OpenNebula

It would be great to have some sort of metrics for monitoring the OpenNebula Core. Here are some metrics I would find useful:

- counters for each success and failed API calls
- authentication failures
- number of read/writes to the DB
- latency to the DB (time spent reading or writing)
- some stats on the internals (time spent waiting for a lock, number of failed lock request, etc.).

And have a method to easily export the metrics to ex. Ganglia (perhaps making metrics struct available to other processes through shared memory). The metrics should be very simple and lightweight, I'm thinking of plain counters that are initialized to 0 when OpenNebula starts.

The same metrics could be used for measuring the impacts of optimization / changes to the core or to the DB.