[xwiki-users] Monitoring an Xwiki stack

Having made my XWiki site available to other users, I was concerned to find that the site became unusable at one point with client connections eventually timing out. I had no way to diagnose the problem, but eventually I managed to make a (slow) SSH connection to the server and restarted Tomcat, and things seemed to settle back to normal. The problem is I have no real sense of what happened and how to prevent it happening again. To that end, I'd appreciate any suggestions for monitoring the server and diagnosing poor performance. What do others typically use? I have an Apache2 server passing wiki page requests to Tomcat7 via an ajp connector, and a PostgreSQL database. My guess is that Tomcat is doing most of the work here so that's probably what I need to monitor the most.