Migrating python.org to buildbot 9 and python 3

Migrating Python.org to
Buildbot 9 and Python 3
By Craig Rodrigues

Presentation Overview
● Buildbot is build automation software written in Python that can be used to
build and test a software project
● Python.org uses buildbot to build CPython
● Presentation covers my efforts to update Buildbot from version 8 to
version 9, and update underlying runtime to Python 3

Buildbot Intro
● Build automation software written in Python
● Open Source project, over 12 years old:
https://buildbot.net
● Used by many projects: Chromium, LLVM, XEmacs,
Python (CPython)

What does Buildbot do?
● As changes are submitted to a large software project,
Buildbot can execute functions to answer the following
questions:
○ Does the code build?
○ Does the code pass tests and work?

How does Python.org use Buildbot?
● Source code for Python (CPython) is stored in Git on GitHub
● Developers submit changes to the code via GitHub pull requests
● Buildbot detects these changes, builds the code, and runs tests
● Many platforms, operating systems, and CPU architectures are tested
https://buildbot.python.org/all/#/console

Who maintains this?
● Python.org has an ops team, made up of volunteers
● A subset of this team is responsible for Buildbot::
python-buildbots@python.org
● Buildbot master is maintained by this team
● Buildbot workers are supplied by volunteers around the world

Moving to Buildbot 9 and
Python 3

Motivation
● Python.org was using Buildbot 8
○ Older version
○ Buildbot maintainers not updating, fixing, or doing new releases
○ Only runs on Python 2
● Newer version is Buildbot 9
○ Actively supported, fixed, new releases
○ Python 2, and now Python 3 support
○ Support newer features like Docker
○ New UI in Javascript/Angular

Migration strategy
● Port Buildbot dependencies to Python 3, primarily Twisted
○ Buildbot heavily uses Twisted for asyncio, networking
● Port Buildbot code to Python 3
● Port Python.org’s config to Buildbot 3
● Work with ops team to migrate buildbot.python.org

Port Twisted to Python 3
● See:
https://www.slideshare.net/CraigRodrigues1/the-onward-journey-porting-t
wisted-to-python-3
● Hundreds of pull requests. I did a lot of work in 2016. Got help from
others such as Glyph, Amber Brown, and others

Port Buildbot to Python 3
● Hundreds of pull requests. I did the work in 2017.
● Usual Python 3 porting challenges:
○ print “” vs. print(“”)
○ cmp() gone in Py3
○ str is now unicode in Python 3 (argh!!)
○ etc.

Buildbot interop with Python 2 workers
● Due to str/bytes (Py2) vs. str/unicode (Py3) issues, retaining
interoperability between Python 3 master, and Python 2 workers required
careful testing and bug fixing

Finding a bug in Python 3!
● I stumbled across this 7 year old bug:
https://bugs.python.org/issue10544
● This line worked in Py2 but not in Py3:
defer.returnValue([(yield self.db2data(br)) for br in buildrequests])

● Needed to be rewritten to work on Py2 and Py3:
results = []
for br in buildrequests:
results.append((yield self.db2data(br)))
defer.returnValue(results)

● https://bugs.python.org/issue10544
● Patch was committed to Python 3.7 in December 2017 to deprecate the
original code snippet that worked in Python 2

Doing the final migration for
Python.org

Porting the config
● Buildbot config is Python code, so minor porting required
● Buildbot nine UI is written in JavaScript/Angular, makes heavy use of
websockets.
● Apache web proxy config had to be fixed to allow websockets to work
● Thanks to Zachary Ware, the ops team member who did the work!

Mission Accomplished!
● Zachary Ware, flipped the switch in October 2017
● http://buildbot.python.org/all/

Thanks
● Zachary Ware, who helped on the ops side and did the final work
● Pierre Tardy, Buildbot maintainer who reviewed and merged my Py3
patches
● Twisted developers: Glyph Lefkowitz, Amber Brown, Adi Roiban, Abishek
Choudhary who helped review my Twisted Py3 patches

Contact me
● Craig Rodrigues <rodrigc@crodrigues.org>
Linkedin: https://linkedin.com/in/rodrigc
Twitter: @rodrigc6

Migrating python.org to buildbot 9 and python 3

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