Hundreds of passive checks in a second

[Dan Stromberg]

If you use check_cluster2, then you can write a wrapper around check_tcp
or whatever, pass the exit statuses to check_cluster2 and hence
serialize your checks, while giving a single result back to nagios.  You
might have to increase the plugin timeout pretty high though.  It's
helpful to write the complete status description to a file on the head
node, so you can easily find out specifically what's wrong, once nagios
tells you Something is wrong.

Not precisely the same thing, but we had a similar problem with cron
jobs and NFS servers - we wound up writing a "rand_sleep" program, that
sleeps for a random number of seconds.  So we do rand_sleep 600 &&
/dir/cronjob.  I guess it's sort of similar.

On Fri, 2004-09-03 at 14:00, Sean Dilda wrote:
> I have a plugin that I'm running for a few hundred hosts that checks
> what SGE (Sun GridEngine) thinks the status of the node is.  The thing
> is, these checks don't hit the actual nodes.  Instead they all interact
> with the main SGE master daemon.  This means that all these checks and
> quickly run up the load if they're run close enough.
> 
> In order to keep from running the load up I was thinking about setting
> up a cron job that would do a single query against the SGE master daemon
> for all the hosts (only slightly more overhead than querying about a
> single host) and running all the results to nagios as passive checks. 
> The problem is that nagios uses a named pipe for the command file, and
> the buffer on linux is only 4k.  So I can't write all those checks at
> once as it would overrun the 4k buffer.
> 
> I looked and there's an option for nagios to check the file as often as
> possible, but I read the code and found out that's a lie.  I would think
> that using select(2) (as opposed to sleep(3)) would really allow nagios
> to check as often as possible.
> 
> Does anyone have any ideas of how to work around this?  Or has anyone
> already tried replacing that sleep() call with a select call()?
> 
> Thanks,
> 
> 
> Sean
> 
> 
> 
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