docs(examples): update the nginx cluster example

Related: https://github.com/socketio/socket.io/discussions/3778

Reference: http://nginx.org/en/docs/http/ngx_http_upstream_module.html#hash

examples/cluster-nginx/README.md

@@ -22,6 +22,16 @@ Each node connects to the redis backend, which will enable to broadcast to every
 $ docker-compose stop server-george
 ```
 
+A `client` container is included in the `docker-compose.yml` file, in order to test the routing.
+
+You can create additional `client` containers with:
+
+```
+$ docker-compose up -d --scale=client=10 client
+# and then
+$ docker-compose logs client
+```
+
 ## Features
 
 - Multiple users can join a chat room by each entering a unique username

examples/cluster-nginx/client/Dockerfile

@@ -0,0 +1,15 @@
+FROM node:14-alpine
+
+# 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 --prod
+
+# Bundle app source
+COPY . /usr/src/app
+
+EXPOSE 3000
+CMD [ "npm", "start" ]

examples/cluster-nginx/client/index.js

@@ -0,0 +1,13 @@
+const socket = require('socket.io-client')('ws://nginx');
+
+socket.on('connect', () => {
+  console.log('connected');
+});
+
+socket.on('my-name-is', (serverName) => {
+  console.log(`connected to ${serverName}`);
+});
+
+socket.on('disconnect', (reason) => {
+  console.log(`disconnected due to ${reason}`);
+});

examples/cluster-nginx/client/package.json

@@ -0,0 +1,15 @@
+{
+  "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": "MIT",
+  "dependencies": {
+    "socket.io-client": "^2.4.0"
+  },
+  "scripts": {
+    "start": "node index.js"
+  }
+}

examples/cluster-nginx/docker-compose.yml

@@ -45,6 +45,11 @@ server-ringo:
   environment:
     - NAME=Ringo
 
+client:
+  build: ./client
+  links:
+    - nginx
+
 redis:
   image: redis:alpine
   expose:

examples/cluster-nginx/nginx/nginx.conf

@@ -24,8 +24,12 @@ http {
   }
 
   upstream nodes {
-    # enable sticky session
-    ip_hash;
+    # enable sticky session with either "hash" (uses the complete IP address)
+    hash $remote_addr consistent;
+    # or "ip_hash" (uses the first three octets of the client IPv4 address, or the entire IPv6 address)
+    # ip_hash;
+    # or "sticky" (needs commercial subscription)
+    # sticky cookie srv_id expires=1h domain=.example.com path=/;
 
     server server-john:3000;
     server server-paul:3000;

examples/cluster-nginx/server/Dockerfile

@@ -1,4 +1,4 @@
-FROM mhart/alpine-node:6
+FROM node:14-alpine
 
 # Create app directory
 RUN mkdir -p /usr/src/app
@@ -6,7 +6,7 @@ WORKDIR /usr/src/app
 
 # Install app dependencies
 COPY package.json /usr/src/app/
-RUN npm install
+RUN npm install --prod
 
 # Bundle app source
 COPY . /usr/src/app