Yes, you can do this. See http://www.balabit.com/sites/default/files/documents/syslog-ng-ose-3.2-guides/syslog-ng-ose-v3.2-guide-admin-en.html/index.html-single.html#chapter-log-statistics
Note the bit about sending "STATS" to the syslog control socket. Look for the "stored" lines, these are what youre after. (can use `nc -U` instead of socat as well)

You could also use the stats on the server and alert when the source counter stops incrementing.

-Patrick


Sent: Fri Nov 18 2011 18:54:13 GMT-0700 (MST)
From: Paul Muther <dalamars@gmail.com>
To: syslog-ng@lists.balabit.hu
Subject: [syslog-ng] Monitoring syslog-ng logserver 
Greetings all,

I have a question about monitoring syslog-ng itself.  In the event that the log server stops listening or stops processing for messages for whatever reason is there a way to alert on hosts that messages are being queued/buffered?  

In a situation recently the log server syslog-ng process was running but not accepting log messages from remote hosts for some reason.  As a result they all pilled up at the sources until the clients rolled over.  It would be helpful to have an alert that it is happening but I can't find anything on monitoring the buffers.  

Thanks much,
PM

______________________________________________________________________________
Member info: https://lists.balabit.hu/mailman/listinfo/syslog-ng
Documentation: http://www.balabit.com/support/documentation/?product=syslog-ng
FAQ: http://www.balabit.com/wiki/syslog-ng-faq