Tuesday, May 17, 2011

Assisted/Automated Landing - Designing the Systems

Ehsan's blog post wishing for assisted landings on mozilla-central started a lot of people talking about this being a very desirable and useful tool for developers, where they could set a flag in Bugzilla and then be free to do other work until the results of their push were posted back to the bug. As part of enhancing the Tryserver I was already working on a way for users to signify in their try-syntax that the results of the push should go to the bug and these two ideas started to fuse into a dreamworld where someone could attach a patch to Bugzilla and have it be tried and pushed to trunk all with some magical bot automation.

After doing a very short survey of developers and their try usage I have observed that there are two very different stakeholders here and both of them need separate-but-related tools:

DevelopersThe Bot (automation)
  • ease of use
  • better reporting (less email anyone?)
  • option to post to bug(s) *after* a try run has indicated success
  • queuing of patches culled from a flag in Bugzilla
  • automatically apply to tip of repo
  • push, and report back with results

After soaking in the survey feedback and a first attempt with a whiteboard yesterday, I woke up this morning with some clearer ideas on how to take a first run at creating this system.  It involves creating several new tools, one new database, and enhancing our existing buildapi.

New tools for Developers:
  • Adding more Try syntax options:
    • include list of the bug(s) that you would like your try results posted to (however many make for a complete run on your push, this can be one linux build or a complete ~186 builder try: -a buildset) 
    • turn off email notifications
  • Adding functionality to the self-serve api view for a revision (eg: https://build.mozilla.org/buildapi/self-serve/try/rev/de8ea75bc48e) that will better show your results for that push and provide a button which will post the patch(es) to a specified bug
  • Auto-landing from a bug in Bugzilla using the [autoland-try] whiteboard tag where any attached patches which are not obsolete, and have nothing set for 'r' are applied to the current tip of mozilla-central, pushed to try and those results are returned to a comment in the bug
New tools to Automate landings (bot or script):
  • Crawl Bugzilla for bugs where [autoland-$branchname] is in the whiteboard and automatically push to tip of named branch, get the results, and return them to a comment in the bug (stripping out the whiteboard tag on completion)
    • bot will grab all non-obsolete, r+ patches (if $branchname != 'try') 
    • interdependent bugs will not be handled in this first swipe at a working system
    • pushes will have autoland-$bugnumber as the reason for the build in schedulerdb so that the results can be watched for, aggregated, and reposted to the bug on completion
  • Watch results coming back for one or two oranges (we can set a threshold) and re-triggers those, watching for the second set of results - to attempt catching intermittent oranges
  • Backout patches where even with a rebuild on an orange, there still remain orange results
  • LDAP authentication checking for bugzilla patch author -> hg commit permissions and being able to ensure that only people with the right credentials can trigger automatic landings. This may mean checking the reviewer too before allowing a patch to be applied & pushed.
The next step is to get this design organized into bugs so that we can parcel out the work involved and start testing/completing segments and features as we work towards the whole. We have a RelEng intern this summer, Marc Jessome (Another Canadian in RelEng!), who will be doing a lot of the work between now and the end of August. Stop by anytime to say "Hi" to Marc and to chat with either of us about the project - feedback is always appreciated.  I'm happy to say that 52 people filled out the Try Usage survey just from posting it on Yammer. That was super helpful, thank you.

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