Release Automation – Part 2: Mercurial-based, v1

Around the start of 2008 Mozilla moved Firefox and Gecko development from CVS to Mercurial, with Firefox 3.5 (nee 3.1) as the first release out of the new repository. In addition to that, the underlying build infrastructure had switched from being Tinderbox driven, to being Buildbot driven – which made some of the existing release automation useless. In mid-2008 we started planning to port, rework, and update the release automation for this new environment. The 2008 Firefox Summit conveniently happened right around this time, so we took that opportunity to gather a quorum on the subject and go over all the plans in detail. By the end of the night (and end of the beer, if I recall correctly), we had discussed everything to death a tracking bug.

This version of the automation struck a balance between improving the overall design of the system and simply doing straight porting work. The plain porting isn’t very interesting, so I’ll be mostly focusing on the improvements we made in this post.

One of the bigger optimizations we made to to generate files in their final location at build time. In the Bootstrap days we uploaded files to flat directories with long filenames, and then re-arranged them into their final layout later on in the process. With this change made our candidates directories looked a lot more like the the associated release directory. This may not sound like a huge change but it cut our disk space usage per release in half or more, shaved over an hour off the end2end time of the release, and let us put our release file naming logic into the build system, where it more rightly belonged. It also allowed us to make the next optimization: combining the signing processes.

In the Bootstrap and pre-Bootstrap worlds we had two separate signing processes: one to sign the internal guts of Firefox win32 builds (firefox.exe, xul.dll, et. al) and one to sign the Firefox installers themselves. Early on, we signed the internal bits and handed them off to QA. Closer to release time, we signed the installers themselves and generated GPG signatures for all files. The only reason I can think of why we would do this is to keep signed installers out of public directories until we’re sure we’ll be releasing them. This isn’t without its drawbacks though. Leaving this until later in the process added unnecessary manual touchpoints, put non-trivial work late in the critical path, and worst of all: It meant QA did not test the exact bits that we shipped to users! (We actually managed to ship unsigned installers once, which isn’t possible anymore.) Improving this only required a small rework of our existing signing scripts (and lots of testing, of course!) but it took another 1-2h off of our end2end time and removed another manual touchpoint.

It’s also worth noting that merely by switching to Mercurial we saved over half an hour in end2end time in tagging. In CVS, we had to create a branch and tag thousands and thousands of files with multiple tags, which takes a very long time. In Mercurial, we have clone a repository, which takes some time, but the tagging itself is near-instant.

In addition to the optimizations noted above, tons of work was done porting the existing automation. Many things had to be pulled out of Bootstrap and put into their own scripts to make them usable by both versions of the automation; en-US builds and l10n repacks had to be reimplemented entirely in Buildbot; and some other things that couldn’t be pulled out of Bootstrap had to be reimplemented as well. It was a very large undertaking that was primarily worked on by Nick Thomas, Coop, and myself and took months to complete.

Firefox 3.1b3 was the first fully automated release with this automation. By the time we worked out most of the kinks we were at end2end time of 8-10h and about 12 manual touchpoints.

Next up: Various improvements & optimizations (not as boring as it sounds, I promise!)

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