WebSocket and multiple Dyno's on Heroku Node.js app Using Redis - node.js

Question

I'm building an App deployed to Heroku which uses WebSocket and Redis.
The WebSocket connection is working properly when I use only 1 dyno, but when I scale to 2, then I send event my application do it twice.
const ws = require('ws')
const jwt = require('jsonwebtoken')
const redis = require('redis')
const User = require('../models/user')
function verifyClient (info, callback) {
let token = info.req.headers['sec-websocket-protocol']
if (!token) { callback(false, 401, 'Unauthorized') } else {
jwt.verify(token, Config.APP_SECRET, (err, decoded) => {
if (err) { callback(false, 401, 'Unauthorized') } else {
if (info.req.headers.gameId) { info.req.gameId = info.req.headers.gameId }
info.req.userId = decoded.aud
callback(true)
}
})
}
};
let websocketServer, pub, sub
let clients = {}
let namespaces = {}
exports.initialize = function (httpServer) {
websocketServer = new ws.Server({
server: httpServer,
verifyClient: verifyClient
})
pub = redis.createClient(Config.REDIS_URL, { no_ready_check: true, detect_buffers: true })
pub.auth(Config.REDIS_PASSWORD, function (err) {
if (err) throw err
})
sub = redis.createClient(Config.REDIS_URL, { no_ready_check: true, detect_buffers: true })
sub.auth(Config.REDIS_PASSWORD, function (err) {
if (err) throw err
})
function handleConnection (socket) {
// socket.send(socket.upgradeReq.userId);
socket.userId = socket.upgradeReq.userId // get the user id parsed from the decoded JWT in the middleware
socket.isAlive = true
socket.scope = socket.upgradeReq.url.split('/')[1] // url = "/scope/whatever" => ["", "scope", "whatever"]
console.log('New connection: ' + socket.userId + ', scope: ' + socket.scope)
socket.on('message', (data, flags) => { handleIncomingMessage(socket, data, flags) })
socket.once('close', (code, reason) => { handleClosedConnection(socket, code, reason) })
socket.on('pong', heartbeat)
if (socket.scope === 'gameplay') {
try {
User.findByIdAndUpdate(socket.userId, { $set: { isOnLine: 2, lastSeen: Date.now() } }).select('id').lean()
let key = [socket.userId, socket.scope].join(':')
clients[key] = socket
sub.psubscribe(['dispatch', '*', socket.userId, socket.scope].join(':'))
} catch (e) { console.log(e) }
} else {
console.log('Scope : ' + socket.scope)
}
console.log('Connected Users : ' + Object.keys(clients))
}
function handleIncomingMessage (socket, message, flags) {
let scope = socket.scope
let userId = socket.userId
let channel = ['dispatch', 'in', userId, scope].join(':')
pub.publish(channel, message)
}
function handleClosedConnection (socket, code, reason) {
console.log('Connection with ' + socket.userId + ' closed. Code: ' + code)
if (socket.scope === 'gameplay') {
try {
User.findByIdAndUpdate(socket.userId, { $set: { isOnLine: 1 } }).select('id').lean()
let key = [socket.userId, socket.scope].join(':')
delete clients[key]
} catch (e) {
console.log(e)
}
} else {
console.log('Scope : ' + socket.scope)
}
}
function heartbeat (socket) {
socket.isAlive = true
}
sub.on('pmessage', (pattern, channel, message) => {
let channelComponents = channel.split(':')
let dir = channelComponents[1]
let userId = channelComponents[2]
let scope = channelComponents[3]
if (dir === 'in') {
try {
let handlers = namespaces[scope] || []
if (handlers.length) {
handlers.forEach(h => {
h(userId, message)
})
}
} catch (e) {
console.log(e)
}
} else if (dir === 'out') {
try {
let key = [userId, scope].join(':')
if (clients[key]) { clients[key].send(message) }
} catch (e) {
console.log(e)
}
}
// otherwise ignore
})
websocketServer.on('connection', handleConnection)
}
exports.on = function (scope, callback) {
if (!namespaces[scope]) { namespaces[scope] = [callback] } else { namespaces[scope].push(callback) }
}
exports.send = function (userId, scope, data) {
let channel = ['dispatch', 'out', userId, scope].join(':')
if (typeof (data) === 'object') { data = JSON.stringify(data) } else if (typeof (data) !== 'string') { throw new Error('DispatcherError: Cannot send this type of message ' + typeof (data)) }
pub.publish(channel, data)
}
exports.clients = clients
This is working on localhost.
Please let me know if I need to provide more info or code.Any help on this would be greatly appreciated, thanks in advance!

Answer 1

You have alot of extraneous info in the code you posted, so it's difficult to understand exactly what you mean.
However, if I understand correctly, you currently have multiple worker dyno instances subscribing to the same channels in some kind of pub/sub network. If you don't want all dynos to subscribe to the same channels, you need to put some logic in to make sure that your channels get distributed across dynos.
One simple way to do that might be to use something like the logic described in this answer.
In your case you might be able to use socket.userId as the key to distribute your channels across dynos.