2.2.7. Next Steps Launching the daemons

Both the buildmaster and the worker run as daemon programs. To launch them, pass the working directory to the buildbot and buildbot-worker commands, as appropriate:

# start a master
buildbot start [ BASEDIR ]
# start a worker
buildbot-worker start [ WORKER_BASEDIR ]

The BASEDIR is option and can be omitted if the current directory contains the buildbot configuration (the buildbot.tac file).

buildbot start

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 twistd.pid that should be created in the working directory. twistd.pid contains the process ID of the newly-spawned daemon.

When the worker connects to the buildmaster, new directories will start appearing in its base directory. The buildmaster tells the worker to create a directory for each Builder which will be using that worker. 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 entry [1]

@reboot buildbot start [ BASEDIR ]

When you run crontab to set this up, remember to do it as the buildmaster or worker 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 worker 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 worker 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.

Some distributions may include conveniences to make starting buildbot at boot time easy. For instance, with the default buildbot package in Debian-based distributions, you may only need to modify /etc/default/buildbot (see also /etc/init.d/buildbot, which reads the configuration in /etc/default/buildbot).

Buildbot also comes with its own init scripts that provide support for controlling multi-worker and multi-master setups (mostly because they are based on the init script from the Debian package). With a little modification these scripts can be used both on Debian and RHEL-based distributions and may thus prove helpful to package maintainers who are working on buildbot (or those that haven’t yet split buildbot into master and worker packages).

# install as /etc/default/buildbot-worker
#         or /etc/sysconfig/buildbot-worker

# install as /etc/default/buildmaster
#         or /etc/sysconfig/buildmaster

# install as /etc/init.d/buildbot-worker

# install as /etc/init.d/buildmaster

# ... and tell sysvinit about them
chkconfig buildmaster reset
# ... or
update-rc.d buildmaster defaults 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. Shutdown

To stop a buildmaster or worker manually, use:

buildbot stop [ BASEDIR ]
# or
buildbot-worker stop [ WORKER_BASEDIR ]

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

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

The buildmaster will respond to a SIGHUP by re-reading its config file. Of course, this only works on Unix-like systems with signal support, and won’t work on Windows. 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 worker 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 ]

Workers can similarly be restarted with:

buildbot-worker restart [ BASEDIR ]

There are certain configuration changes that are not handled cleanly by buildbot reconfig. If this occurs, buildbot restart is a more robust tool to fully switch over to the new configuration.

buildbot restart may also be used to start a stopped Buildbot instance. This behaviour is useful when writing scripts that stop, start and restart Buildbot.

A worker may also be gracefully shutdown from the web UI. This is useful to shutdown a worker without interrupting any current builds. The buildmaster will wait until the worker is finished all its current builds, and will then tell the worker to shutdown.

[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