JMX is widely used in Java world to stream metrics and KPIs.
In Hadoop, the most used JMX is on the NameNode :
This provides an overview of all the things accessible through JMX :
You can have a list of all metrics provided by JMX :
And you can finally (which is very useful if you’re looking at something very specific) get a specific metric when specifying the bean name and the attribute :
For example, if we want to get the CapacityUsed found here :
Then we’ll call JMX with MXBeanName = Hadoop:service=NameNode,name=FSNamesystemState and AttributeName set to CapacityUsed