Nagios dependency question

[John Maddalozzo]

On Thu, 26 Dec 2002, Scott Whitney wrote:

> Background:
> a) Nagios runs "here"
> b) There is a router "here"
> c) It goes across the Internet to my coloc site (call it "there")
> d) There is a router "there"
> e) For the purposes of this example, there is 1 "machine" there
> f) "machine" runs httpd
> g) this httpd is shared for all web apps on the box, of which there are 55
> h) I have a script which checks the status of this web app.
> 
> Here's my problem.  When the router, here, is down, I get 59 messages.  That
> is, router "here", router "there", machine ping, machine httpd + 55 sites.

No, actually you don't get the "site down" messages, but you do (or
did) get the "machine down" messages. At least that is what was happening
the other day. 

I already put in an additional dependency ( I think it is on the
coloc-router) for the machine notifications. I think this is covered now,
but I haven't tested it. Should be able to test it by unplugging the T1.

Note there are two types of dependencies. host and service. I added the
service dependency. The host dependency was already there. 

I don't understand your math below.

> 
> I can solve this using dependencies, but here's my question.
> 
> For the dependencies to work properly, each of the sites must be dependent
> on:
>     a) httpd
>     b) ping machine
>     c) ping router "there"
>     d) ping router "here"
> 
> Let's assume I check this every minute.  My math says that this is roughly
> 280 hits on httpd per minute (55 * 5 + 5), 280 pings to the machine per

Huh? What's the *5? and +5?

> minute, 280 pings to the router there per minute and 280 pings to the router
> here per minute.
> 
> This gets a little worse when you realize I actually have over 200 sites,
> not 55.  Also on 7 boxes, not one, so we're looking at more like 1005 per
> minute, spread unevenly across several boxes.
> 
> The question, then, is whether anyone has run into this and/or does Nagios
> take this into consideration via any caching mechanism?  The documentation
> says
> 
> "Before Nagios executes a service check or sends notifications out for a
> service, it will check to see if the service has any dependencies. If it
> doesn't have any dependencies, the check is executed or the notification is
> sent out as it normally would be. If the service does have one or more
> dependencies, Nagios will check each dependency entry as follows:
> Nagios gets the current status* of the service that is being depended upon.
> "
> 
> * by default this is the current HARD state

I presume either out of the state file, or it's image in shared mem. 

> 
> So...from where is it getting this information?  Further perusal through the
> theory section helps me not at all...
> 
> Anyone have ideas on this?
> 
> Thanks,
> 
> Scott Whitney
> swhitney at Journyx.com
> 

-- 
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