[docs] Add haproxy cluster example (#2818)

examples/cluster-haproxy/README.md

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+
+# Socket.IO Chat with haproxy & redis
+
+A simple chat demo for socket.io
+
+## How to use
+
+Install [Docker Compose](https://docs.docker.com/compose/install/), then:
+
+```
+$ docker-compose up -d
+```
+
+And then point your browser to `http://localhost:3000`.
+
+This will start four Socket.IO nodes, behind a haproxy instance which will loadbalance the requests (using a cookie for sticky sessions, see [cookie](https://cbonte.github.io/haproxy-dconv/1.7/configuration.html#4.2-cookie)).
+
+Each node connects to the redis backend, which will enable to broadcast to every client, no matter which node it is currently connected to.
+
+```
+# you can kill a given node, the client should reconnect to another node
+$ docker-compose stop server-george
+```
+
+## Features
+
+- Multiple users can join a chat room by each entering a unique username
+on website load.
+- Users can type chat messages to the chat room.
+- A notification is sent to all users when a user joins or leaves
+the chatroom.

examples/cluster-haproxy/docker-compose.yml

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+
+haproxy:
+  build: ./haproxy
+  links:
+    - server-john
+    - server-paul
+    - server-george
+    - server-ringo
+  ports:
+   - "3000:80"
+
+server-john:
+  build: ./server
+  links:
+    - redis
+  expose:
+    - "3000"
+  environment:
+    - NAME=John
+
+server-paul:
+  build: ./server
+  links:
+    - redis
+  expose:
+    - "3000"
+  environment:
+    - NAME=Paul
+
+server-george:
+  build: ./server
+  links:
+    - redis
+  expose:
+    - "3000"
+  environment:
+    - NAME=George
+
+server-ringo:
+  build: ./server
+  links:
+    - redis
+  expose:
+    - "3000"
+  environment:
+    - NAME=Ringo
+
+redis:
+  image: redis:alpine
+  expose:
+    - "6379"

examples/cluster-haproxy/haproxy/Dockerfile

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+FROM haproxy:1.7-alpine
+COPY haproxy.cfg /usr/local/etc/haproxy/haproxy.cfg

examples/cluster-haproxy/haproxy/haproxy.cfg

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+# Reference: http://blog.haproxy.com/2012/11/07/websockets-load-balancing-with-haproxy/
+
+global
+  daemon
+  maxconn 4096
+  nbproc 2
+
+defaults
+  mode http
+  balance roundrobin
+  option http-server-close
+  timeout connect     5s
+  timeout client      30s
+  timeout client-fin  30s
+  timeout server      30s
+  timeout tunnel      1h
+  default-server inter 1s rise 2 fall 1 on-marked-down shutdown-sessions
+  option forwardfor
+
+listen chat
+  bind *:80
+  default_backend nodes
+
+backend nodes
+  option httpchk HEAD /health
+  http-check expect status 200
+  cookie serverid insert
+  server john    server-john:3000    cookie john   check
+  server paul    server-paul:3000    cookie paul   check
+  server george  server-george:3000  cookie george check
+  server ringo   server-ringo:3000   cookie ringo  check

examples/cluster-haproxy/server/Dockerfile

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+FROM mhart/alpine-node:6
+
+# Create app directory
+RUN mkdir -p /usr/src/app
+WORKDIR /usr/src/app
+
+# Install app dependencies
+COPY package.json /usr/src/app/
+RUN npm install
+
+# Bundle app source
+COPY . /usr/src/app
+
+EXPOSE 3000
+CMD [ "npm", "start" ]

examples/cluster-haproxy/server/index.js

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+// Setup basic express server
+var express = require('express');
+var app = express();
+var server = require('http').createServer(app);
+var io = require('socket.io')(server);
+var redis = require('socket.io-redis');
+var port = process.env.PORT || 3000;
+var serverName = process.env.NAME || 'Unknown';
+
+io.adapter(redis({ host: 'redis', port: 6379 }));
+
+server.listen(port, function () {
+  console.log('Server listening at port %d', port);
+  console.log('Hello, I\'m %s, how can I help?', serverName);
+});
+
+// Routing
+app.use(express.static(__dirname + '/public'));
+
+// Health check
+app.head('/health', function (req, res) {
+  res.sendStatus(200);
+});
+
+// Chatroom
+
+var numUsers = 0;
+
+io.on('connection', function (socket) {
+  socket.emit('my-name-is', serverName);
+
+  var addedUser = false;
+
+  // when the client emits 'new message', this listens and executes
+  socket.on('new message', function (data) {
+    // we tell the client to execute 'new message'
+    socket.broadcast.emit('new message', {
+      username: socket.username,
+      message: data
+    });
+  });
+
+  // when the client emits 'add user', this listens and executes
+  socket.on('add user', function (username) {
+    if (addedUser) return;
+
+    // we store the username in the socket session for this client
+    socket.username = username;
+    ++numUsers;
+    addedUser = true;
+    socket.emit('login', {
+      numUsers: numUsers
+    });
+    // echo globally (all clients) that a person has connected
+    socket.broadcast.emit('user joined', {
+      username: socket.username,
+      numUsers: numUsers
+    });
+  });
+
+  // when the client emits 'typing', we broadcast it to others
+  socket.on('typing', function () {
+    socket.broadcast.emit('typing', {
+      username: socket.username
+    });
+  });
+
+  // when the client emits 'stop typing', we broadcast it to others
+  socket.on('stop typing', function () {
+    socket.broadcast.emit('stop typing', {
+      username: socket.username
+    });
+  });
+
+  // when the user disconnects.. perform this
+  socket.on('disconnect', function () {
+    if (addedUser) {
+      --numUsers;
+
+      // echo globally that this client has left
+      socket.broadcast.emit('user left', {
+        username: socket.username,
+        numUsers: numUsers
+      });
+    }
+  });
+});

examples/cluster-haproxy/server/package.json

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+{
+  "name": "socket.io-chat",
+  "version": "0.0.0",
+  "description": "A simple chat client using socket.io",
+  "main": "index.js",
+  "author": "Grant Timmerman",
+  "private": true,
+  "license": "BSD",
+  "dependencies": {
+    "express": "4.13.4",
+    "socket.io": "^1.7.2",
+    "socket.io-redis": "^3.0.0"
+  },
+  "scripts": {
+    "start": "node index.js"
+  }
+}

examples/cluster-haproxy/server/public/index.html

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+<!doctype html>
+<html lang="en">
+<head>
+  <meta charset="UTF-8">
+  <title>Socket.IO Chat Example</title>
+  <link rel="stylesheet" href="style.css">
+</head>
+<body>
+  <ul class="pages">
+    <li class="chat page">
+      <div class="chatArea">
+        <ul class="messages"></ul>
+      </div>
+      <input class="inputMessage" placeholder="Type here..."/>
+    </li>
+    <li class="login page">
+      <div class="form">
+        <h3 class="title">What's your nickname?</h3>
+        <input class="usernameInput" type="text" maxlength="14" />
+      </div>
+    </li>
+  </ul>
+
+  <script src="https://code.jquery.com/jquery-1.10.2.min.js"></script>
+  <script src="/socket.io/socket.io.js"></script>
+  <script src="/main.js"></script>
+</body>
+</html>