How to use redis PUBLISH/SUBSCRIBE with nodejs to notify clients when data values change?
OLD only use a reference
Dependencies
uses express, socket.io, node_redis and last but not least the sample code from media fire.
Install node.js+npm(as non root)
First you should(if you have not done this yet) install node.js+npm in 30 seconds (the right way because you should NOT run npm as root):
echo 'export PATH=$HOME/local/bin:$PATH' >> ~/.bashrc. ~/.bashrcmkdir ~/localmkdir ~/node-latest-installcd ~/node-latest-installcurl http://nodejs.org/dist/node-latest.tar.gz | tar xz --strip-components=1./configure --prefix=~/localmake install # ok, fine, this step probably takes more than 30 seconds...curl http://npmjs.org/install.sh | shInstall dependencies
After you installed node+npm you should install dependencies by issuing:
npm install expressnpm install socket.ionpm install hiredis redis # hiredis to use c binding for redis => FAST :)Download sample
You can download complete sample from mediafire.
Unzip package
unzip pbsb.zip # can also do via graphical interface if you prefer.What's inside zip
./app.js
const PORT = 3000;const HOST = 'localhost';var express = require('express');var app = module.exports = express.createServer();app.use(express.staticProvider(__dirname + '/public'));const redis = require('redis');const client = redis.createClient();const io = require('socket.io');if (!module.parent) { app.listen(PORT, HOST); console.log("Express server listening on port %d", app.address().port) const socket = io.listen(app); socket.on('connection', function(client) { const subscribe = redis.createClient(); subscribe.subscribe('pubsub'); // listen to messages from channel pubsub subscribe.on("message", function(channel, message) { client.send(message); }); client.on('message', function(msg) { }); client.on('disconnect', function() { subscribe.quit(); }); });}./public/index.html
<html><head> <title>PubSub</title> <script src="/socket.io/socket.io.js"></script> <script src="/javascripts/jquery-1.4.3.min.js"></script></head><body> <div id="content"></div> <script> $(document).ready(function() { var socket = new io.Socket('localhost', {port: 3000, rememberTransport: false/*, transports: ['xhr-polling']*/}); var content = $('#content'); socket.on('connect', function() { }); socket.on('message', function(message){ content.prepend(message + '<br />'); }) ; socket.on('disconnect', function() { console.log('disconnected'); content.html("<b>Disconnected!</b>"); }); socket.connect(); }); </script></body></html>Start server
cd pbsb node app.jsStart browser
Best if you start google chrome(because of websockets support, but not necessary). Visit http://localhost:3000 to see sample(in the beginning you don't see anything but PubSub as title).
But on publish to channel pubsub you should see a message. Below we publish "Hello world!" to the browser.
From ./redis-cli
publish pubsub "Hello world!"
here's a simplified example without as many dependencies.You do still need to npm install hiredis redis
The node JavaScript:
var redis = require("redis"), client = redis.createClient();client.subscribe("pubsub");client.on("message", function(channel, message){ console.log(channel + ": " + message);});...put that in a pubsub.js file and run node pubsub.js
in redis-cli:
redis> publish pubsub "Hello Wonky!"(integer) 1which should display: pubsub: Hello Wonky! in the terminal running node!Congrats!
Additional 4/23/2013: I also want to make note that when a client subscribes to a pub/sub channel it goes into subscriber mode and is limited to subscriber commands. You'll just need to create additional instances of redis clients. client1 = redis.createClient(), client2 = redis.createClient() so one can be in subscriber mode and the other can issue regular DB commands.
Complete Redis Pub/Sub Example (Real-time Chat using Hapi.js & Socket.io)
We were trying to understand Redis Publish/Subscribe ("Pub/Sub") and all the existing examples were either outdated, too simple or had no tests.So we wrote a Complete Real-time Chat using Hapi.js + Socket.io + Redis Pub/Sub Example with End-to-End Tests!
The Pub/Sub component is only a few lines of node.js code:https://github.com/dwyl/hapi-socketio-redis-chat-example/blob/master/lib/chat.js#L33-L40
Rather than pasting it here (without any context) we encourage you to checkout/try the example.
We built it using Hapi.js but the chat.js file is de-coupled from Hapi and can easily be used with a basic node.js http server or express (etc.)