MQEmitter RabbitMQ at AMQP protocol

An Opinionated Message Queue with an emitter-style API, but with callbacks.

THIS IS NOT AN OFFICIAL MODULE FROM @mcollina.

If you need a multi process MQEmitter, check out the table below:

• mqemitter: Standard MQemitter
• mqemitter-redis: Redis-powered mqemitter
• mqemitter-mongodb: Mongodb based mqemitter
• mqemitter-child-process: Share the same mqemitter between a hierarchy of child processes
• mqemitter-cs: Expose a MQEmitter via a simple client/server protocol
• mqemitter-p2p: A P2P implementation of MQEmitter, based on HyperEmitter and a Merkle DAG
• mqemitter-aerospike: Aerospike mqemitter

Installation

npm install mqemitter-rabbit

Examples

import { MessageFactory, MQEmitterAMQPLib } from 'mqemitter-rabbit';

const mqemitter = new MQEmitterAMQPLib({
  separator: ':'
});


mqemitter.startConnection(
  {
    url: 'amqps://username:password@hosname/db', // URL of your AMQP instance
    queues: ['entry:message', 'process:message', 'close:message'], // The queues to attach to
    method: ApplicationType.BOTH // Your connection method, must be one of: listener, publisher or both.
  }, 
  (err, cb) => {
    if (err !== undefined) {
      return err;
    }

    cb?.on(
      'conversation:created', (
        message, done
      ) => {
        console.log(
          'Creating new conversation', message
        );

        cb.release(message)
        return done();
      }
    );

    const message = new MessageFactory().generate(
      'conversation:created', // Topic: Required.
      { // Content: aditional content can be attached to the Message.
        user: {
          name: 'Iago Calazans',
          age: 29
        }
      }
    );

    cb?.emit(
      message, // The message itself
      'entry:message', // Queue to publish/emit message
      undefined, // Some headers to attach to Message
      (err) => { // Err callback
        console.log(err); // You can retrieve the errors while trying to attach.
      }
    );
  }
);

new MQEmitterAMQPLib ([options])

• options <object>
  • concurrency <number> maximum number of concurrent messages that can be on concurrent delivery. Default: 0
  • wildcardOne <string> a char to use for matching exactly one non-empty level word. Default: +
  • wildcardSome <string> a char to use for matching multiple level wildcards. Default: #`
  • matchEmptyLevels <boolean> If true then wildcardOne also matches an empty word. Default: true
  • separator <string> a separator character to use for separating words. Default: /

Create a new MQEmitterAMQPLib class.

MQEmitterAMQPLib is the class and function exposed by this module. It can be created by using new MQEmitterAMQPLib({options}).

For more information on wildcards, see this explanation or Qlobber.

emitter.emit (message, callback)

• message <object>
• callback <Function> (error) => void
  • error <Error> | null

Emit the given message, which must have a topic property, which can contain wildcards as defined on creation.

emitter.on (topic, listener, [callback])

• topic <string>
• listener <Function> (message, done) => void
• callback <Function> () => void

Add the given listener to the passed topic. Topic can contain wildcards, as defined on creation.

The listener must never error and done must not be called with an err object.

callback will be called when the event subscribe is done correctly.

emitter.removeListener (topic, listener, [callback])

The inverse of on.

emitter.close (callback)

• callback <Function> () => void

Close the given emitter. After, all writes will return an error.

Wildcards

MQEmitter supports the use of wildcards: every topic is splitted according to separator.

The wildcard character + matches exactly non-empty one word:

emitter.on('hello/+/world', function(message, cb) {
  // will ONLY capture { topic: 'hello/my/world', 'something': 'more' }
  console.log(message)
  cb()
})
emitter.on('hello/+', function(message, cb) {
  // will not be called
  console.log(message)
  cb()
})

const messageComplete = new MessageFactory().generate(
        'hello/my/world', { something: 'more' }
      );
      const messageIncomplete = new MessageFactory().generate(
        'hello//world', { something: 'more' }
      );
emitter.emit(messageComplete)
emitter.emit(messageIncomplete)

The wildcard character + matches one word:

emitter.on('hello/+/world', function(message, cb) {
  // will capture { topic: 'hello/my/world', 'something': 'more' }
  // and capture { topic: 'hello//world', 'something': 'more' }
  console.log(message)
  cb()
})

emitter.on('hello/+', function(message, cb) {
  // will not be called
  console.log(message)
  cb()
})

const messageComplete = new MessageFactory().generate(
        'hello/my/world', { something: 'more' }
      );
      const messageIncomplete = new MessageFactory().generate(
        'hello//world', { something: 'more' }
      );
emitter.emit(messageComplete)
emitter.emit(messageIncomplete)

The wildcard character # matches zero or more words:

emitter.on('hello/#', function(message, cb) {
  // this will print { topic: 'hello/my/world', 'something': 'more' }
  console.log(message)
  cb()
})

emitter.on('#', function(message, cb) {
  // this will print { topic: 'hello/my/world', 'something': 'more' }
  console.log(message)
  cb()
})

emitter.on('hello/my/world/#', function(message, cb) {
  // this will print { topic: 'hello/my/world', 'something': 'more' }
  console.log(message)
  cb()
})

const message = new MessageFactory().generate(
        'hello/my/world', { something: 'more' }
      );
emitter.emit(message)

Of course, you can mix # and + in the same subscription.

LICENSE

ISC