check scheduling when checks are inhibited.

[Paul M. Dubuc]

We're using Nagios 3.2.3 for simulation of monitoring load in a load test 
environment as well as for monitoring production services.  I've notices some 
interesting behavior in the way Nagios schedules checks when checks are 
inhibited either though the CGI Process Commands or by setting a check_period 
timeperiod that inhibits checks during regularly scheduled down times.

Normally Nagios seems to spread out host and service checks evenly over time 
but when checks are stopped with the Process Command, Nagios seems to 
reschedule checks so that they are "bunched up" much closer together.  This 
creates alternating periods of densely scheduled and more sparsely scheduled 
checks that seem to persist when checks are turned on again.  It has a 
noticeable effect in our load testing.  The only way--or the quickest way--to 
get Nagios to smooth out the schedule again is to stop the process completely 
until all the scheduled check times have passed.

In testing Nagios monitoring of our production services, if I use the 
check_period to inhibit checks during our down times, I notice that as the 
downtime approaches, ALL checks are rescheduled for the exact time that the 
downtime ends (according to the check_period).  This creates a big spike in 
monitoring activity after the downtime.  One way to avoid this, I think, is to 
let checks run during the down times but inhibit notifications instead by 
using the timeperiod to define a notification_period.  But I wonder if this 
"bunching" up of the schedule when using check_periods is ever a desirable 
behavior.

These aren't critical issues for us since we can work around them 
procedurally.  But I wonder if there his a way to prevent the scheduled checks 
from getting bunched together like this if/when you need to inhibit checks for 
a time while keeping Nagios running. Maybe the auto_rescheduling options in 
the nagios.cfg are meant to address this, but they have a potentially negative 
effect on performance according to the comments around them in the file.

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