Node.js cluster uses IPC (Inter-Process Communication) channels to allow message passing between the master and worker processes using worker.send() from the master and process.send() from the worker, with corresponding 'message' event listeners on both sides.
Each worker automatically has an IPC channel established with the master at the time of forking. Messages are serialized as JSON internally, so you can pass any JSON-serializable data. This is the primary way to coordinate shared state or tasks across workers since they cannot share memory directly.
Sending configuration updates to all workers dynamically
Aggregating metrics or counters from workers into the master
Notifying the master when a worker is ready or busy
Broadcasting messages to all workers from the master
Coordinating graceful shutdown sequences