Passive service checks not being accepted by primary?

[Paul L. Allen]

Cliff Riggs writes: 

> log_passive_service_checks=1
> accept_passive_service_checks=1

If it is not possible to perform active checks, you need to disable
those for the relevant services.  Otherwise if the passive check gets
stale the active check will be performed and will probably fail with
a plugin timeout. 

It works that way so you can have distributed monitoring.  You can perform
the checks directly from the central server but you use distributed checks
to reduce the load on it.  In this case, if one of the remote servers goes
down the central server can take over.  Obviously in this case you need
enough spare capacity on the central server to cope if one (perhaps
more, if you have a lot of remote servers) of the remote servers goes
down. 

Having active checks enabled when they cannot actually be performed
will lead to misleading error messages.  You'll still know there is
a problem, but you'll be misled as to what the problem really is. 

> I did create a "check_dummy" command definition and apply it to my primary 
> host 'check_command' as Demetri suggested, but I did not yet enable 
> freshness checking as defined in the documentation. My understanding of 
> the documentation was that this was an add-on to make sure you are 
> regularly receiving updates from the remote server and not essential to 
> accepting passive service checks.

Freshness checking is not essential but it is desirable.  Without freshness
checking the remote server could die and you wouldn't know there is a
problem for a long time, depending exactly on how checks of various
services are scheduled (and especially if the remote server submits
passive checks for itself).  With freshness checking you know if a service
check result is overdue.  It's not perfect, because you have to allow
enough slop in the freshness check interval to cover worst-case shceduling,
which is not entirely deterministic. 

-- 
Paul Allen
Softflare Support 




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