On 4/26/2013 12:17 PM, Ryan VanderMeulen wrote:
> Specific goals:
> -Offer an alternative branch for developers to push to during extended
> inbound closures
> -Avoid patch pile-up after inbound re-opens from a long closure
>
> Specific non-goals:
> -Reducing infrastructure load
> -Changing pushing strategies from the widely-accepted status quo (i.e.
> multi-headed approach)
> -Creating multiple integration branches that allow for simultaneous
> pushing (i.e. inbound-b2g, inbound-gfx, etc)
>
> My proposal:
> -Create an inbound2 branch identically configured to mozilla-inbound.
> -Under normal circumstances (i.e. m-i open), inbound2 will be CLOSED.
> -In the event of a long tree closure, the last green changeset from
> m-i will be merged to inbound2 and inbound2 will be opened for checkins.
> ---It will be a judgment call for sheriffs as to how long of a closure
> will suffice for opening inbound2.
> -When the bustage on m-i is resolved and it is again passing tests,
> inbound2 will be closed again.
> -When all pending jobs on inbound2 are completed, it will be merged to
> m-i.
> -Except under extraordinary circumstances, all merges to
> mozilla-central will continue to come from m-i ONLY.
> -If bustage lands on inbound2, then both trees will be closed until
> resolved. Tough. We apparently can't always have nice things.
If you consider that every repository is essentially a clone of
mozilla-central, what we have *now* is effectively equivalent to a
single repository with multiple heads/branches/bookmarks. However, the
different heads/branches/bookmarks differ in:
* How much attention sheriffs give them.
* The automation configuration (coalescing, priority, etc).
* Policies around landing.
* How developers use it.
These are all knobs in our control.
When we say "create an inbound2," we're essentially establishing a new
head/branch/bookmark that behaves much like "inbound1" with a slightly
different landing policy. If that's what we want to do, sure. I think
it's better than a single, frequently closed inbound.
Anyway, no matter how much I think about this proposal, I keep coming
back to the question of "why don't we use project branches more?"
Instead of everyone and her brother landing on inbound, what if more
landings were performed on {fx-team, services-central, <wood-named
twig>, etc}? I /think/ the worst that can happen is merge conflicts and
bit rot. And, we can abate that through intelligent grouping of related
commits in the same repository, frequent merges, and maybe even better
communication (perhaps even automatically with tools that alert
developers to potential conflicts - wouldn't it be cool if you updated a
patch and Mercurial was like "o hai - Ehsan recently pushed a Try push
that conflicts with your change: you two should talk.").
As a counter-proposal, I propose that we start shifting landings to
project branches/twigs. We should aim for a small and well-defined set
of repositories (say 3 to 5) sharing similar automation configuration
and sheriff love. By keeping the number small, it's easy to figure out
where something should land and it's not too much of an extra burden on
sheriffs. We can still keep inbound, but it should only be reserved for
major, cross-repository landings with multi-module impact (e.g. build
system changes), merges from the main landing repositories (unless we
merge straight to central), and possibly as a backup in case one of the
landing repositories is closed.
We can test this today with very little effort: we figure out how to
bucket commits, re-purpose existing repositories/twigs, and see what
happens. If it works: great - we've just validated that distributed
version control works for Firefox development (as opposed to the
CVS/Subversion workflow we're currently using with inbound). If not, we
can try variations and/or the inbound2 idea.
Is there sanity to this proposal or am I still crazy?
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