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!

Answer 2

Perhaps you can try this:

const {Worker, isMainThread, parentPort, MessageChannel } = require('node:worker_threads');
    
    if(isMainThread)
    {
        let worker1 = new Worker(__filename,{argv:['worker1']})
        let worker2 = new Worker(__filename,{argv:['worker2']})
    
    const {port1, port2} = new MessageChannel

    worker1.postMessage({port:port1},[port1])
    worker2.postMessage({port:port2},[port2])

}
else
{
    //use process.argv to differentiate between worker1 and worker2
    let workerName = process.argv[2]

    parentPort.once('message',value=>{
        let myport = value.port

        myport.on('message',(data)=>{
            console.log(`${workerName} got:${data}`)
            //every time the data was increacsed by 1
            setTimeout(()=>{myport.postMessage(data+1)},1000)
        })

        if(workerName === 'worker1')
        {
            //let worker1 to send the intial message
            myport.postMessage(1)
        }
    })
}