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Date: Thu, 7 May 2015 08:53:37 -0500
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Subject: Re: Staging Branches
From: Josh McKenzie <josh.mckenzie@datastax.com>
To: dev@cassandra.apache.org
Cc: Gary Dusbabek <gdusbabek@gmail.com>
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>
> I still think this is overly complicated. We still
> need to run CI before we release. So what does this buy us?


I second this line of questioning. This sounds like we have a solution
looking for a problem; we're not talking about people git cloning our repo
and running it in production.

On Thu, May 7, 2015 at 8:48 AM, Jake Luciani <jakers@gmail.com> wrote:

> git rebase -i trunk_staging <ref~1>
> fix the problem
> git rebase --continue
>
> In this situation, if there was an untested follow on commit wouldn't
> you need to force push?
>
> On Thu, May 7, 2015 at 9:28 AM, Benedict Elliott Smith
> <belliottsmith@datastax.com> wrote:
> >>
> >> If we do it, we'll end up in weird situations which will be annoying for
> >> everyone
> >
> >
> > Such as? I'm not disputing, but if we're to assess the relative
> > strengths/weaknesses, we need to have specifics to discuss.
> >
> > If we do go with this suggestion, we will most likely want to enable a
> > shared git rerere cache, so that rebasing is not painful when there are
> > future commits.
> >
> > If instead we go with "repairing" commits, we cannot have a "queue" of
> > things to merge up to. Say you have a string of commits waiting for
> > approval C1 to C4; you made C1, and it broke something. You introduce C5
> to
> > fix it, but the tests are still broken. Did you not really fix it? Or
> > perhaps one of C2 to C4 are to blame, but which? And have you
> accidentally
> > broken *them* with your commit? Who knows. Either way, we definitely
> cannot
> > fast forward. At the very best we can hope that the new merge did not
> > conflict or mess up the other people's C2 to C4 commits, and they have to
> > now merge on top. But what if another merge comes in, C6, in the
> meantime;
> > and C2 really did also break the tests in some way; how do we determine
> C2
> > was to blame, and not C6, or C3 or C4? What do the committers for each of
> > these do? We end up in a lengthy tussle, and aren't able to commit any of
> > these to the mainline until all of them are resolved. Really we have to
> > prevent any merges to the staging repository until the mistakes are
> fixed.
> > Since our races in these scenario are the length of time taken for cassci
> > to vet them, these problems are much more likely than current race to
> > commit.
> >
> > In the scheme I propose, in this scenario, the person who broke the build
> > rebases everyone's branches to his now fixed commit, and the next broken
> > commit gets blamed, and all other commits being merged in on top can go
> in
> > smoothly. The only pain point I can think of is the multi-branch rebase,
> > but this is solved by git rerere.
> >
> > I agree running tests is painful, but at least for the build, this should
> >> be the responsibility of the committer to build before merging
> >
> >
> > Why make the distinction if we're going to have staging commits? It's a
> bit
> > of a waste of time to run three ant real-clean && ant tasks, and
> increases
> > the race window for merging (which is painful whether or not involves a
> > rebase), and it is not a *typical* occurrence ("alarming" is subjective)
> >
> > On Thu, May 7, 2015 at 2:12 PM, Sylvain Lebresne <sylvain@datastax.com>
> > wrote:
> >
> >> > If one of them breaks, we go and edit the _staging branch in place to
> >> correct
> >> > the problem, and let CI run again.
> >>
> >> I would strongly advise against *in place* edits. If we do it, we'll
> end up
> >> in
> >> weird situations which will be annoying for everyone. Editing commits
> that
> >> have
> >> been shared is almost always a bad idea and that's especially true for
> >> branch
> >> that will have some amount of concurrency like those staging branches.
> >>
> >> Even if such problems are rare, better to avoid them in the first place
> by
> >> simply
> >> commit new "fixup" commits as we currently do. Granted this give you a
> >> slightly
> >> less clean history but to the best of my knowledge, this hasn't been a
> pain
> >> point so far.
> >>
> >> > wait for CI; all clear
> >> >
> >> > git checkout cassandra-2.0; git merge cassandra-2.0_staging
> >> > git checkout cassandra-2.1; git merge cassandra-2.1_staging
> >> > git checkout trunk; git merge trunk_staging
> >> >
> >> > This does introduce some extra steps to the merge process
> >>
> >> If we do this, we should really automate that last part (have the CI
> >> environment merge the staging branch to the non-staging ones on
> success).
> >>
> >> > It seems if we want an "always releasable" set of branches, we need
> >> something
> >> > along these lines.
> >>
> >> Agreed as far as having staging branches vetoed by CI goes. Less sure
> about
> >> the edit-commit-in-place part as said above.
> >>
> >> > I certainly break tests by mistake, or the build itself, with alarming
> >> regularity.
> >>
> >> I agree running tests is painful, but at least for the build, this
> should
> >> be
> >> the responsibility of the committer to build before merging. We all
> forget
> >> it from
> >> times to times and that's ok, but it's not ok if it's "alarmingly
> regular".
> >>
> >> --
> >> Sylvain
> >>
>
>
>
> --
> http://twitter.com/tjake
>


-- 
Joshua McKenzie
DataStax -- The Apache Cassandra Company

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