publish-subscribe.md

Publish / Subscribe

Note: Currently, a messageType is required for Pub/Sub.

The Publish / Subscribe object pair uses a fanout exchange inside of RabbitMQ, allowing you to have as many subscribers as you need. Think of pub/sub as an event that gets broadcast to anyone that cares, or no one at all if no one is listening.

Set Up A Publisher

// define a publisher
// ------------------

var util = require("util");
var Rabbus = require("rabbus");
var rabbot = require("rabbot");

function SomePublisher(){
  Rabbus.Publisher.call(this, rabbot, {
    exchange: "pub-sub.exchange",
    routingKey: "pub-sub.key"
  });
}

util.inherits(SomePublisher, Rabbus.Publisher);

// publish a message
// -----------------

var publisher = new SomePublisher();

var message = {
  place: "world"
};

publisher.publish(message, function(){
  console.log("published a message");
});

Publisher Options

The following options are available when configuring a publisher:

• exchange (string): name of the exchange to create and publish to
• exchange (object): object literal with options for the exchange
  • name (string): name of the exchange to create and publish to
  • type (string): type of exchange to use. default is fanout.
  • autoDelete (boolean): delete this exchange when there are no more connections using it. default is false.
  • durable (boolean): this exchange will survive a shut down / restart of RabbitMQ. default is true.
  • persistent (boolean): messages published through this exchange will be saved to disk / survive restart of RabbitMQ. default is true.
• messageType (string): optional the type of message being published. (See below.)
• routingKey (string): the routing key to use for the published message

Set Up A Subscriber

// define a subscriber
// -------------------

var util = require("util");
var Rabbus = require("rabbus");
var rabbot = require("rabbot");

function SomeSubscriber(){
  Rabbus.Subscriber.call(this, rabbot, {
    exchange: "pub-sub.exchange",
    queue: "pub-sub.queue",
    routingKey: "pub-sub.key"
  });
}

util.inherits(SomeSubscriber, Rabbus.Subscriber);

// subscribe to a message
// ----------------------

var sub1 = new SomeSubscriber();
sub1.subscribe(function(message, properties, actions, next){
  console.log("1: hello", message.place);
  actions.ack();
});

var sub2 = new SomeSubscriber();
sub2.subscribe(function(message, properties, actions, next){
  console.log("2: hello", message.place);
  actions.ack();
});

var sub3 = new SomeSubscriber();
sub3.subscribe(function(message, properties, actions, next){
  console.log("3: hello", message.place);
  actions.ack();
});

Subscriber Options

See Publisher options for Exchange definition. The exchange and queue that you specify in these options will be used to create the binding between the exchange and queue.

• exchange: (see Publisher for options)
• queue (string): name of the queue to create and subscribe to
• queue (object): object literal with options for the queue
  • name (string): name of the queue to create and subscriber to
  • autoDelete (boolean): delete this queue when there are no more connections using it. default is false.
  • durable (boolean): this queue will survive a shut down / restart of RabbitMQ. default is true.
• messageType (string): optional the type of message to handle for this subscriber instance. (See below.)
• routingKey (string): the routing key to use for binding the exchange and queue
• routingKey ([string]): an array of string for the routing key to use for binding the exchange and queue