Rampant Nagios

[Andreas Ericsson]

McCann, Brian wrote:
> I have the same thing, sometimes it even will stop doing checks and I
> have to kill the Nagios process and start over again...happens every 2-4
> days.  Sometimes it is a CPU hog, othertimes it's just non-responsive.
> I'm on FreeBSD 5.3-REALEASE-p5.  I've yet to find a workaround for this
> sadly.
> 

This is due to pthread locks being poorly implemented on FreeBSD where 
it's possible for an application to deadlock. The CPU-hog part is most 
likely from when this happens on a spin-lock.

Spinlocks (for those interested) are implemented something like this
while(1) if(spinlock == SPINLOCK_UNLOCKED) break;
and naturally eats as much CPU as it can get. There might be a 10 to 
50usec sleep or something in there, but the gist of it is an endless 
loop which awaits actions from some other process before it can continue.

Stanley Hopcroft reported a couple of days ago that FreeBSD 4.11 (or 
some such) was unaffected by this bug and therefore much better suited 
to running multithreaded applications.

> --Brian 
> 
> -----Original Message-----
> From: nagios-users-admin at lists.sourceforge.net
> [mailto:nagios-users-admin at lists.sourceforge.net] On Behalf Of
> admin at jpk236.com
> Sent: Tuesday, May 17, 2005 0:40
> To: nagios-users at lists.sourceforge.net
> Subject: [Nagios-users] Rampant Nagios
> 
> Nagios v2.03b3
> FreeBSD 5.4-RELEASE-p1
> 
> On some of the hosts I monitor I've been noticing some peculiarities.
> Nagios will spontaneously become a CPU hog -- using an upwards of 80-90%
> CPU, sometimes higher.
> 
> I try stopping nagios using FreeBSD's rc.d script for nagios.  The
> output claims nagios has stopped, but when I run `ps auxwww` there is
> still an instance of nagios running.  I can only assume the rc.d script
> was able to remove the lock file, but was not able to stop the process.
> 
> Has anyone else experienced this behavior?
> 
>   - Justin Kulikowski
> 	[ http://www.jpk236.com ]
> 
> 
> 
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-- 
Andreas Ericsson                   andreas.ericsson at op5.se
OP5 AB                             www.op5.se
Lead Developer


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