Messaging with node.js and RabbitMQ

This library implements messaging patterns in node.js), using RabbitMQ.

You can use it as a gateway between socket servers in node.js (e.g., Socket.IO or net.Server) and RabbitMQ, or as an intermediary for sockets.

As an example of the first, you might use it to distribute events from a backend system, through RabbitMQ, to browser clients.

As an example of the second, you might use it to allow browser clients to communicate among themselves.

There are three messaging patterns supported, following ZeroMQ and the RabbitMQ/ZeroMQ bridge:

• publish/subscribe: pub sockets publish to a rendezvous point; all sub sockets connected to the rendezvous point receive the messages.

• request/reply: req sockets send requests to a rendezvous point, which are distributed among the rep sockets connected to the rendezvous point. The replies back through the rep sockets are routed back to the originating req sockets.

• push/pull: push sockets send messages to a rendezvous point; the messages are distributed among the pull sockets connected to the rendezvous point.

(Skip to "Getting it running")

MessageStream and MessageServer

These classes are used to decorate byte streams (e.g., net.Stream) and servers (e.g., net.Server) respectively. MessageStream simply partitions a byte stream into length-prefixed messages. MessageServer wraps a server to provide MessageStreams instead of streams for connections.

Sockets

The module sockets.js wraps a message server to speak the messaging patterns using RabbitMQ. The file socketserver.js shows how to do this with a regular net.Server by wrapping it first in a MessageServer, then using sockets.listen();

The sockets need a tiny bit of protocol on connection; the first message sent must be the intended socket type -- one of 'pub', 'sub', 'push', 'pull', 'req', 'rep' -- plus a space, plus the name of a "rendezvous point" (which will correspond to an AMQP exchange or queue). For example, "pub amq.topic". The rendezvous point will be created for you if necessary.

The rendezvous is optional for pub and sub sockets, which will use the amq.fanout exchange by default (but it is better to provide one, unless you want all messages from all pub sockets going to all subscribed sockets).

You can supply another argument to sockets.listen, which will be used for access control. It is simply a map of rendezvous names to allowed socket types; e.g.,

{'chat': ['pub', 'sub'],
 'requests': ['req', 'rep']}

You can interact with the socketserver via MessageStreams. Run the socketserver:

$ node socketserver.js

then from another shell start node and create a couple of sockets:

$ node
> var msg = require('./messages'), net = require('net');
> s1 = new msg.MessageStream(net.createConnection(9000));
> s1.send('pub');
> s2 = new msg.MessageStream(net.createConnection(9000));
> s2.send('sub');
> s2.on('message', function(m) { console.log(m.toString()); });
> s1.send('Hello world!');

Pipes

sockets.Server is a server with a method for getting a connection to it. This is useful if you want to program with sockets from inside node.

$ node
> var socks = new require('./sockets');
> var serv = new socks.Server();
> socks.listen(serv); // the ff not a callback for readability
> var pub = serv.connect();
> pub.send('pub');
> var sub = serv.connect();
> sub.send('sub');
> sub.on('message', function(m) {console.log(m);});
> pub.send('Hello world!');

rabbit.js and Socket.IO

MessageStream is designed to look just like Socket.IO's Client class, and sockets.listen() will happily wrap a Socket.IO server. npm should install Socket.IO; or, install using

$ npm bundle install socket.io

Then run node socketio.js, and point your browser at http://localhost:8080/ you'll get a familiar demo, this time running through RabbitMQ.

You can also mix this with the socket or pipe server above, since they are both sending messages through RabbitMQ; or, with an AMQP client (note -- the pub/sub sockets use the exchange amq.fanout by default).

Getting it running

For the minute you need my fork of node-amqp:

rabbit.js$ npm bundle install https://github.com/squaremo/node-amqp/tarball/master

You also need RabbitMQ, of course. Follow the installation instructions, or if you use homebrew just do

$ brew install rabbitmq
...
$ rabbitmq-server