What happens when a Storm worker or node fails?
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Storm restarts it automatically. If a worker process dies, its supervisor restarts it. If a whole node dies, its work is reassigned to other nodes. The Nimbus and Supervisor daemons are stateless and fail-fast, keeping their state in ZooKeeper or on disk, so they can be killed and restarted without affecting running topologies.
Storm is fault-tolerant: when workers die, Storm will automatically restart them. If a node dies, the worker will be restarted on another node.
The Storm daemons, Nimbus and the Supervisors, are designed to be stateless and fail-fast. So if they die, they will restart like nothing happened. This means you can kill -9 the Storm daemons without affecting the health of the cluster or your topologies.
Read more about Storm's fault-tolerance on the manual.