Everything is a Freaking DNS problem

During my Puppetcamp Gent talk last week, I explained how to get alerts based on trends from graphite. A number of people asked ,e how to do that.

First lets quickly explain why you might want to do that .
Sometimes you don't care about the current value of a metric..as an example take a Queing system .. there is no problem if there are messages added to the queue, not even if there are a lot of messages on the queue, there might however be a problem if over a certain period the number of messages on a queue stays to high.

In this example I`m monitoring the queue length of a hornetq setup which is exposed by JMX.
On the server runnnig HornetQ I have an exported resource that tells the JMXTrans server to send the MessageCount to graphite
(you could also do this using collectd plugins)

@@jmxtrans::graphite {"MessageCountMonitor-${::fqdn}":
    jmxhost => hiera('hornetqserver'),
            jmxport => "5446",
            objtype => 'org.hornetq:type=Queue,*',
            attributes =>  '"MessageCount","MessagesAdded","ConsrCount"',
            resultalias => "hornetq",
            typenames => "name",
            graphitehost => hiera('graphite'),
            graphiteport => "2003",
}

This gives me a computable url on which I can get the graphite view

The next step then is to configure a nagios check that verifies this data. For that I need to use the check_graphite plugin from Datacratic ..

Which can work with an nrpe config like

### File managed with puppet ###
### Served by:        '<%= scope.lookupvar('::servername') %>'
### Module:           '<%= scope.to_hash['module_name'] %>'
### Template source:  '<%= template_source %>'
 
command[check_hornetq]=/usr/lib64/nagios/plugins/check_graphite -u "http://<%= graphitehost%>/render?target=servers.<%= scope.lookupvar('::fqdn').gsub(/\./,'_')%>_5446.hornetq.docstore_private_trigger_notification.MessageCount&from=-30minutes&rawData=true" -w 2000 -c 20000

I define this check on the host where HornetQ is running as it then will map to that host on Icinga/Nagios rather than throw a host error on an unrelated host.