If you hadn’t already guessed I am a big fan of the Xen hypervisor. Lately I have been using the Citrix XenServer release because it makes it quite palatable for my co-workers. One annoyance that I do have about XenServer is the requirement that you license it (with a free license) every year. If you fail to license it the GUI stops working. Now I hate relying on GUIs but the fact of the matter is others in my team expect to have a working GUI when they need to do something. And I dont know about you but I don’t really log onto the management console very often. Really I only log on to it if I need to provision a new server so its entirely plausible that a license would expire and I wouldn’t know about it until I really needed to do something.
I ended up writing a little Nagios plugin that checks the license expiration date using XenAPI. I don’t know that it’s 100% compliant with the plugin specification but it does work for me. I actually don’t prefer to use the warn and critical states with the Nagios (I use the performance data with Zenoss and apply thresholds there. I find that to be a bit more flexible.) but I did implement them. The plugin can be executed on the XenServer (you may want to reference how to install nrpe on XenServer) or on from your monitoring host as long as the host performing the check has the python XenAPI installed.
I hope someone can find it useful.