Re: Logging in a web server context

From: Carl Winbäck <>
Date: Sat, 13 Jun 2020 13:17:15 +0200

On Sat, 13 Jun 2020 at 12:59, Jan Braun <> wrote:
> 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:
> [...]
> Translation to s6 is left as an exercise to the reader.

Very interesting! I will study this example in depth in order to see
if it could be applied to s6.

If anyone has done this in s6, I would be interested to hear how you
achieved it.

> 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 <==
> _at_400000005ee4acd00efdfbe9 stderr
> ==> stdout/current <==
> _at_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.

I agree that this method is not rock-solid since it relies on text
parsing. But for my purposes it would probably be sufficient.

Then I have at least one solution that should be feasible and possibly
both of them are.

Thank you Jan!
Received on Sat Jun 13 2020 - 11:17:15 UTC

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