A library that allows easy communication between services via AMQP

Installation

npm install bunny-hole

Intro

This module provides functionality to do RPC via AMQP as well as event handling. RPC is implemented following the mechanisms described in the official RabbitMQ tutorial.

Create an instance of BunnyHole:

new BunnyHole(options [,logger])

If logger is specified it must provide two methods: debug and error.

Example:

const BunnyHole = require('bunny-hole');

let bunnyHole = new BunnyHole(
  {
    host: '127.0.0.1',            // optional, default is '127.0.0.1'
    port: 5672,                   // optional, default is 5672
    username: 'guest',            // optional, default is 'guest'
    password: 'guest',            // optional, default is 'guest',
    eventExchangeName: 'events'   // optional, default is 'events'
  },
  {
    debug: console.log,
    error: console.error
  }
);

Events

The BunnyHole instance will emit a ready event once it is ready to go. If there is an error it will emit an error event.

Register a service

bunnyHole.expose(name, function(params, done) {...} [,parameterSchema])

parameterSchema, if specified, must be a valid JSON Schema. If the incoming parameters don´t match the schema, the request is answered automatically with an error and callback won´t be executed. Validation is done via tv4, so if you need more info on how to use it have a look at the NPM module spec.

Example:

bunnyHole.on('ready', () => {
  bunnyHole.expose('sumObjectProperties', (params, done) => {
    let sum = 0;
    for (let i in params) {
      if (typeof params[i] === 'number') {
        sum += params[i];
      } else {
        return done(new Error('Object contains non-numeric values'));
      }
    }

    done(null, sum);
  });
});

Make an RPC call

bunnyHole.call(name, params [, function(err, result) {...}])

If you don´t expect a result or just want to fire and forget you can omit the callback function parameter.

Example:

bunnyHole.on('ready', () => {
  bunnyHole.call('sumObjectProperties', {a: 1, b: 2, c: 3}, (err, result) => {
    if (err) return console.error('Error in RPC call - ', err);
    console.log('Sum:', result);
  });
});

Listen for events

bunnyHole.listenEvent(name, function (params[, routingKey])) {...} [,groupName] [,queueOptions])

If the groupName parameter is set, the listener will be assigned to a listener pool. Listeners in a pool will be called in a round robin pattern when the event is triggered.

The queueOptions parameter is directly passed through to the creation of the AMQP event queue. See here for further information.

Example:

bunnyHole.on('ready', () => {
  bunnyHole.listenEvent('someEvent', (params) => {
    console.log('Something happened');
  });
});

Emit an event

bunnyHole.emitEvent(name, params)

Example:

bunnyHole.on('ready', () => {
  bunnyHole.emitEvent('someEvent', {foo: 'bar'});
});