Buildbot no longer supports Python 2.7 on the Buildbot master.

3.1. Development Quick-start

Buildbot is a python based application. It tries very hard to follow the python best practices, and to make is easy to dive into the code.

In order to develop Buildbot you need just a python environment and possibly some native packages in stripped-down setups. The most up to date list in the docker file we use to manage our CI (MetaBBotDockerFile).

If you are completely new to python, the best is to first follow the tutorials that would come when you type “python virtualenv for dummies” in your favorite search engine.

3.1.1. Create a Buildbot Python Environment

Buildbot uses Twisted trial to run its test suite.

Following is a quick shell session to put you on the right track, including running the test suite.

# the usual buildbot development bootstrap with git and virtualenv
git clone
cd buildbot

# run a helper script which creates the virtualenv for development.
# Virtualenv allows to install python packages without affecting
# other parts of the system
make virtualenv

# Activate the virtualenv.
# After this you should see (.venv) in your shell prompt
. .venv/bin/activate

# now we run the test suite
trial buildbot

# using all CPU cores within the system helps to speed everything up
trial -j16 buildbot

# find all tests that talk about mail
trial -n --reporter=bwverbose buildbot | grep mail

# run only one test module
trial buildbot.test.unit.test_reporters_mail

# you can also skip the virtualenv activation using make
make trial

# and pass options using TRIALOPTS
make trial TRIALOPTS='-j16 buildbot'

# or test with a specific Python version
make trial VENV_PY_VERSION=/usr/local/bin/python3

3.1.2. Create a JavaScript Frontend Environment

This section describes how to get set up quickly to hack on the JavaScript UI. It does not assume familiarity with Python, although a Python installation is required, as well as virtualenv. You will also need NodeJS, and yarn installed. Prerequisites


Buildbot UI requires at least node 4 or newer and yarn.

  • Install LTS release of node.js. is a good start for Windows and OSX.

    For modern Linux distributions you can often simply install distribution-provided node version, if it’s recent enough. You can use yarn from the same source. The below method has been tested on Ubuntu 18.04 and should work on recent enough Debian.

    sudo apt install nodejs yarn

    In other cases, use Hacking the Buildbot JavaScript

To effectively develop Buildbot JavaScript, you’ll need a running Buildmaster, configured to operate out of the source directory.

Follow Create a Buildbot Python Environment as a prerequisite.

This should have created and enabled virtualenv Python environment.

Next, install the Buildbot-WWW and Buildbot python packages using --editable mode, which means that they should execute from the source directory.

make frontend

This will fetch a number of python dependencies from pypi, the Python package repository and also a number of node.js dependencies that are used for building the web application. Then the actual frontend code will be built with artifacts stored in the source directory, e.g. www/base/buildbot_www/static. Finally, the built python packages will be installed to virtualenv environment as --editable packages. This means that the webserver will load resources from www/base/buildbot_www/static.

Now you’ll need to create a master instance. For a bit more detail, see the Buildbot tutorial (First Run).

mkdir test-master
buildbot create-master test-master
mv test-master/master.cfg.sample test-master/master.cfg
buildbot start test-master

If all goes well, the master will start up and begin running in the background. During make frontend the www frontend was built using production mode, so everything is minified and hard to debug. However, the frontend was installed as a editable python package, so all changes in the artifacts (e.g. www/base/buildbot_www/static) in the source directories will be observed in the browser. Thus we can rebuild the JavaScript resources manually using development settings, so they are not minified and easier to debug.

This can be done by running the following in e.g. www/base directory:

yarn run build-dev

The above rebuilds the resources only once, after each change you need to refresh the built resources. The actual commands that are ran are stored in the package.json file under the scripts key.

To avoid the need to type the above command after each change, you can use the following:

yarn run dev

This will watch files for changes and reload automatically.

To run unit tests, do the following:

yarn run test

To run unit tests within all frontend packages within Buildbot, do the following at the root of the project:

make frontend_tests


You need to have Chrome-based browser installed in order to run unit tests in the default configuration.