Jrds is performance collector, much like cacti or munins. But it intends to be more easy to use and able to collect a high number of machines in a very short time. It's fully written in java and avoid call external process to increase performances. It uses RRD4J, a clone of rrdtool written in java.
A live demo can be found here (thanks to bougie).
It uses threads to parallize works. Each host is collected within the same thread and the number of simultaneous threads can be configured. It use only one thread for each host to avoid overload of a server.
It use mainly snmp to collect data, but can be easily extended. There is also some jdbc probes, a agent using RMI for the communication, and it can also parse XML data collected with HTTP. The currently available probes can be found here. Additionnal collectors can be used using external jars.
For bug submission, or more informations, you should go to the github projet page.
Jetty can be run in a application server like tomcat, or as a standalone daemon.
There is also the javadoc online.