GNU bug report logs - #30290
guix-daemon slows to a crawl when a substitute server is offline

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From: help-debbugs <at> gnu.org (GNU bug Tracking System)
To: Maxim Cournoyer <maxim.cournoyer <at> gmail.com>
Cc: tracker <at> debbugs.gnu.org
Subject: bug#30290: closed (guix-daemon slows to a crawl when a substitute
 server is offline)
Date: Mon, 10 Oct 2022 03:04:01 +0000

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Your message dated Sun, 09 Oct 2022 23:03:16 -0400
with message-id <87zge42xe3.fsf <at> gmail.com>
and subject line Re: bug#30290: guix-daemon slows to a crawl when a substitute server is offline
has caused the debbugs.gnu.org bug report #30290,
regarding guix-daemon slows to a crawl when a substitute server is offline
to be marked as done.

(If you believe you have received this mail in error, please contact
help-debbugs <at> gnu.org.)


-- 
30290: https://debbugs.gnu.org/cgi/bugreport.cgi?bug=30290
GNU Bug Tracking System
Contact help-debbugs <at> gnu.org with problems

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From: Maxim Cournoyer <maxim.cournoyer <at> gmail.com>
To: bug-guix <bug-guix <at> gnu.org>
Subject: guix-daemon slows to a crawl when a substitute server is offline
Date: Mon, 29 Jan 2018 22:07:49 -0500

When a substitute server used by guix-daemon is offline, the daemon will
keep attempting to connect to it, even when it shouldn't need any data
(ran 'sudo guix system reconfigure my-config.scm' multiple times in a
row.

With the disconnected server (bayfront in my case), that command would
take close to 8 minutes, with many system calls like:

--8<---------------cut here---------------start------------->8---
connect(14, {sa_family=AF_INET, sin_port=htons(443), sin_addr=inet_addr("141.255.128.56")}, 16) = -1 EINPROGRESS
--8<---------------cut here---------------end--------------->8---

which wasted 5 seconds each time.

After removing this server from my substitute servers list, the same
operation (system reconfigure) is 8 times faster (1 minute).

Suggestion: the daemon should stop trying to use the offline substitute
server after trying for X times, and print a warning about it.

Maxim

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From: Maxim Cournoyer <maxim.cournoyer <at> gmail.com>
To: zimoun <zimon.toutoune <at> gmail.com>
Cc: Mathieu Othacehe <othacehe <at> gnu.org>, ludo <at> gnu.org,
 30290-done <at> debbugs.gnu.org
Subject: Re: bug#30290: guix-daemon slows to a crawl when a substitute
 server is offline
Date: Sun, 09 Oct 2022 23:03:16 -0400

Hi Simon,

zimoun <zimon.toutoune <at> gmail.com> writes:

> Hi Maxim,
>
> On Wed, 23 Mar 2022 at 11:50, zimoun <zimon.toutoune <at> gmail.com> wrote:
>> On Wed, 18 Aug 2021 at 22:25, Maxim Cournoyer <maxim.cournoyer <at> gmail.com> wrote:
>
>>> Extra note: the problems reported earlier (hang or backtrace instead of
>>> graceful fallback to other substitute servers) also affect the scenario
>>> where substitutes are fetched from uDNS discovered substitute servers (I
>>> just tried).
>>
>> I guess this old bug [1] about the daemon hanging is still there, right?
>>
>> How such issue could be tackled?
>>
>> 1: <http://issues.guix.gnu.org/issue/30290>
>
> What could be actionable for tackling this old bug?

I can't seem to reproduce the original issue, which was that an offline
server would slow down fetching of substitutes by repeatedly trying to
reach it, at least when setting e.g.:

--8<---------------cut here---------------start------------->8---
127.0.0.2 ci.guix.gnu.org
--8<---------------cut here---------------end--------------->8---

In my /etc/hosts file to simulate it's unreachable, with at least
another substitute server available in my --substitute-urls list.  It
goes right to that second server without loosing any time.

Closing for now, we can always reopen the issue if it manifests itself
in the future.

-- 
Thanks,
Maxim

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