[Nagiosplug-devel] Check_ping question

[Sean Dilda]

On Wed, 2004-11-10 at 19:41, Andreas Ericsson wrote:

> > I guess I also am confused on this one, as /bin/ping on most OS's will
> > send packet 2 at 1000ms, and packet 3 at 2000ms, with a 5000 ms timeout,
> > that's 7.0000000001 seconds total. Why are we going all the way up to
> > 18, or even 15 seconds then?
> > 
> 
> It's just the maximum. check_ping doesn't have a backoff factor (which 
> is what you describe), since it forks system ping to do its dirtywork.

How does check_ping not have that?  I ran some tests.  If you tell
check_ping to send 3 packets, it calls ping once and tells ping to send
3 packets.  Therefore, check_ping sends the packets out at one-second
intervals because ping sends them out at one-second intervals.  So, if
you have a 5 second critical timeout, and are sending 3 packets, the
maximum theoretical timeout is just over 7 seconds (as Robert pointed
out).  Waiting for 15+ seconds is just wasted time.

Having seen what happens to a nagios system that undergoes a massive
network outage (with few network switches defined), I think its very
important that the check-host-alive plugins not waste more time than
they can.  (This is due in large part to the fact that nagios serializes
them.)