Redirect HTTP upgrade to a websocket on another instance

I use Node cluster, on each worker there's a running websocket server. Master has a HTTP server running.

On the Master HTTP server I want a HTTP Upgrade call implementation, that will connect the caller to a specific web socket.

Why? I want to be able to connect user to a correct websocket, but I want to do it through a single entry point being localhost:8000. Connecting to localhost:8000 might connect you to localhost:8001 seamlessly.

My idea was to call Upgrade with a parameter like:

wscat -c ws://localhost:8000/?id=5

This call should go to the Master, and master would forward this upgrade call and make connection with localhost:8005.

I thought I could simply forward the upgrade params to the worker with worker.send(), but this doesn't really work, objects I receive in the worker miss a lot of things, it's probably some basics of JS I don't know about.

Here's my naive implementation:

var http = require('http');
var cluster = require('cluster')
var ws = require('ws');
var NumberOfInstances = 5;
if (cluster.isMaster) {
var forks = []
for (var i=0; i < NumberOfInstances; i++) {
forks.push(cluster.fork());
}
server = http.createServer((req, res) => {
res.writeHead(200);
}).listen(8000);
server.on('upgrade', (request, socket, head) => {
var params = new URL(`https://localhost:8000${request.url}`);
var id = parseInt(params.searchParams.get('clusterId')) - 1;
// How do I forward upgrade??
forks[id].send({r: request, s: socket, h: head});
})
} else {
portStr = `800${cluster.worker.id}`;
wss = new ws.WebSocketServer({
port: portStr
});
wss.on('connection', (ws, request) => {
console.log(`${cluster.worker.id} got connection.`);
})
process.on('message', masterMessage => {
// This absolutely doesn't work. 
wss.handleUpgrade(masterMessage.r, masterMessage.s, masterMessage.h, (ws) => {
wss.emit('connection', ws, masterMessage.r);
})
})
}

According to docs, you are required to send the socket handler as a second argument to the worker.send method.

So you should do this instead,

forks[id].send({ headers: request.headers, method: request.method, head: head }, socket); //socket is in second argument

and in your child message event handler, do this,

process.on('message', (request,socket) => {
wss.handleUpgrade(request, socket, request.head, (ws) => {
wss.emit('connection', ws, request);
})
})

Look at this example to see how to pass socket object as an argument.