[systemd-devel] [PATCH] journald: check if socket is in connected state before forwarding to syslog

[Lennart Poettering]

On Fri, 11.07.14 09:52, Piotr Wilczek (p.wilczek at samsung.com) wrote:

> Currently syslog socket is not correctly verified if is in connected state.
> This results in sending messages to a socket that is not connected which is
> not allowed.
> 
> In this patch the socket is correctly checked. If the socket is not connected
> forwarding to syslog is disabled.
> 
> This patch causes about 15% decrease in CPU usage on Trats2 when ForwardToSyslog=yes
> but the syslog socket is not connected.

Not following here.

A) So, journald creates one listening AF_UNIX socket for syslog on
/run/systemd/journal/dev-log (which /dev/log is then symlinked
to). That's the socket you are checking. Which cannot really fail...

B) Now, as a shortcut we use the same sock actually, via sendto() to also
pass data to /run/systemd/journal/syslog, which is where a secondary
syslog server should listen on, which will then also receieve the
data. THis one is likely to fail, because journald starts very early,
and syslog daemons start very late, hence for the initial time no
message can be delivered at all. Moreover, in many setups there is no
secondary syslog, so this will fail each and every single time, but
that's intended really.

Now, your patch apparently looks for errors wth step A), and you argue
you want to get rid of CPU load of B), which I can't follow. Since A and
B are actually kinda separate they just happen to use the same socket,
because that was easier...

What I don't understand is why you need ForwardToSyslog= at all (which
turns off B)? I mean, does Samsung actually really run a second syslog?
If not, just set this to false.

In fact, we probably should turn this off by default now for everybody,
since rsyslog and friends nowadays get their data directly from the
journal, instead of using this socket...

Anyway, not following what you are trying to do! Please elaborate!

Lennart

-- 
Lennart Poettering, Red Hat