I’ve been noticing a trend where there is more and more false positive email notifications sent out on valid commits. This is getting really problematic as real signal is being lost in the noise. I’ve had several cases in the last few weeks where I did not see a “real” failure notice because it was buried in a bunch of false positives.
Let me run through a few sources of what I consider false positives, and suggest a couple things we could do to clean these up. Note that the recommendations here are entirely independent and we can adopt any subset.
Slow Try Bots
ex: “This revision was landed with ongoing or failed builds.” on
Someone - I’m not really sure who - enabled builds for all reviews, and this notice on landed commits. Given it’s utterly routine to make a last few style fixes before landing an LGTMed change, I consider this notice complete noise. In practice, almost review gets tagged this way. To be clear, there is value in being told about changes which don’t build. The false positive part is only around the “ongoing” builds.
Recommendation: Disable this message for the “ongoing” build case, and if we can’t, disable them entirely.
Flaky Builders
ex:
We have many build bots which are not entirely stable. It’s gotten to the point where I expect failure notifications on literally every change I land. I’ve been trying to reach out to individual build bot owners to get issues resolved, and to their credit, most owners have been very responsive. However, we have enough builders that the situation isn’t getting meaningful better.
Recommendation: Introduce specific “test commits” whose only purpose is to run the CI infrastructure. Any builder which notifies of failure on such a commit (and only said commit) is disabled without discussion until human action is taken by the bot owner to re-enable. The idea here is to a) automate the process, and b) shift the responsibility of action to the bot owner for any flaky bot.
Note: By “disabled”, I specifically mean that notification is disabled. Leaving it in the waterfall view is fine, as long as we’re not sending out email about it.
Aside: It’s really tempting to attempt to separate builders which are “still failing” (e.g. a rare configuration which has been broken for a few days) from “flaky” ones. I’d argue any bot notifying on a “still failing” case is buggy, and thus it’s fine to treat them the same as a “flaky” bot.
Slow Builders and Redundant Notices
ex:
Occasionally, we have a bad commit land which breaks every (or nearly every) builder. That happens. If you happen to land a change just before or after it, you then get on the blame list for every slow running builder we have (since they tend to have large commit windows) if they happen to cycle before the fix is committed. This is particularly annoying since the root issue is likely fixed quickly, but due to cycle times on the builders, you may be getting emails for 24 hours to come.
Recommendation: Introduce a new requirement for “slow” builders (say cycle time of > 30 minutes) either a) have a maximum commit window of ~15 commits, or b) use a staged builder model. Personally, I’d prefer the staged model, but the max commit window at least helps to limit the damage.
By “staged builder model”, I mean that slow builders only build points in the history which have already been successfully build by one of the fast builders. This eliminates redundant build failures, at the cost of delaying the slow builder slightly. As long as the slow builder uses the “last good commit” as opposed to waiting until the current fast builder finishes, the delay should be very minimal for most commits.
Philip