Nimbus

The Nimbus node is the master in a Storm cluster. It is responsible for distributing the application code across various worker nodes, assigning tasks to different machines, monitoring tasks for any failures, and restarting them as and when required.

Nimbus is stateless and stores all of its data in ZooKeeper. There is a single Nimbus node in a Storm cluster. If the active node goes down, then the passive node will become an Active node. It is designed to be fail-fast, so when the active Nimbus dies, the passive node will become an active node, or the down node can be restarted without having any effect on the tasks already running on the worker nodes. This is unlike Hadoop, where if the JobTracker dies, all the running jobs are left in an inconsistent state and need to be executed again. The Storm workers can work smoothly even if all the Nimbus nodes go down but the user can't submit any new jobs into the cluster or the cluster will not be able to reassign the failed workers to another node.