How to handle multiple, dynamically created listeners to a single ChildProcess in NodeJS?

[Konrad Moskal]

Hello!

So, I think I made a design mistake.

I have a child process worker, that receives some data and sends back the results to dynamically attached listener.

Simplified code:

    //app.js
    var worker = childProcess.fork('./app_modules/workers/worker1.js');
    worker.setMaxListeners(0);
    require('./app_modules/sockets-user/foobar.js')(io, worker);


    //foobar.js
    io.sockets.on('connection', function (socket) {
      socket.on('trigger', function (data) {
        worker.send(data);
        worker.once('message', function(responseData) {
       
          //here I get a response from worker
          socket.emit('response', responseData);
       
        });
      });
    });

It was working great until I discovered that If socket.on('trigger' is triggered at the very exact moment by different users every listener would receive the same message.

I could change worker.once to worker.on and filter incoming messages but its not really a fix. I would have to destroy every listener after it was used to prevent them from adding up and I don't know if it is even possible.

I did pass the worker object like that, because I thought I could pass it anywhere it was needed, now I feel like I was wrong. How should I approach this problem?

[Konrad Moskal]

I have already found out that this should be a reasonable solution, right? :)

//foobar.js
worker.on('message', function(responseData) {
  // assuming worker returns `{id: ..., data: ...}`
  var socket = io.sockets.sockets[responseData.id];
  socket.emit('response', responseData.data);
});

io.sockets.on('connection', function (socket) {
  socket.on('trigger', function (data) {

    worker.send({ id: socket.id, data: data });
  });
});

[Sam Roberts]

none of your code shows the definition of `io`, so its not possible to comment.

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