")
     f.addStep(shell.ShellCommand, command="make test", locks=[db_lock])
     b1 = {'name': 'full1', 'slavename': 'bot-1', builddir='f1', 'factory': f}
     b2 = {'name': 'full2', 'slavename': 'bot-2', builddir='f2', 'factory': f}
     b3 = {'name': 'full3', 'slavename': 'bot-3', builddir='f3', 'factory': f}
     c['builders'] = [b1, b2, b3]

In the next example, we have one buildslave hosting three separate Builders (each running tests against a different version of Python). The machine which hosts this buildslave is not particularly fast, so we want to prevent all three builds from all happening at the same time. (Assume we've experimentally determined that one build leaves unused CPU capacity, three builds causes a lot of disk thrashing, but two builds at a time is Just Right). We use a SlaveLock because the builds happening on this one slow slave should not affect builds running on other slaves, and we use the lock on the build as a whole because the slave is so slow that even multiple simultaneous SVN checkouts would be too taxing. We set maxCount=2 to achieve our goal of two simultaneous builds per slave.

     from buildbot import locks
     from buildbot.steps import source
     from buildbot.process import s, factory
     slow_lock = locks.SlaveLock("cpu", maxCount=2)
     source = s(source.SVN, svnurl="")
     f22 = factory.Trial(source, trialpython=["python2.2"])
     f23 = factory.Trial(source, trialpython=["python2.3"])
     f24 = factory.Trial(source, trialpython=["python2.4"])
     b1 = {'name': 'p22', 'slavename': 'bot-1', builddir='p22', 'factory': f22,
           'locks': [slow_lock] }
     b2 = {'name': 'p23', 'slavename': 'bot-1', builddir='p23', 'factory': f23,
           'locks': [slow_lock] }
     b3 = {'name': 'p24', 'slavename': 'bot-1', builddir='p24', 'factory': f24,
           'locks': [slow_lock] }
     c['builders'] = [b1, b2, b3]

In the last example, we use two Locks at the same time. In this case, we're concerned about both of the previous constraints, but we'll say that only the tests are computationally intensive, and that they have been split into those which use the database and those which do not. In addition, two of the Builds run on a fast machine which does not need to worry about the cpu lock, but which still must be prevented from simultaneous database access. We use maxCountForSlave to limit the slow machine to one simultanous build, but allow practically unlimited concurrent builds on the fast machine.

     from buildbot import locks
     from buildbot.steps import source, shell
     from buildbot.process import factory
     db_lock = locks.MasterLock("database")
     slavecounts = {"bot-slow": 1, "bot-fast": 100}
     cpu_lock = locks.SlaveLock("cpu", maxCountForSlave=slavecounts)
     f = factory.BuildFactory()
     f.addStep(source.SVN, svnurl="")
     f.addStep(shell.ShellCommand, command="make all", locks=[cpu_lock])
     f.addStep(shell.ShellCommand, command="make test", locks=[cpu_lock])
     f.addStep(shell.ShellCommand, command="make db-test",
                                   locks=[db_lock, cpu_lock])
     b1 = {'name': 'full1', 'slavename': 'bot-slow', builddir='full1',
           'factory': f}
     b2 = {'name': 'full2', 'slavename': 'bot-slow', builddir='full2',
           'factory': f}
     b3 = {'name': 'full3', 'slavename': 'bot-fast', builddir='full3',
           'factory': f}
     b4 = {'name': 'full4', 'slavename': 'bot-fast', builddir='full4',
           'factory': f}
     c['builders'] = [b1, b2, b3, b4]

As a final note, remember that a unit test system which breaks when multiple people run it at the same time is fragile and should be fixed. Asking your human developers to serialize themselves when running unit tests will just discourage them from running the unit tests at all. Find a way to fix this: change the database tests to create a new (uniquely-named) user or table for each test run, don't use fixed listening TCP ports for network tests (instead listen on port 0 to let the kernel choose a port for you and then query the socket to find out what port was allocated). MasterLocks can be used to accomodate broken test systems like this, but are really intended for other purposes: build processes that store or retrieve products in shared directories, or which do things that human developers would not (or which might slow down or break in ways that require human attention to deal with).

SlaveLockss can be used to keep automated performance tests from interfering with each other, when there are multiple Builders all using the same buildslave. But they can't prevent other users from running CPU-intensive jobs on that host while the tests are running.

Previous: Interlocks, Up: Build Process

6.3 Build Factories

Each Builder is equipped with a “build factory”, which is responsible for producing the actual Build objects that perform each build. This factory is created in the configuration file, and attached to a Builder through the factory element of its dictionary.

The standard BuildFactory object creates Build objects by default. These Builds will each execute a collection of BuildSteps in a fixed sequence. Each step can affect the results of the build, but in general there is little intelligence to tie the different steps together. You can create subclasses of Build to implement more sophisticated build processes, and then use a subclass of BuildFactory (or simply set the buildClass attribute) to create instances of your new Build subclass.

Next: , Previous: Build Factories, Up: Build Factories

6.3.1 BuildStep Objects

The steps used by these builds are all subclasses of BuildStep. The standard ones provided with Buildbot are documented later, See Build Steps. You can also write your own subclasses to use in builds.

The basic behavior for a BuildStep is to:

More sophisticated steps may produce additional information and provide it to later build steps, or store it in the factory to provide to later builds.

Next: , Previous: BuildStep Objects, Up: Build Factories

6.3.2 BuildFactory

The default BuildFactory, provided in the buildbot.process.factory module, contains a list of “BuildStep specifications”: a list of (step_class, kwargs) tuples for each. When asked to create a Build, it loads the list of steps into the new Build object. When the Build is actually started, these step specifications are used to create the actual set of BuildSteps, which are then executed one at a time. For example, a build which consists of a CVS checkout followed by a make build would be constructed as follows:

     from buildbot.steps import source, shell
     from buildbot.process import factory
     f = factory.BuildFactory()
     f.addStep(source.CVS, cvsroot=CVSROOT, cvsmodule="project", mode="update")
     f.addStep(shell.Compile, command=["make", "build"])

It is also possible to pass a list of step specifications into the BuildFactory when it is created. Using addStep is usually simpler, but there are cases where is is more convenient to create the list of steps ahead of time. To make this approach easier, a convenience function named s is available:

     from buildbot.steps import source, shell
     from buildbot.process import factory
     from buildbot.factory import s
     # s is a convenience function, defined with:
     # def s(steptype, **kwargs): return (steptype, kwargs)
     all_steps = [s(source.CVS, cvsroot=CVSROOT, cvsmodule="project",
                  s(shell.Compile, command=["make", "build"]),
     f = factory.BuildFactory(all_steps)

Each step can affect the build process in the following ways:

In addition, each Step produces its own results, may create logfiles, etc. However only the flags described above have any effect on the build as a whole.

The pre-defined BuildSteps like CVS and Compile have reasonably appropriate flags set on them already. For example, without a source tree there is no point in continuing the build, so the CVS class has the haltOnFailure flag set to True. Look in buildbot/process/ to see how the other Steps are marked.

Each Step is created with an additional workdir argument that indicates where its actions should take place. This is specified as a subdirectory of the slave builder's base directory, with a default value of build. This is only implemented as a step argument (as opposed to simply being a part of the base directory) because the CVS/SVN steps need to perform their checkouts from the parent directory.

Next: , Previous: BuildFactory, Up: BuildFactory BuildFactory Attributes

Some attributes from the BuildFactory are copied into each Build.

(defaults to True): if True, the buildmaster keeps track of how long each step takes, so it can provide estimates of how long future builds will take. If builds are not expected to take a consistent amount of time (such as incremental builds in which a random set of files are recompiled or tested each time), this should be set to False to inhibit progress-tracking.

Previous: BuildFactory Attributes, Up: BuildFactory Quick builds

The difference between a “full build” and a “quick build” is that quick builds are generally done incrementally, starting with the tree where the previous build was performed. That simply means that the source-checkout step should be given a mode='update' flag, to do the source update in-place.

In addition to that, the useProgress flag should be set to False. Incremental builds will (or at least the ought to) compile as few files as necessary, so they will take an unpredictable amount of time to run. Therefore it would be misleading to claim to predict how long the build will take.

Previous: BuildFactory, Up: Build Factories

6.3.3 Process-Specific build factories

Many projects use one of a few popular build frameworks to simplify the creation and maintenance of Makefiles or other compilation structures. Buildbot provides several pre-configured BuildFactory subclasses which let you build these projects with a minimum of fuss.

Next: , Previous: Process-Specific build factories, Up: Process-Specific build factories GNUAutoconf

GNU Autoconf is a software portability tool, intended to make it possible to write programs in C (and other languages) which will run on a variety of UNIX-like systems. Most GNU software is built using autoconf. It is frequently used in combination with GNU automake. These tools both encourage a build process which usually looks like this:

     % CONFIG_ENV=foo ./configure --with-flags
     % make all
     % make check
     # make install

(except of course the Buildbot always skips the make install part).

The Buildbot's buildbot.process.factory.GNUAutoconf factory is designed to build projects which use GNU autoconf and/or automake. The configuration environment variables, the configure flags, and command lines used for the compile and test are all configurable, in general the default values will be suitable.


     # use the s() convenience function defined earlier
     f = factory.GNUAutoconf(source=s(step.SVN, svnurl=URL, mode="copy"),

Required Arguments:

This argument must be a step specification tuple that provides a BuildStep to generate the source tree.

Optional Arguments:

The command used to configure the tree. Defaults to ./configure. Accepts either a string or a list of shell argv elements.
The environment used for the initial configuration step. This accepts a dictionary which will be merged into the buildslave's normal environment. This is commonly used to provide things like CFLAGS="-O2 -g" (to turn off debug symbols during the compile). Defaults to an empty dictionary.
A list of flags to be appended to the argument list of the configure command. This is commonly used to enable or disable specific features of the autoconf-controlled package, like ["--without-x"] to disable windowing support. Defaults to an empty list.
this is a shell command or list of argv values which is used to actually compile the tree. It defaults to make all. If set to None, the compile step is skipped.
this is a shell command or list of argv values which is used to run the tree's self-tests. It defaults to make check. If set to None, the test step is skipped.

Next: , Previous: GNUAutoconf, Up: Process-Specific build factories CPAN

Most Perl modules available from the CPAN archive use the MakeMaker module to provide configuration, build, and test services. The standard build routine for these modules looks like:

     % perl Makefile.PL
     % make
     % make test
     # make install

(except again Buildbot skips the install step)

Buildbot provides a CPAN factory to compile and test these projects.


(required): A step specification tuple, that that used by GNUAutoconf.
A string which specifies the perl executable to use. Defaults to just perl.

Next: , Previous: CPAN, Up: Process-Specific build factories Python distutils

Most Python modules use the distutils package to provide configuration and build services. The standard build process looks like:

     % python ./ build
     % python ./ install

Unfortunately, although Python provides a standard unit-test framework named unittest, to the best of my knowledge distutils does not provide a standardized target to run such unit tests. (please let me know if I'm wrong, and I will update this factory).

The Distutils factory provides support for running the build part of this process. It accepts the same source= parameter as the other build factories.


(required): A step specification tuple, that that used by GNUAutoconf.
A string which specifies the python executable to use. Defaults to just python.
Provides a shell command which runs unit tests. This accepts either a string or a list. The default value is None, which disables the test step (since there is no common default command to run unit tests in distutils modules).

Previous: Python distutils, Up: Process-Specific build factories Python/Twisted/trial projects

Twisted provides a unit test tool named trial which provides a few improvements over Python's built-in unittest module. Many python projects which use Twisted for their networking or application services also use trial for their unit tests. These modules are usually built and tested with something like the following:

     % python ./ build
     % PYTHONPATH=build/lib.linux-i686-2.3 trial -v PROJECTNAME.test
     % python ./ install

Unfortunately, the build/lib directory into which the built/copied .py files are placed is actually architecture-dependent, and I do not yet know of a simple way to calculate its value. For many projects it is sufficient to import their libraries “in place” from the tree's base directory (PYTHONPATH=.).

In addition, the PROJECTNAME value where the test files are located is project-dependent: it is usually just the project's top-level library directory, as common practice suggests the unit test files are put in the test sub-module. This value cannot be guessed, the Trial class must be told where to find the test files.

The Trial class provides support for building and testing projects which use distutils and trial. If the test module name is specified, trial will be invoked. The library path used for testing can also be set.

One advantage of trial is that the Buildbot happens to know how to parse trial output, letting it identify which tests passed and which ones failed. The Buildbot can then provide fine-grained reports about how many tests have failed, when individual tests fail when they had been passing previously, etc.

Another feature of trial is that you can give it a series of source .py files, and it will search them for special test-case-name tags that indicate which test cases provide coverage for that file. Trial can then run just the appropriate tests. This is useful for quick builds, where you want to only run the test cases that cover the changed functionality.


(required): A step specification tuple, like that used by GNUAutoconf.
A list (argv array) of strings which specifies the python executable to use when building the package. Defaults to just ['python']. It may be useful to add flags here, to supress warnings during compilation of extension modules. This list is extended with ['./', 'build'] and then executed in a ShellCommand.
Provides a directory to add to PYTHONPATH when running the unit tests, if tests are being run. Defaults to . to include the project files in-place. The generated build library is frequently architecture-dependent, but may simply be build/lib for pure-python modules.
Another list of strings used to build the command that actually runs trial. This is prepended to the contents of the trial argument below. It may be useful to add -W flags here to supress warnings that occur while tests are being run. Defaults to an empty list, meaning trial will be run without an explicit interpreter, which is generally what you want if you're using /usr/bin/trial instead of, say, the ./bin/trial that lives in the Twisted source tree.
provides the name of the trial command. It is occasionally useful to use an alternate executable, such as trial2.2 which might run the tests under an older version of Python. Defaults to trial.
Provides a module name or names which contain the unit tests for this project. Accepts a string, typically PROJECTNAME.test, or a list of strings. Defaults to None, indicating that no tests should be run. You must either set this or useTestCaseNames to do anyting useful with the Trial factory.
Tells the Step to provide the names of all changed .py files to trial, so it can look for test-case-name tags and run just the matching test cases. Suitable for use in quick builds. Defaults to False.
If True, tells Trial (with the --random=0 argument) to run the test cases in random order, which sometimes catches subtle inter-test dependency bugs. Defaults to False.
If True, tells Trial (with the --recurse argument) to look in all subdirectories for additional test cases. It isn't clear to me how this works, but it may be useful to deal with the unknown-PROJECTNAME problem described above, and is currently used in the Twisted buildbot to accomodate the fact that test cases are now distributed through multiple twisted.SUBPROJECT.test directories.

Unless one of trialModule or useTestCaseNames are set, no tests will be run.

Some quick examples follow. Most of these examples assume that the target python code (the “code under test”) can be reached directly from the root of the target tree, rather than being in a lib/ subdirectory.

     #  Trial(source, tests="toplevel.test") does:
     #   python ./ build
     #   PYTHONPATH=. trial -to toplevel.test
     #  Trial(source, tests=["toplevel.test", "other.test"]) does:
     #   python ./ build
     #   PYTHONPATH=. trial -to toplevel.test other.test
     #  Trial(source, useTestCaseNames=True) does:
     #   python ./ build
     #   PYTHONPATH=. trial -to --testmodule=foo/  (from Changes)
     #  Trial(source, buildpython=["python2.3", "-Wall"], tests="foo.tests"):
     #   python2.3 -Wall ./ build
     #   PYTHONPATH=. trial -to foo.tests
     #  Trial(source, trialpython="python2.3", trial="/usr/bin/trial",
     #        tests="foo.tests") does:
     #   python2.3 -Wall ./ build
     #   PYTHONPATH=. python2.3 /usr/bin/trial -to foo.tests
     # For running trial out of the tree being tested (only useful when the
     # tree being built is Twisted itself):
     #  Trial(source, trialpython=["python2.3", "-Wall"], trial="./bin/trial",
     #        tests="foo.tests") does:
     #   python2.3 -Wall ./ build
     #   PYTHONPATH=. python2.3 -Wall ./bin/trial -to foo.tests

If the output directory of ./ build is known, you can pull the python code from the built location instead of the source directories. This should be able to handle variations in where the source comes from, as well as accomodating binary extension modules:

     # Trial(source,tests="toplevel.test",testpath='build/lib.linux-i686-2.3')
     # does:
     #  python ./ build
     #  PYTHONPATH=build/lib.linux-i686-2.3 trial -to toplevel.test

Next: , Previous: Build Process, Up: Top

7 Status Delivery

More details are available in the docstrings for each class, use pydoc buildbot.status.html.Waterfall to see them. Most status delivery objects take a categories= argument, which can contain a list of “category” names: in this case, it will only show status for Builders that are in one of the named categories.

(implementor's note: each of these objects should be a service.MultiService which will be attached to the BuildMaster object when the configuration is processed. They should use self.parent.getStatus() to get access to the top-level IStatus object, either inside startService or later. They may call status.subscribe() in startService to receive notifications of builder events, in which case they must define builderAdded and related methods. See the docstrings in buildbot/ for full details.)

Next: , Previous: Status Delivery, Up: Status Delivery

7.1 HTML Waterfall

     from buildbot.status import html
     w = html.Waterfall(http_port=8080)

The buildbot.status.html.Waterfall status target creates an HTML “waterfall display”, which shows a time-based chart of events. This display provides detailed information about all steps of all recent builds, and provides hyperlinks to look at individual build logs and source changes. If the http_port argument is provided, it provides a strports specification for the port that the web server should listen on. This can be a simple port number, or a string like tcp:8080:interface= (to limit connections to the loopback interface, and therefore to clients running on the same host)11.

If instead (or in addition) you provide the distrib_port argument, a twisted.web distributed server will be started either on a TCP port (if distrib_port is like "tcp:12345") or more likely on a UNIX socket (if distrib_port is like "unix:/path/to/socket").

The distrib_port option means that, on a host with a suitably-configured twisted-web server, you do not need to consume a separate TCP port for the buildmaster's status web page. When the web server is constructed with mktap web --user, URLs that point to http://host/~username/ are dispatched to a sub-server that is listening on a UNIX socket at ~username/.twisted-web-pb. On such a system, it is convenient to create a dedicated buildbot user, then set distrib_port to "unix:"+os.path.expanduser("~/.twistd-web-pb"). This configuration will make the HTML status page available at http://host/~buildbot/ . Suitable URL remapping can make it appear at http://host/buildbot/, and the right virtual host setup can even place it at .

Other arguments:

If set to True (the default), then the web page will provide a “Force Build” button that allows visitors to manually trigger builds. This is useful for developers to re-run builds that have failed because of intermittent problems in the test suite, or because of libraries that were not installed at the time of the previous build. You may not wish to allow strangers to cause a build to run: in that case, set this to False to remove these buttons.
If set to a string, this will be interpreted as a filename containing a “favicon”: a small image that contains an icon for the web site. This is returned to browsers that request the favicon.ico file, and should point to a .png or .ico image file. The default value uses the buildbot/buildbot.png image (a small hex nut) contained in the buildbot distribution. You can set this to None to avoid using a favicon at all.
If set to a string, this will be interpreted as a filename containing the contents of “robots.txt”. Many search engine spiders request this file before indexing the site. Setting it to a file which contains:
          User-agent: *
          Disallow: /

will prevent most search engines from trawling the (voluminous) generated status pages.

Next: , Previous: HTML Waterfall, Up: Status Delivery

7.2 IRC Bot

The buildbot.status.words.IRC status target creates an IRC bot which will attach to certain channels and be available for status queries. It can also be asked to announce builds as they occur, or be told to shut up.

     from twisted.status import words
     irc = words.IRC("", "botnickname",
                     channels=["channel1", "channel2"],

Take a look at the docstring for words.IRC for more details on configuring this service. The password argument, if provided, will be sent to Nickserv to claim the nickname: some IRC servers will not allow clients to send private messages until they have logged in with a password.

To use the service, you address messages at the buildbot, either normally (botnickname: status) or with private messages (/msg botnickname status). The buildbot will respond in kind.

Some of the commands currently available:

list builders
Emit a list of all configured builders
status BUILDER
Announce the status of a specific Builder: what it is doing right now.
status all
Announce the status of all Builders
If the given Builder is currently running, wait until the Build is finished and then announce the results.
Return the results of the last build to run on the given Builder.
Describe a command. Use help commands to get a list of known commands.
Announce the URL of the Buildbot's home page.
Announce the version of this Buildbot.

If the allowForce=True option was used, some addtional commands will be available:

force build BUILDER REASON
Tell the given Builder to start a build of the latest code. The user requesting the build and REASON are recorded in the Build status. The buildbot will announce the build's status when it finishes.
Terminate any running build in the given Builder. REASON will be added to the build status to explain why it was stopped. You might use this if you committed a bug, corrected it right away, and don't want to wait for the first build (which is destined to fail) to complete before starting the second (hopefully fixed) build.

Next: , Previous: IRC Bot, Up: Status Delivery

7.3 PBListener

     import buildbot.status.client
     pbl = buildbot.status.client.PBListener(port=int, user=str,

This sets up a PB listener on the given TCP port, to which a PB-based status client can connect and retrieve status information. buildbot statusgui (see statusgui) is an example of such a status client. The port argument can also be a strports specification string.

Previous: PBListener, Up: Status Delivery

7.4 Writing New Status Plugins

TODO: this needs a lot more examples

Each status plugin is an object which provides the twisted.application.service.IService interface, which creates a tree of Services with the buildmaster at the top [not strictly true]. The status plugins are all children of an object which implements buildbot.interfaces.IStatus, the main status object. From this object, the plugin can retrieve anything it wants about current and past builds. It can also subscribe to hear about new and upcoming builds.

Status plugins which only react to human queries (like the Waterfall display) never need to subscribe to anything: they are idle until someone asks a question, then wake up and extract the information they need to answer it, then they go back to sleep. Plugins which need to act spontaneously when builds complete (like the Mail plugin) need to subscribe to hear about new builds.

If the status plugin needs to run network services (like the HTTP server used by the Waterfall plugin), they can be attached as Service children of the plugin itself, using the IServiceCollection interface.

Next: , Previous: Status Delivery, Up: Top

8 Command-line tool

The buildbot command-line tool can be used to start or stop a buildmaster or buildbot, and to interact with a running buildmaster. Some of its subcommands are intended for buildmaster admins, while some are for developers who are editing the code that the buildbot is monitoring.

Next: , Previous: Command-line tool, Up: Command-line tool

8.1 Administrator Tools

The following buildbot sub-commands are intended for buildmaster administrators:


This creates a new directory and populates it with files that allow it to be used as a buildmaster's base directory.

     buildbot create-master BASEDIR


This creates a new directory and populates it with files that let it be used as a buildslave's base directory. You must provide several arguments, which are used to create the initial buildbot.tac file.



This starts a buildmaster or buildslave which was already created in the given base directory. The daemon is launched in the background, with events logged to a file named twistd.log.

     buildbot start BASEDIR


This terminates the daemon (either buildmaster or buildslave) running in the given directory.

     buildbot stop BASEDIR


This sends a SIGHUP to the buildmaster running in the given directory, which causes it to re-read its master.cfg file.

     buildbot sighup BASEDIR

Next: , Previous: Administrator Tools, Up: Command-line tool

8.2 Developer Tools

These tools are provided for use by the developers who are working on the code that the buildbot is monitoring.

Next: , Previous: Developer Tools, Up: Developer Tools

8.2.1 statuslog

     buildbot statuslog --master MASTERHOST:PORT

This command starts a simple text-based status client, one which just prints out a new line each time an event occurs on the buildmaster.

The --master option provides the location of the buildbot.status.client.PBListener status port, used to deliver build information to realtime status clients. The option is always in the form of a string, with hostname and port number separated by a colon (HOSTNAME:PORTNUM). Note that this port is not the same as the slaveport (although a future version may allow the same port number to be used for both purposes). If you get an error message to the effect of “Failure: twisted.cred.error.UnauthorizedLogin:”, this may indicate that you are connecting to the slaveport rather than a PBListener port.

The --master option can also be provided by the masterstatus name in .buildbot/options (see .buildbot config directory).

Next: , Previous: statuslog, Up: Developer Tools

8.2.2 statusgui

If you have set up a PBListener (see PBListener), you will be able to monitor your Buildbot using a simple Gtk+ application invoked with the buildbot statusgui command:

     buildbot statusgui --master MASTERHOST:PORT

This command starts a simple Gtk+-based status client, which contains a few boxes for each Builder that change color as events occur. It uses the same --master argument as the buildbot statuslog command (see statuslog).

Previous: statusgui, Up: Developer Tools

8.2.3 try

This lets a developer to ask the question “What would happen if I committed this patch right now?”. It runs the unit test suite (across multiple build platforms) on the developer's current code, allowing them to make sure they will not break the tree when they finally commit their changes.

The buildbot try command is meant to be run from within a developer's local tree, and starts by figuring out the base revision of that tree (what revision was current the last time the tree was updated), and a patch that can be applied to that revision of the tree to make it match the developer's copy. This (revision, patch) pair is then sent to the buildmaster, which runs a build with that SourceStamp. If you want, the tool will emit status messages as the builds run, and will not terminate until the first failure has been detected (or the last success).

For this command to work, several pieces must be in place:


The buildmaster must have a scheduler.Try instance in the config file's c['schedulers'] list. This lets the administrator control who may initiate these “trial” builds, which branches are eligible for trial builds, and which Builders should be used for them.

The TryScheduler has various means to accept build requests: all of them enforce more security than the usual buildmaster ports do. Any source code being built can be used to compromise the buildslave accounts, but in general that code must be checked out from the VC repository first, so only people with commit privileges can get control of the buildslaves. The usual force-build control channels can waste buildslave time but do not allow arbitrary commands to be executed by people who don't have those commit privileges. However, the source code patch that is provided with the trial build does not have to go through the VC system first, so it is important to make sure these builds cannot be abused by a non-committer to acquire as much control over the buildslaves as a committer has. Ideally, only developers who have commit access to the VC repository would be able to start trial builds, but unfortunately the buildmaster does not, in general, have access to VC system's user list.

As a result, the TryScheduler requires a bit more configuration. There are currently two ways to set this up:

jobdir (ssh)
This approach creates a command queue directory, called the “jobdir”, in the buildmaster's working directory. The buildmaster admin sets the ownership and permissions of this directory to only grant write access to the desired set of developers, all of whom must have accounts on the machine. The buildbot try command creates a special file containing the source stamp information and drops it in the jobdir, just like a standard maildir. When the buildmaster notices the new file, it unpacks the information inside and starts the builds.

The config file entries used by 'buildbot try' either specify a local queuedir (for which write and mv are used) or a remote one (using scp and ssh).

The advantage of this scheme is that it is quite secure, the disadvantage is that it requires fiddling outside the buildmaster config (to set the permissions on the jobdir correctly). If the buildmaster machine happens to also house the VC repository, then it can be fairly easy to keep the VC userlist in sync with the trial-build userlist. If they are on different machines, this will be much more of a hassle. It may also involve granting developer accounts on a machine that would not otherwise require them.

To implement this, the buildslave invokes 'ssh -l username host buildbot tryserver ARGS', passing the patch contents over stdin. The arguments must include the inlet directory and the revision information.

user+password (PB)
In this approach, each developer gets a username/password pair, which are all listed in the buildmaster's configuration file. When the developer runs buildbot try, their machine connects to the buildmaster via PB and authenticates themselves using that username and password, then sends a PB command to start the trial build.

The advantage of this scheme is that the entire configuration is performed inside the buildmaster's config file. The disadvantages are that it is less secure (while the “cred” authentication system does not expose the password in plaintext over the wire, it does not offer most of the other security properties that SSH does). In addition, the buildmaster admin is responsible for maintaining the username/password list, adding and deleting entries as developers come and go.

For example, to set up the “jobdir” style of trial build, using a command queue directory of MASTERDIR/jobdir (and assuming that all your project developers were members of the developers unix group), you would first create that directory (with mkdir MASTERDIR/jobdir MASTERDIR/jobdir/new MASTERDIR/jobdir/cur MASTERDIR/jobdir/tmp; chgrp developers MASTERDIR/jobdir MASTERDIR/jobdir/*; chmod g+rwx,o-rwx MASTERDIR/jobdir MASTERDIR/jobdir/*), and then use the following scheduler in the buildmaster's config file:

     from buildbot.scheduler import Try_Jobdir
     s = Try_Jobdir("try1", ["full-linux", "full-netbsd", "full-OSX"],
     c['schedulers'] = [s]

Note that you must create the jobdir before telling the buildmaster to use this configuration, otherwise you will get an error. Also remember that the buildmaster must be able to read and write to the jobdir as well. Be sure to watch the twistd.log file (see Logfiles) as you start using the jobdir, to make sure the buildmaster is happy with it.

To use the username/password form of authentication, create a Try_Userpass instance instead. It takes the same builderNames argument as the Try_Jobdir form, but accepts an addtional port argument (to specify the TCP port to listen on) and a userpass list of username/password pairs to accept. Remember to use good passwords for this: the security of the buildslave accounts depends upon it:

     from buildbot.scheduler import Try_Userpass
     s = Try_Userpass("try2", ["full-linux", "full-netbsd", "full-OSX"],
                      port=8031, userpass=[("alice","pw1"), ("bob", "pw2")] )
     c['schedulers'] = [s]

Like most places in the buildbot, the port argument takes a strports specification. See twisted.application.strports for details.

locating the master

The try command needs to be told how to connect to the TryScheduler, and must know which of the authentication approaches described above is in use by the buildmaster. You specify the approach by using --connect=ssh or --connect=pb (or try_connect = 'ssh' or try_connect = 'pb' in .buildbot/options).

For the PB approach, the command must be given a --master argument (in the form HOST:PORT) that points to TCP port that you picked in the Try_Userpass scheduler. It also takes a --username and --passwd pair of arguments that match one of the entries in the buildmaster's userpass list. These arguments can also be provided as try_master, try_username, and try_password entries in the .buildbot/options file.

For the SSH approach, the command must be given --tryhost, --username, and optionally --password (TODO: really?) to get to the buildmaster host. It must also be given --trydir, which points to the inlet directory configured above. The trydir can be relative to the user's home directory, but most of the time you will use an explicit path like ~buildbot/project/trydir. These arguments can be provided in .buildbot/options as try_host, try_username, try_password, and try_dir.

In addition, the SSH approach needs to connect to a PBListener status port, so it can retrieve and report the results of the build (the PB approach uses the existing connection to retrieve status information, so this step is not necessary). This requires a --master argument, or a masterstatus entry in .buildbot/options, in the form of a HOSTNAME:PORT string.

choosing the Builders

A trial build is performed on multiple Builders at the same time, and the developer gets to choose which Builders are used (limited to a set selected by the buildmaster admin with the TryScheduler's builderNames= argument). The set you choose will depend upon what your goals are: if you are concerned about cross-platform compatibility, you should use multiple Builders, one from each platform of interest. You might use just one builder if that platform has libraries or other facilities that allow better test coverage than what you can accomplish on your own machine, or faster test runs.

The set of Builders to use can be specified with multiple --builder arguments on the command line. It can also be specified with a single try_builders option in .buildbot/options that uses a list of strings to specify all the Builder names:

     try_builders = ["full-OSX", "full-win32", "full-linux"]

specifying the VC system

The try command also needs to know how to take the developer's current tree and extract the (revision, patch) source-stamp pair. Each VC system uses a different process, so you start by telling the try command which VC system you are using, with an argument like --vc=cvs or --vc=tla. This can also be provided as try_vc in .buildbot/options.

The following names are recognized: cvs svn baz tla hg darcs

finding the top of the tree

Some VC systems (notably CVS and SVN) track each directory more-or-less independently, which means the try command needs to move up to the top of the project tree before it will be able to construct a proper full-tree patch. To accomplish this, the try command will crawl up through the parent directories until it finds a marker file. The default name for this marker file is .buildbot-top, so when you are using CVS or SVN you should touch .buildbot-top from the top of your tree before running buildbot try. Alternatively, you can use a filename like ChangeLog or README, since many projects put one of these files in their top-most directory (and nowhere else). To set this filename, use --try-topfile=ChangeLog, or set it in the options file with try_topfile = 'ChangeLog'.

You can also manually set the top of the tree with --try-topdir=~/trees/mytree, or try_topdir = '~/trees/mytree'. If you use try_topdir, in a .buildbot/options file, you will need a separate options file for each tree you use, so it may be more convenient to use the try_topfile approach instead.

Other VC systems which work on full projects instead of individual directories (tla, baz, darcs, monotone, mercurial) do not require try to know the top directory, so the --try-topfile and --try-topdir arguments will be ignored.

If the try command cannot find the top directory, it will abort with an error message.

determining the branch name

Some VC systems record the branch information in a way that “try” can locate it, in particular Arch (both tla and baz). For the others, if you are using something other than the default branch, you will have to tell the buildbot which branch your tree is using. You can do this with either the --branch argument, or a try_branch entry in the .buildbot/options file.

determining the revision and patch

Each VC system has a separate approach for determining the tree's base revision and computing a patch.

try pretends that the tree is up to date. It converts the current time into a -D time specification, uses it as the base revision, and computes the diff between the upstream tree as of that point in time versus the current contents. This works, more or less, but requires that the local clock be in reasonably good sync with the repository.
try does a svn status -u to find the latest repository revision number (emitted on the last line in the “Status against revision: NN” message). It then performs an svn diff -rNN to find out how your tree differs from the repository version, and sends the resulting patch to the buildmaster. If your tree is not up to date, this will result in the “try” tree being created with the latest revision, then backwards patches applied to bring it “back” to the version you actually checked out (plus your actual code changes), but this will still result in the correct tree being used for the build.
try does a baz tree-id to determine the fully-qualified version and patch identifier for the tree (ARCHIVE/VERSION–patch-NN), and uses the VERSION–patch-NN component as the base revision. It then does a baz diff to obtain the patch.
try does a tla tree-version to get the fully-qualified version identifier (ARCHIVE/VERSION), then takes the first line of tla logs --reverse to figure out the base revision. Then it does tla changes --diffs to obtain the patch.
darcs changes --context emits a text file that contains a list of all patches back to and including the last tag was made. This text file (plus the location of a repository that contains all these patches) is sufficient to re-create the tree. Therefore the contents of this “context” file are the revision stamp for a Darcs-controlled source tree.

So try does a darcs changes --context to determine what your tree's base revision is, and then does a darcs diff -u to compute the patch relative to that revision.

hg identify emits a short revision ID (basically a truncated SHA1 hash of the current revision's contents), which is used as the base revision. hg diff then provides the patch relative to that revision. For try to work, your working directory must only have patches that are available from the same remotely-available repository that the build process' step.Mercurial will use.

waiting for results

If you provide the --wait option (or try_wait = True in .buildbot/options), the buildbot try command will wait until your changes have either been proven good or bad before exiting. Unless you use the --quiet option (or try_quiet=True), it will emit a progress message every 60 seconds until the builds have completed.

Next: , Previous: Developer Tools, Up: Command-line tool

8.3 Other Tools

These tools are generally used by buildmaster administrators.

Next: , Previous: Other Tools, Up: Other Tools

8.3.1 sendchange

This command is used to tell the buildmaster about source changes. It is intended to be used from within a commit script, installed on the VC server. It requires that you have a PBChangeSource (see PBChangeSource) running in the buildmaster (by being included in the c['sources'] list).

     buildbot sendchange --master MASTERHOST:PORT --username USER FILENAMES..

There are other (optional) arguments which can influence the Change that gets submitted:

This provides the (string) branch specifier. If omitted, it defaults to None, indicating the “default branch”. All files included in this Change must be on the same branch.
This provides a (numeric) revision number for the change, used for VC systems that use numeric transaction numbers (like Subversion).
This provides a (string) revision specifier, for VC systems that use strings (Arch would use something like patch-42 etc).
This provides a filename which will be opened and the contents used as the revision specifier. This is specifically for Darcs, which uses the output of darcs changes --context as a revision specifier. This context file can be a couple of kilobytes long, spanning a couple lines per patch, and would be a hassle to pass as a command-line argument.
This provides the change comments as a single argument. You may want to use --logfile instead.
This instructs the tool to read the change comments from the given file. If you use - as the filename, the tool will read the change comments from stdin.

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8.3.2 debugclient

     buildbot debugclient --master MASTERHOST:PORT --passwd DEBUGPW

This launches a small Gtk+/Glade-based debug tool, connecting to the buildmaster's “debug port”. This debug port shares the same port number as the slaveport (see Setting the slaveport), but the debugPort is only enabled if you set a debug password in the buildmaster's config file (see Debug options). The --passwd option must match the c['debugPassword'] value.

--master can also be provided in .debug/options by the master key. --passwd can be provided by the debugPassword key.

The Connect button must be pressed before any of the other buttons will be active. This establishes the connection to the buildmaster. The other sections of the tool are as follows:

Reload .cfg
Forces the buildmaster to reload its master.cfg file. This is equivalent to sending a SIGHUP to the buildmaster, but can be done remotely through the debug port. Note that it is a good idea to be watching the buildmaster's twistd.log as you reload the config file, as any errors which are detected in the config file will be announced there.
Rebuild .py
(not yet implemented). The idea here is to use Twisted's “rebuild” facilities to replace the buildmaster's running code with a new version. Even if this worked, it would only be used by buildbot developers.
poke IRC
This locates a words.IRC status target and causes it to emit a message on all the channels to which it is currently connected. This was used to debug a problem in which the buildmaster lost the connection to the IRC server and did not attempt to reconnect.
This allows you to inject a Change, just as if a real one had been delivered by whatever VC hook you are using. You can set the name of the committed file and the name of the user who is doing the commit. Optionally, you can also set a revision for the change. If the revision you provide looks like a number, it will be sent as an integer, otherwise it will be sent as a string.
Force Build
This lets you force a Builder (selected by name) to start a build of the current source tree.
(obsolete). This was used to manually set the status of the given Builder, but the status-assignment code was changed in an incompatible way and these buttons are no longer meaningful.

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8.4 .buildbot config directory

Many of the buildbot tools must be told how to contact the buildmaster that they interact with. This specification can be provided as a command-line argument, but most of the time it will be easier to set them in an “options” file. The buildbot command will look for a special directory named .buildbot, starting from the current directory (where the command was run) and crawling upwards, eventually looking in the user's home directory. It will look for a file named options in this directory, and will evaluate it as a python script, looking for certain names to be set. You can just put simple name = 'value' pairs in this file to set the options.

For a description of the names used in this file, please see the documentation for the individual buildbot sub-commands. The following is a brief sample of what this file's contents could be.

     # for status-reading tools
     masterstatus = ''
     # for 'sendchange' or the debug port
     master = ''
     debugPassword = 'eiv7Po'
Location of the client.PBListener status port, used by statuslog and statusgui.
Location of the debugPort (for debugclient). Also the location of the pb.PBChangeSource (for sendchange). Usually shares the slaveport, but a future version may make it possible to have these listen on a separate port number.
Must match the value of c['debugPassword'], used to protect the debug port, for the debugclient command.
Provides a default username for the sendchange command.

The following options are used by the buildbot try command (see try):

This specifies how the “try” command should deliver its request to the buildmaster. The currently accepted values are “ssh” and “pb”.
Which builders should be used for the “try” build.
This specifies the version control system being used.
This indicates that the current tree is on a non-trunk branch.
Use try_topdir to explicitly indicate the top of your working tree, or try_topfile to name a file that will only be found in that top-most directory.
When try_connect is “ssh”, the command will pay attention to try_host, try_username, and try_dir.
Instead, when try_connect is “pb”, the command will pay attention to try_username, try_password, and try_master.
try_wait and masterstatus are used to ask the “try” command to wait for the requested build to complete.

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9 Resources

The Buildbot's home page is at

For configuration questions and general discussion, please use the buildbot-devel mailing list. The subscription instructions and archives are available at

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Developer's Appendix

This appendix contains random notes about the implementation of the Buildbot, and is likely to only be of use to people intending to extend the Buildbot's internals.

The buildmaster consists of a tree of Service objects, which is shaped as follows:

      ChangeMaster  (in .change_svc)
       [IChangeSource instances]
      [IScheduler instances]  (in .schedulers)
      BotMaster  (in .botmaster)
      [IStatusTarget instances]  (in .statusTargets)

The BotMaster has a collection of Builder objects as values of its .builders dictionary.

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Index of Useful Classes

This is a list of all user-visible classes. There are the ones that are useful in master.cfg, the buildmaster's configuration file. Classes that are not listed here are generally internal things that admins are unlikely to have much use for.

Change Sources

Schedulers and Locks

Build Factories

Build Steps

Status Targets

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Index of master.cfg keys

This is a list of all of the significant keys in master.cfg . Recall that master.cfg is effectively a small python program one responsibility: create a dictionary named BuildmasterConfig. The keys of this dictionary are listed here. The beginning of the master.cfg file typically starts with something like:

     BuildmasterConfig = c = {}

Therefore a config key of sources will usually appear in master.cfg as c['sources'].

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[1] this @reboot syntax is understood by Vixie cron, which is the flavor usually provided with linux systems. Other unices may have a cron that doesn't understand @reboot

[2] except Darcs, but since the Buildbot never modifies its local source tree we can ignore the fact that Darcs uses a less centralized model

[3] many VC systems provide more complexity than this: in particular the local views that P4 and ClearCase can assemble out of various source directories are more complex than we're prepared to take advantage of here

[4] Monotone's multiple heads feature violates this assumption of cumulative Changes, but in most situations the changes don't occur frequently enough for this to be a significant problem

[5] this checkoutDelay defaults to half the tree-stable timer, but it can be overridden with an argument to the Source Step

[6] To be precise, it is a list of objects which all implement the buildbot.interfaces.IChangeSource Interface

[7] Build properties are serialized along with the build results, so they must be serializable. For this reason, the value of any build property should be simple inert data: strings, numbers, lists, tuples, and dictionaries. They should not contain class instances.

[8] is still available. Remember, I get 10% :).

[9] Framboozle gets very excited about running unit tests.

[10] Also note that a clever buildmaster admin could still create the opportunity for deadlock: Build A obtains Lock 1, inside which Step A.two tries to acquire Lock 2 at the Step level. Meanwhile Build B obtains Lock 2, and has a Step B.two which wants to acquire Lock 1 at the Step level. Don't Do That.

[11] It may even be possible to provide SSL access by using a specification like "ssl:12345:privateKey=mykey.pen:certKey=cert.pem", but this is completely untested