Storm architecture and its components

Let's discuss Storm architecture and how it works. The following figure depicts the Storm cluster:

• The Nimbus node acts as the master node in a Storm cluster. It is responsible for analyzing topology and distributing tasks to different supervisors as per their availability. Also, it monitors failure; if one of the supervisors dies, it redistributes the tasks among available supervisors. The Nimbus node uses Zookeeper to keep track of tasks to maintain it's state. If the Nimbus node fails, it can be restarted so that it reads the state of Zookeeper and starts from same point where it failed earlier.
• Supervisors act as slave nodes in the Storm cluster. One or more workers, that is, JVM processes, can run in each supervisor node. A supervisor coordinates with workers to complete the tasks assigned by Nimbus node. In the case of worker process failure, the supervisor finds available workers to complete the tasks.
• A worker process is a JVM running in a supervisor node. It has executors. There can be one or more executors in a worker process. A worker coordinates with an executor to finish up the task.
• An executor is a single thread process spawned by a worker. Each executor is responsible for running one or more tasks.
• A task is a single unit of work. It performs actual processing on data. It can be either a spout or a bolt.
• Apart from previous processes, there are two important parts of a Storm cluster; they are logging and Storm UI. The logviewer service is used to debug logs for workers and supervisors on Storm UI.