From: Jan Braun <janbraun@gmx.de>
To: "Carl Winbäck" <c@tunnel53.net>
Cc: supervision@list.skarnet.org
Subject: Re: Logging in a web server context
Date: Sat, 13 Jun 2020 12:59:42 +0200 [thread overview]
Message-ID: <20200613105942.GA21613@klumpi.ignorelist.com> (raw)
In-Reply-To: <CACsCw1MhwhCcq=_VJn5N+On0=5B5oWFV6nK0FuvfUFSEKxGoJg@mail.gmail.com>
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Hey,
Carl Winbäck schrob:
> Is it possible when using s6-svscan/s6-supervise to somehow arrange so
> that a daemon’s stdout is sent to one logdir and stderr to another
> logdir?
I'm not completely sure about s6, but runsv (from runit) hands only the
stdout of the ./run script to the logger, and passes the stderr out of
it's own stderr. This allows you to nest two runsv instances, one for
each output channel:
$ find -type f | xargs head -n 99
==> ./inner/log/run <==
#!/bin/sh
mkdir -p stdout
svlogd -t stdout
==> ./inner/run <==
#!/bin/sh
echo stderr >&2
echo stdout
sleep 10
==> ./log/run <==
#!/bin/sh
mkdir -p stderr
svlogd -t stderr
==> ./run <==
#!/bin/sh
exec runsv inner 2>&1
$ timeout 11 runsv .
$ find -name current | xargs head
==> ./inner/log/stdout/current <==
@400000005ee4a23f2591745c stdout
@400000005ee4a24925b79614 stdout
==> ./log/stderr/current <==
@400000005ee4a23f257ae304 stderr
@400000005ee4a24925b76f04 stderr
$
Translation to s6 is left as an exercise to the reader.
> One tricky aspect of logging that is specific to web servers is that
> they emit two different categories of messages:
>
> a) Errors and warnings
>
> b) Info about page requests[2]
You could also run the webserver with stderr redirected to stdout, and
let s6-log/svlogd filter the messages into one of two logdirs:
$ printf 'stdout\nstderr\n' | s6-log -- '-.*err' t ./stdout f t ./stderr
$ head std*/current
==> stderr/current <==
@400000005ee4acd00efdfbe9 stderr
==> stdout/current <==
@400000005ee4acd00efd6f5e stdout
However, that's a brittle solution, because it relies on you creating
correctly-matching filter rules. Depending on the webserver's output, it
might still be feasible, but I recommend the other approach.
HTH & cheers,
Jan
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next prev parent reply other threads:[~2020-06-13 10:59 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-06-13 8:41 Carl Winbäck
2020-06-13 10:04 ` Casper Ti. Vector
2020-06-13 10:50 ` Carl Winbäck
2020-06-13 11:32 ` Casper Ti. Vector
2020-06-13 12:40 ` Carl Winbäck
2020-06-13 10:59 ` Jan Braun [this message]
2020-06-13 11:17 ` Carl Winbäck
2020-06-13 12:42 ` Laurent Bercot
2020-06-13 12:53 ` Laurent Bercot
2020-06-14 12:06 ` Carl Winbäck
2020-06-14 12:02 ` Carl Winbäck
[not found] ` <20200613100522.jvixsd6fnokz3fh2@bstg>
2020-06-13 12:17 ` Carl Winbäck
2020-06-13 12:30 ` Carl Winbäck
2020-06-13 18:51 ` Steve Litt
2020-06-13 19:29 ` yianiris
2020-06-15 4:19 ` Colin Booth
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