ICQueue

Simple consuming and publishing from/to RabbitMQ.

Declarative API to consume from a rabbitMQ queue and to perform publish operations.

• Auto queue declaration & binding
• Dead lettering support
• Easy publishing
• Simple promise based API

Example usage

const ICQueue = require('icqueue');

var config = {
  url: process.env.AMQP_URL,
  exchange: process.env.AMQP_EXCHANGE,
  queue: {
    name: process.env.AMQP_CONSUME,
    routingKey: process.env.AMQP_ROUTING_KEY, // If supplied, queue is bound to
    // this key (or keys) on the exchange. NB Can be an array of strings or just
    // a string.
    options: {/* ... */} // Advanced: options passed to ch.assertQueue() in wrapped `amqplib`.
  },
  // Set the QOS/prefetch (defaults to 1)
  prefetch: 100
};

const icq = new ICQueue(config);

async function main () {
  // Must call this before you consume/publish/etc...
  await icq.connect();

  // Consuming
  var handleMessage = function(message, callback) {
    //... Do things
    callback();
  };
  // You must call:
  callback(err, requeue)
  // in your handleMessage. If `err` !== `null` then the message will be `nack`ed.
  // Requeueing will be requeue iff `requeue` is `true`.
  // If `err` is `null` then the message is `ack`ed.
  // If an exception occurs in handleMessage, then the message is `nack`ed and not requeued.

  // Start consuming:
  icq.consume(handleMessage);

  // Publishing to arbitrary routing key.
  await icq.publish(routingKey, payload, options);
}

If payload is an object, it will be turned into JSON.

Details

This is a wrapper to https://github.com/squaremo/amqp.node (amqplib).

• You can specify a queue which will be declared (made to exist). This will be the queue from which you will consume.
• If you specify a routing key for the queue, then a binding will be set up (I.e. a mapping that tells AMQP to route message with that routing key to that queue on the exchange you have specified).
• Any options you specify at the per-queue level are passed directly through to ch.assertQueue in the underlying library. If you want to set up dead lettering, for example, then pass the deadLetterExchange option which will cause the queue to be declared with that dead letter exchange.
• deadLetterExchange and deadLetterRoutingKey are special options, in that as well as being passed through to ch.assertQueue() to ensure the dead lettering behaviour occurs, a queue will be declared of the same name with the -dead-letter suffix, with a binding declared on the dead letter exchange for the dead letter routing key. This means that when a message is dead lettered on that queue it will have somewhere to go without you having to set up a dead lettering queue manually.

Tests

Start a rabbit server, preferably a 'throw away' one with fresh state. You can do this like so if you have docker:

docker run -d --rm -p 5672:5672 rabbitmq

Wait for it to finish starting up, then:

npm test

Note that tests/config.js currently assumes you are using boot2docker (on a Mac) so you may need to hack that stuff (or it may just work as it should just use localhost if it's not there... unproven though.)

API

ICQueue

Class to contain an instantiated connection/channel to AMQP with a given config.

Kind: global class

• ICQueue
  • new ICQueue(config)
  • .connect() ⇒ Promise
  • .close() ⇒ Promise
  • .publish(routingKey, message, options) ⇒ Promise
  • .consume(handleMessage, options) ⇒ Promise

new ICQueue(config)

Instantiate an AMQP wrapper with a given config.

icqueue.connect() ⇒ Promise

Connects, establishes a channel, sets up exchange/queues/bindings/dead lettering.

Kind: instance method of ICQueue

icqueue.close() ⇒ Promise

Closes connection.

Kind: instance method of ICQueue

icqueue.publish(routingKey, message, options) ⇒ Promise

Publish a message to the given routing key, with given options.

Kind: instance method of ICQueue

icqueue.consume(handleMessage, options) ⇒ Promise

handleMessage() is expected to be of the form: handleMessage(parsedMessage, callback). If callback is called with a non-null error, then the message will be nacked. You can call it like: callback(err, requeue) in order to instruct rabbit whether to requeue the message (or discard/dead letter).

If not given, requeue is assumed to be false.

cf http://squaremo.github.io/amqp.node/doc/channel_api.html#toc_34

Kind: instance method of ICQueue