Best free network monitoring tool for a handful of servers running (mostly) Java apps?

Question

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:

• Hyperic
• OpenNMS
• Pandora FMS

What are the real world experiences, and strengths/weaknesses of these? Are there any that we should specifically avoid?

Answer 1

I like nagios personally. Quite configurable with all kinds of things you can monitor.

Answer 2

I have found ZenOss Core is pretty simple to use to monitor Java / JBoss apps - it also doesn't require any plugins / wars added to your Java / JBoss configuration to monitor. ZenOss' biggest let down for me is that its quite heavy when monitoring only a small set of services - that said it does seem to scale extremely well. On similar hardware I've monitored 20 services up to 1000 services without much noticeable load change. If you have a machine you can dedicate to monitoring with 512+Mb RAM - very nice choice.