[syslog-ng] Syslog-ng appears to hang for local requests to log

[Balazs Scheidler]

On Mon, 2007-08-06 at 11:56 +1200, Russell Fulton wrote:
> 
> Paul Robert Marino wrote:
> > I just joined the list after seeing in the archive the syslog-ng
> > causing other proccesses to freeze
> > I've seen the same issue in syslog-ng-2.0.2. I also usualy see some
> > error about exciding the maximum number of open files for root. if i
> > happen to be loged in to the box as root I've been able to fix it by
> > restarting syslog-ng. if ive been loged in as my normal useri can
> > usualy run a sudo lsof but when i count the number of open files its
> > onwhere near the number set in /etc/secutiy/limits.conf. i also
> > ocasionaly see this in the logs right before it happens
> I'm now pretty sure that my problems are not related to file handles --
> syslog-ng seems to have a builtin limit of 1024 open file handles  and
> nev er goes over according to lsof.
> 
> I have just upgraded to 2.0.5 but another thing has just occurred to
> me.  I have a destination fifo which is used intermittently.  Fifo has
> an 8KB buffer and I just wondered what happens when this fills.  Do
> writes from syslog-ng fail? If so does syslog-ng then try and buffer
> output itself?  If so that would explain what we are seeing.
> 
> If the new version does not fix the issue I will try disabling the fifo
> destination.

It depends on the flow-control setting of the log-path with the fifo
destination.

If flow-control is enabled and the fifo is not read, then the input side
of syslog-ng will be suspended, thus the applications trying to send
messages will be blocked.

That's how flow-control behaves. See the chapter on flow-control in the
manual.

-- 
Bazsi