How do I create a direct communication channel between two worker threads in Node.js

Question

Is there a way to create a direct communication channel using new MessageChannel between two worker threads? For Eg: There is a main thread P that I have created using the worker_thread API, which creates two worker threads W1 and W2

P -> W1
  -> W2

I want to enable communication between W1 and W2 directly instead of going via P using parentPort.

Answer 1

Use new MessageChannel() to generate a two-way communications channel.

index.js

const { Worker } = require('worker_threads');

const path = require('path'); 

const w1 = new Worker(path.join(__dirname,'./worker1.js'));
const w2 = new Worker(path.join(__dirname,'./worker2.js'));

w1.once('message', value => {
    w2.postMessage({
        port: value.port
    }, [value.port]);
});

w2.once('message', value => {
    w1.postMessage({
        port: value.port
    }, [value.port]);
});

worker1.js

const { MessageChannel, parentPort,  } = require('worker_threads');

let woker2Port;
console.log('worker1 started');

const { port1, port2 } = new MessageChannel();
port1.on('message', (value) => {
    console.log(value);
});

parentPort.postMessage({
    port: port2,
}, [port2]);

parentPort.on('message', value => {
    if (value.port) {
        woker2Port = value.port;
        woker2Port.postMessage({msg:'i am worker1!'});// send msg to worker2
        return;
    }
});

worker2.js

const { MessageChannel, parentPort,  } = require('worker_threads');

let woker1Port;
console.log('worker2 started');

const { port1, port2 } = new MessageChannel();
port1.on('message', (value) => {
    console.log(value);
});

parentPort.postMessage({
    port: port2,
}, [port2]);

parentPort.on('message', value => {
    if (value.port) {
        woker1Port = value.port;
        woker1Port.postMessage({msg:'i am worker2!'});// send msg to worker1
    }
});

Notice: if you debug this code in VSCode, you won't see the log print in worker1.js and worker2.js. Run node index directly or debug it in ndb works fine!