[ovirt-devel] Gerrit parallel patch handling and CI (Or, why did my code fail post-merge)

[Sandro Bonazzola]

Il 20/Nov/2016 15:08, "Barak Korren" <bkorren at redhat.com> ha scritto:
>
> Hi there,
>
> I would like to address a concernt that had been raised to us by
> multiple developers, and reach an agreement on how (and if)  to remedy
> it.
>
> Lets assume the following situation:
> We have a Git repo in Gerrit with top commit C0 in master.
> On time t0 developers Alice and Bob push patches P1 and P2 respectively
> to master so that we end up with the following situation in git:
> C0 <= P1 (this is Alice`s patch)
> C0 <= P2 (this is Bob`s patch)
>
> On time t1 CI runs for both patches checking the code as it looks for
> each patch. Lets assume CI is successful for both.
>
> On time t2 Alice submits her patch and Gerrit merges it, resulting in
> the following situation in master:
> C0 <= P1
>
> On time t2 Bob submits his patch. Gerrit, seeing master has changed,
> re-bases the patch and merges it, the resulting situation (If the
> rebase is successful) is:
> C0 <= P1 <= P2
>
> This means that the resulting code was never tested in CI. This, in
> turn, causes various failures to show up post-merge despite having
> pre-merge CI run successfully.
>
> This situation is a result of the way our repos are currently
> configured. Most repos ATM are configured with the "Rebase If
> Necessary" submit type. This means that Gerrit tries to automatically
> rebase patches as mentioned in t2 above.
>
> We could, instead, configure the repos to use the "Fast Forward Only"
> submit type. In that case, when Bob submits on t2, Gerrit refuses to
> merge and asks Bob to rebase (While offering a convenient button to do
> it). When he does, a new patch set gets pushed, and subsequently
> checked by CI.
>
> I recommend we switch all projects to use the "Fast Forward Only" submit
type.
>
> Thoughts? Concerns?

+1 for me

>
> --
> Barak Korren
> bkorren at redhat.com
> RHEV-CI Team
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