CODEWITHSUNDEEP
node.jsmultithreadingsocketswebsocketchild-process
JacobFischer
JacobFischer

Reputation: 723

How to pass an active WebSocket to a clustered thread in Node.js?

In Node.js they expose a handy way to pass net.Sockets to child processes (cluster.Worker) via:

var socket; // some instance of net.Socket
var worker = process.fork();
worker.on("online", function() {
    worker.send("socket", socket);
});

Which is super cool and works handily. But how would I do this with a WebSocket connection? I'm open to try any module.

Currently I've tried using various modules like ws. Most of them store the initial net.Socket HTTP Request and then upgrade it, but none seem simple enough to pass to the child process as a net.Socket because they need tons of handshake info needed by the WebSocket spec, so far as I can tell.

I know there are hackish solutions, like opening a WebSocket server on the child process on a unique port, then telling the WebScoket connection to reconnect on that port, but then I need an open port for every child thread. Or, piping all data to the WebSocket connection through process.send so the main thread does all the io, but that defeats some of the performance benefits by running stuff on multiple threads.

So does anyone have any ideas?

Upvotes: 3

Views: 4072

Answers (1)

JacobFischer
JacobFischer

Reputation: 723

Welp I figured it out. ws may have been too much for my intended purposes. Instead I found a pretty obscure WebSocket library, lark-websocket which exposes a function that given a net.Socket can wrap it up in in their Client class and work with it as a WebSocket. The only issue was both the parent and child threads would then try to ping the connection on the other end so I had to fork it and add a way for the parent thread to pause pinging.

Here's some example code for anyone interested:

var cluster = require("cluster");
var ws = require('lark-websocket');

if(cluster.isMaster) { // make a child process and pipe all ws connections to it
    var worker = cluster.fork();

    worker.once("online", function() {
        console.log("worker online with pid", worker.process.pid);
    })

    ws.createServer(function(client, request){
        worker.send("socket", client._socket); // send all websocket clients to the worker thread
    }).listen(27015);
}
else { // we are a worker, so we handle the ws connections
    process.on("message", function(message, handler) {
        if(message === "socket") { // Note: Node js can only send sockets via handler if message === "socket", because passing sockets between threads is sketchy as fuck
            var client = ws.createClient(handler);

            client.on('message',function(msg){
                console.log("worker " + process.pid + " got:", msg);
                client.send("I got your: " + msg);
            });
        }
    });
}

Upvotes: 3

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