如何使用 Node.js 集群将消息（对象）从 worker 发送到 Master（主）

Question

It seems that the message I send from the worker is not the one I received with the Master. I should receive {test: true} and I receive this long object with all these properties.

Maybe it can help to know that when I change the place of the event listener and place it into the worker creation loop (for (let i = 0; i < 2; i++) {let worker = cluster.fork()}), I receive the correct one ({test: true}).

What am I missing?

This is the code :

if (cluster.isMaster) {
            console.log(`Master ${process.pid} is running`)

            cluster.on('message', (msg) => {
                    if (msg.test) {
                        console.log('✅')
                    } else {
                        console.log('Message received without the content "test : true"')
                    }
                    console.log('--------- msg : , 'msg)

                })

            for (let i = 0; i < 2; i++) {
                let worker = cluster.fork()
            }

        } else {
            setTimeout(() => {
                process.send({test: true})
            }, 1000)

        }

This is the terminal output :

Master 84458 is running
Message received without the content "test : true"
Message received without the content "test : true"


--------- msg : {
  _events: [Object: null prototype] { message: [Function (anonymous)] },
  _eventsCount: 1,
  _maxListeners: undefined,
  exitedAfterDisconnect: undefined,
  state: 'online',
  id: 2,
  process: <ref *1> ChildProcess {
    _events: [Object: null prototype] {
      internalMessage: [Array],
      error: [Function (anonymous)],
      message: [Function (anonymous)],
      exit: [Function],
      disconnect: [Function]
    },
    _eventsCount: 5,
    _maxListeners: undefined,
    _closesNeeded: 2,
    _closesGot: 0,
    connected: true,
    signalCode: null,
    exitCode: null,
    killed: false,
    spawnfile: '/usr/local/bin/node',
    _handle: Process {
      onexit: [Function (anonymous)],
      pid: 83453,
      [Symbol(owner_symbol)]: [Circular *1]
    },
    spawnargs: [
      '/usr/local/bin/node',
      '/home/stef/Dev/apps/Trading-Center/index.js'
    ],
    pid: 83453,
    stdin: null,
    stdout: null,
    stderr: null,
    stdio: [ null, null, null, null ],
    channel: Control {
      _events: [Object: null prototype] {},
      _eventsCount: 0,
      _maxListeners: undefined,
      [Symbol(kCapture)]: false
    },
    _handleQueue: null,
    _pendingMessage: null,
    send: [Function (anonymous)],
    _send: [Function (anonymous)],
    disconnect: [Function (anonymous)],
    _disconnect: [Function (anonymous)],
    [Symbol(kCapture)]: false,
    [Symbol(kChannelHandle)]: Pipe {
      pendingHandle: null,
      sockets: [Object],
      buffering: false,
      [Symbol(kJSONBuffer)]: '',
      [Symbol(kStringDecoder)]: [StringDecoder]
    }
  },
  [Symbol(kCapture)]: false
}

Answer 1

Your problem is at the message listener callback, the first parameter is the worker object, the second is the message object. The log you posted, is the worker itself.

Change from:

cluster.on('message', (msg)

To:

cluster.on('message', (worker, msg)

PS: I've put up a sample demo here , open the terminal and type node app.js to run the app.