Hadoop’s NameNode, SecondaryNameNode, DataNode, JobTracker, and TaskTracker daemons all expose runtime metrics. These are handy for monitoring and ad-hoc exploration of the system and provide a goldmine of historical data when debugging.
In this post, I’ll first talk about saving metrics to a file. Then we’ll walk through some of the metrics data. Finally, I’ll show you how to configure sending metrics to other systems and explore them with jconsole.