What is the difference between the master process and a worker process in Node.js clustering?

The master process is responsible for managing the lifecycle of worker processes — spawning, monitoring, and restarting them. Worker processes contain the actual application logic and handle incoming client requests independently.

In a clustered Node.js application, the roles of the master and worker processes are clearly separated. The master process acts as an orchestrator — it never handles HTTP requests directly. Workers are the actual application servers that process requests and respond to clients.

Master Process Responsibilities

1
Spawn worker processes using cluster.fork()
2
Monitor worker health and listen for exit events
3
Restart dead workers automatically
4
Distribute incoming connections to available workers
5
Send configuration or messages to workers via IPC

Worker Process Responsibilities

1
Run the actual HTTP server or application logic
2
Handle incoming requests assigned by the master
3
Send and receive messages to/from the master via IPC
4
Operate independently with their own memory space

Master vs Worker Role Separation