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From:   Junio C Hamano <gitster@pobox.com>
To:     Johannes Schindelin <Johannes.Schindelin@gmx.de>
Cc:     git@vger.kernel.org, rsbecker@nexbridge.com,
        'Jeff King' <peff@peff.net>, 'Taylor Blau' <me@ttaylorr.com>,
        'Andy Koppe' <andy.koppe@gmail.com>
Subject: Re: [PATCH] ci: avoid building from the same commit in parallel
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Date:   Wed, 23 Aug 2023 09:08:07 -0700
In-Reply-To: <1da763f3-60bf-a572-2c71-336b1fa5553d@gmx.de> (Johannes
        Schindelin's message of "Wed, 23 Aug 2023 10:42:45 +0200 (CEST)")
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Johannes Schindelin <Johannes.Schindelin@gmx.de> writes:

> Hi Junio,
>
> On Tue, 22 Aug 2023, Junio C Hamano wrote:
>
>> Johannes Schindelin <Johannes.Schindelin@gmx.de> writes:
>>
>> > Right, we'd need that `concurrency: ${{ github.sha }}` attribute on
>> > the `config` job.
>>
>> That was my first thought, but I am not sure how it would work.
>>
>> Doesn't skip-if-redundant grab the workflow runs that have succeeded
>> and then see if one for the same commit already exists?  If you used
>> concurrency on the 'config', what gets serialized between two jobs
>> for the same commit is only the 'config' phase, so 'master' may wait
>> starting (because 'config' is what everybody else 'needs' it) while
>> 'config' phase of 'main' runs, and then when it gets to the turn of
>> 'config' phase of 'master', it would not find the run for the same
>> commit being done for 'main' completed yet, would it?
>
> Yes, that's true.
>
> But there is a silver lining: the `concurrency` can not only be specified
> on the job level, but also on the workflow run level.
> I tested this, and present the corresponding patch at the end of this
> mail.

Yeah, serializing the whole thing was the only way I thought that
would work, and I am glad you already tested that it works.

Thanks.