[webkit-dev] Please avoid rolling out patches speculatively and reland them ASAP if you had to

Ryosuke Niwa rniwa at webkit.org
Tue Dec 11 14:33:46 PST 2012

On Tue, Dec 11, 2012 at 2:17 PM, Peter Kasting <pkasting at chromium.org>wrote:

> On Tue, Dec 11, 2012 at 2:14 PM, Oliver Hunt <oliver at apple.com> wrote:
>> I don't understand why anyone is _speculatively_ rolling out patches.
>> You should only be rolling it out if you _know_ the patch is bad.
> Sometimes something bad happens to the tree, the sheriff doesn't know
> which patch is responsible, and the change authors are not present to ask
> for help.  In a case like this the sheriff has to either do speculative
> rollouts or leave the tree broken.


Ideally, of course, change authors are around when something like this
> happens.  But maybe the bustage doesn't happen until much later, due to
> some subtle/latent issue, or maybe the change author is in fact
> irresponsible.

Given that some bots take 4-5 hours to cycle these days, it's hard to keep
eyes on all bots all the time. So things like this would happen.

Having said that, a *speculative *roll out should one's last report.
Rolling out a patch causes a lot of svn churn, increases bot cycle time,
etc... and should be avoided if the failure can be fixed easily.
Furthermore, it's often not too hard to test a rollout locally to see if it
actually fixes the problem as Oliver suggested.


In general, I feel that some people are too religious about keeping bots
green and too eager to roll out patches without trying to fix the failures
or even understanding the failures and are actively harmful to the project.

The main goal of continus build & test systems should be to help the
development of WebKit, not to run them for the sake of keeping them green.

- R. Niwa
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