Showing off all cluster events

cluster-events.js

const cluster = require("cluster");

if (cluster.isMaster) {

  function messageHandler(msg) {
    console.log(msg);
  }

  cluster.on("message", function (worker, message) {
    console.log(`master: (cluster.onMessage) '${message}'`);
  });

  // Never fires (not a bug)
  process.on("message", function (message) {
    console.log("master: process.onMessage", message);
  });

  for (var i = 0; i < 2; i++) {
    var worker = cluster.fork();
    worker.on("message", (function(i) {
      return function (message, otherarg) {
        // Event handler unique to this worker:
        console.log(`master: (worker[${i+1}].onMessage) '${message}'`);
      }
    })(i));
    // Docs: Send a message to a worker or master. ... In the master this
    // sends a message to the specified worker, identical to ChildProcess.send.
	console.log(`<-- master sending message to worker ${i+1}-->`);
    worker.send(`message from master to worker ${i+1}`);
  }

} else {
  // Docs: send a message to the master.
  console.log(`<-- worker${cluster.worker.id} sending message -->`);
  // These two are identical.
  //cluster.worker.send(`message from worker ${cluster.worker.id} (via cluster.worker.send)`);
  process.send(`message from worker ${cluster.worker.id} (via process.send)`);

  // These two are also identical:
  process.on("message", function (message) {
    console.log(`worker[${cluster.worker.id}]: (process.onMessage) '${message}'`);
  });
  cluster.worker.on("message", function (message) {
    console.log(`worker[${cluster.worker.id}]: (cluster.worker.onMessage) '${message}'`);
  });

  // Never fires
  cluster.on("message", function (worker, message) {
    console.log(`worker[${cluster.worker.id}]: (cluster.onMessage) '${message}'`);
  });
}

/*
Docs say:

Cluster: Worker: event: 'message'
	Similar to the cluster.on("message") event, but specific to this worker.
	In a worker you can also use process.on("message")

https://nodejs.org/dist/latest-v6.x/docs/api/cluster.html#cluster_event_message_1
Cluster: event: 'message'
	Emitted when any worker receives a message. // Receives!?
*/

output.txt

> node .\test-cluster.js
<-- master sending message to worker 1-->
<-- master sending message to worker 2-->
<-- worker1 sending message -->
master: (cluster.onMessage) 'message from worker 1 (via process.send)'
master: (worker[1].onMessage) 'message from worker 1 (via process.send)'
worker[1]: (cluster.worker.onMessage) 'message from master to worker 1'
worker[1]: (process.onMessage) 'message from master to worker 1'
<-- worker2 sending message -->
master: (cluster.onMessage) 'message from worker 2 (via process.send)'
master: (worker[2].onMessage) 'message from worker 2 (via process.send)'
worker[2]: (cluster.worker.onMessage) 'message from master to worker 2'
worker[2]: (process.onMessage) 'message from master to worker 2'