How do I deploy socket.io to Google App Engine?

Question

I created my first node.js app using socket.io. Specifically I implemented the chat example published by socket.io. It works perfectly, locally. And then I tried deploying it to Google App Engine (making some code tweaks for node to work).

Everything shows up indicating that the node part is working well. However the chat doesn't work indicating that socket.io part isn't working. You can see the deployed app (and page source) here.

Do I have to do anything additional? Something in the yaml or json files?

yaml content:

runtime: nodejs
vm: true

skip_files:
  - ^(.*/)?.*/node_modules/.*$

json content:

{
  "name": "Chaty",
  "description": "chatrooms app",
  "version": "0.0.1",
  "private": true,
  "license": "Apache Version 2.0",
  "author": "McChatface",
  "engines": {
    "node": "~4.2"
  },
  "scripts": {
    "start": "node app.js",
    "monitor": "nodemon app.js",
    "deploy": "gcloud preview app deploy"
  },
  "dependencies": {
    "express": "^4.13.4",
    "socket.io": "^1.4.6"
  }
}

Answer 1

Google has an example app using WebSockets here, you need to do the following to get it working correctly:

• Open up a firewall port for the server so clients can reach your server
• Fetch your internal IP in Google App Engine, so clients know what IP to connect to
• Echo out your IP from your server via something like a rest API or a HTML page

That should be it (don't take my word for it though, this is what I've been able to find out after doing some research on the docs), hope it helps!

Fetching your external IP from within Google App Engine

var METADATA_NETWORK_INTERFACE_URL = 'http://metadata/computeMetadata/v1/instance/network-interfaces/0/access-configs/0/external-ip';

function getExternalIp (cb) {
    var options = {
        url: METADATA_NETWORK_INTERFACE_URL,
        headers: {
            'Metadata-Flavor': 'Google'
        }
    };

    request(options, function (err, resp, body) {
        if (err || resp.statusCode !== 200) {
            console.log('Error while talking to metadata server, assuming localhost');
            return cb('localhost');
        }

        return cb(body);
    });
}

Opening the firewall port

gcloud compute firewall-rules create default-allow-websockets \
    --allow tcp:65080 \
    --target-tags websocket \
    --description "Allow websocket traffic on port 65080"

Answer 2

In short this cannot be done on production and it appears to be work in process. The right architecture is to have a chat server on google compute engine as outlined here.

But as a proof of concept to use socket.io on google app engine is very similar to that shown in google appengine samples for websockets.

In case of socket.io do the following steps on server side. Code snippet below.

1. Create second express middleware and server.
2. Attach/use socket.io with new server.
3. Listen to port (65080).
4. Open firewall for port (65080) on google compute engine.
5. Link to working repository.

---

socket.io changes on server side

    var app_chat = require('express')();
    var server1 = require('http').Server(app_chat);
    var io = require('socket.io')(server1);
    server1.listen(65080);

    io.on('connection', function (socket) {
      console.log('user connected');
      socket.on('chat_message', function (data) {
        console.log('client sent:',data);
        socket.emit('chat_message', 'Server is echoing your message: ' + data);
      });
    });

---

open firewall by command

gcloud compute firewall-rules create default-allow-websockets \
    --allow tcp:65080 \
    --target-tags websocket \
    --description "Allow websocket traffic on port 65080"

---

I hope Google comes up with a production-ready solution soon enough on as this will become a key armour in any PaaS-arsenal.