Re: [PATCH] gc: do not warn about too many loose objects

From: Jonathan Nieder <jrnieder@gmail.com>
Date: Jul 16, 2018, 19:09 UTC
Message-ID: <20180716190949.GB11513@aiede.svl.corp.google.com>
In-Reply-To: <20180716185255.GC22298@sigill.intra.peff.net>

Hi,

Jeff King wrote:

> On Mon, Jul 16, 2018 at 11:22:07AM -0700, Jonathan Nieder wrote:
>> Jeff King wrote:

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>>> So while I completely agree that it's not a great thing to encourage
>>> users to blindly run "git prune", I think it _is_ actionable.
>>
>> To flesh this out a little more: what user action do you suggest?  Could
>> we carry out that action automatically?
>
> Er, the action is to run "git prune", like the warning says. :)

I don't think we want to recommend that, especially when "git gc --auto" does the right thing automatically.

Can you convince me I'm wrong?

[...]

>> I mentally make a distinction between this warning from "git gc
>> --auto" and the warning from commands like "git gui".

[...]

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> I don't think those warnings are the same. The warning from "git gui"
> is: you may benefit from running gc.
>
> The warning that is deleted by this patch is: you _just_ ran gc, and hey
> we even did it automatically for you, but we're still in a funky state
> afterwards. You might need to clean up this state.

This sounds awful. It sounds to me like you're saying "git gc --auto" is saying "I just did the wrong thing, and here is how you can clean up after me". That's not how I want a program to behave.

But there's a simpler explanation for what "git gc --auto" was trying to say, which Jonathan described.

[...]

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>> Yes, this is a real problem, and it would affect any other warning
>> (or even GIT_TRACE=1 output) produced by gc --auto as well.  I think we
>> should consider it a serious bug, separate from the symptom Jonathan is
>> fixing.
>>
>> Unfortunately I don't have a great idea about how to fix it.  Should
>> we avoid writing warnings to gc.log in daemon mode?  That would
>> prevent the user from ever seeing the warnings, but because of the
>> nature of a warning, that might be reasonable.
>
> If you do that without anything further, then it will break the
> protection against repeatedly running auto-gc, as I described in the
> previous email.

Do you mean ratelimiting for the message, or do you actually mean repeatedly running auto-gc itself?

If we suppress warnings, there would still be a gc.log while "git gc --auto" is running, just as though there had been no warnings at all. I believe this is close to the intended behavior; it's the same as what you'd get without daemon mode, except that you lose the warning.

[...]

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>> Should we put warnings
>> in a separate log file with different semantics?  Should we change the
>> format of gc.log to allow more structured information (include 'gc'
>> exit code) and perform a two-stage migration to the new format (first
>> learn to read the new format, then switch to writing it)?
>
> Any of those would work similarly to the "just detect warnings" I
> suggested earlier, with respect to keeping the "1 day" expiration
> intact, so I'd be OK with them. In theory they'd be more robust than
> scraping the "warning:" prefix. But in practice, I think you have to
> resort to scraping anyway, if you are interested in treating warnings
> from sub-processes the same way.

Can you say more about this for me? I am not understanding what you're saying necessitates scraping the output. I would strongly prefer to avoid scraping the output.

Thanks, Jonathan