What's the most efficient node.js inter-process communication library/method?

Question

We have few node.js processes that should be able to pass messages, What's the most efficient way doing that? How about using node_redis pub/sub

EDIT: the processes might run on different machines

Answer 1

If you want to send messages from one machine to another and do not care about callbacks then Redis pub/sub is the best solution. It's really easy to implement and Redis is really fast.

First you have to install Redis on one of your machines.

Its really easy to connect to Redis:

var client = require('redis').createClient(redis_port, redis_host);

But do not forget about opening Redis port in your firewall!

Then you have to subscribe each machine to some channel:

client.on('ready', function() {
  return client.subscribe('your_namespace:machine_name');
});

client.on('message', function(channel, json_message) {
  var message;
  message = JSON.parse(message);
  // do whatever you vant with the message
});

You may skip your_namespace and use global namespace, but you will regret it sooner or later.

It's really easy to send messages, too:

var send_message = function(machine_name, message) {
  return client.publish("your_namespace:" + machine_name, JSON.stringify(message));
};

If you want to send different kinds of messages, you can use pmessages instead of messages:

client.on('ready', function() {
  return client.psubscribe('your_namespace:machine_name:*');
});

client.on('pmessage', function(pattern, channel, json_message) {
  // pattern === 'your_namespace:machine_name:*'
  // channel === 'your_namespace:machine_name:'+message_type
  var message = JSON.parse(message);
  var message_type = channel.split(':')[2];
  // do whatever you want with the message and message_type
});

send_message = function(machine_name, message_type, message) {
  return client.publish([
    'your_namespace',
    machine_name,
    message_type
  ].join(':'), JSON.stringify(message));
};

The best practice is to name your processes (or machines) by their functionality (e.g. 'send_email'). In that case process (or machine) may be subscribed to more than one channel if it implements more than one functionality.

Actually, it's possible to build a bi-directional communication using redis. But it's more tricky since it would require to add unique callback channel name to each message in order to receive callback without losing context.

So, my conclusion is this: Use Redis if you need "send and forget" communication, investigate another solutions if you need full-fledged bi-directional communication.