Re: bug#47897: [PATCH] substitutes: Don't cache negative lookups or transient errors.

[Christopher Baines <mail@cbaines.net>]

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Ludovic Courtès <ludo@gnu.org> writes:

> Hi,
>
> Christopher Baines <mail@cbaines.net> skribis:
>
>>> Now, the penalty it imposes is annoying.  I’ve sometimes found myself
>>> working around it, too (because I knew the server was going to have the
>>> store item sooner than 1h).
>>>
>>> Rather than removing it entirely, I can think of these options:
>>>
>>>   1. Reduce the default negative timeouts.
>>
>> I think reducing it is good, as you say, it's possible to override the
>> default from the server side. Just in case someone wants caching
>> behaviour, it might be worth keeping that functionality at least.
>
> OK, let’s do that.
>
>>>   2. Add an option to ‘guix publish’ (and to the Coordinator?) so they
>>>      send a ‘Cache-Control’ header with the chosen TTL on 404.  That
>>>      way, if the server operator doesn’t mind extra load, they can run
>>>      “guix publish --negative-ttl=0”.
>>
>> That sounds sensible. The Guix Build Coordinator doesn't do any serving,
>> that's left to something else like nginx. For the deployments I maintain
>> though, I don't think I'm setting the relevant headers, but I'll look at
>> changing that.
>
> Cool.
>
>> Going back to the %narinfo-transient-error-ttl, if I'm correct in saying
>> that it's not possible to override that, maybe that should also use the
>> relevant header value if set?
>
> Correct, ‘%narinfo-transient-error-ttl’ cannot be overridden.  We can
> halve it if you think that’s useful, thought when that happens, it means
> something’s wrong with the server (returning 500 or similar).
>
> I’ve sent patches to address this, lemme know what you think!

The patches you've sent look good.

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