The simple way would be use use nrpe and check_proc. I have never tested, but a command like 'ps -ef | grep java | grep NameNode' would be a fairly decent check. That is not very robust but it should let you know if the process is alive.
You could also monitor the web interfaces associated with the different servers remotely. check_tcp!hadoop1:56070 Both the methods I suggested are quick hacks. I am going to investigate the JMX options as well and work them into cacti
