What is it?
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.
The site is jrds.fr
How it works?
JRDS is a java web application, that can run in any servlet server like tomcat or resin. It can also run in a standalone mode, using jetty.
It uses threads to parallelize work. 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. Additional collectors can be used using external jars.