What are the best free tools for monitoring a set of servers running (mostly) Java apps? It would need to monitor several app servers (some JBoss, some Jetty, etc). All are started and stopped from the services system under Ubuntu or Debian via YAJSW (a service wrapper for Java applications).
What experiences have you had with the tools out there?
Right now, we are looking heavily at these three:
What are the real world experiences, and strengths/weaknesses of these? Are there any that we should specifically avoid?