orator-dbus/source/Orator-DBUS.js

Orator DBUS queue for RabbitMQ fanout exchange

/**
* Orator DBUS Module
*
* @license All Rights Reserved
*
* @author Jason Hillier <jason.hillier@paviasystems.com>
* @module OratorDBUS
*/

/**
* The Orator DBUS Module
*
* @class OratorDBUS
* @constructor
*/
var OratorDBUS = function()
{
	function createNew(pFable, pRoutingKey)
	{
        // If a valid fable object isn't passed in, return a constructor
		if ((typeof(pFable) !== 'object') || (!pFable.hasOwnProperty('fable')))
			return {new: createNew};
        var _Fable = pFable;
		var _Log = pFable.log;
		var _Settings = pFable.settings;
		var _CommonServices = pFable;

        var libAmqp = require('amqp');
        var _RabbitConnection = null;
        var _RabbitDBUSExchange = null;
        var _RabbitConnected = false;
        var _onMessage_Handler = null;

        if (!pRoutingKey) pRoutingKey = 'base';

        var initializeRabbitMq = function()
		{
			_Log.trace('Connecting to DBUS RabbitMQ at ' + _Settings.RabbitUrl);
            _RabbitConnection = libAmqp.createConnection({url: _Settings.RabbitUrl}, {reconnect: true});

            _RabbitConnection.on('ready', function(hub)
			{
				_RabbitConnected = true;
				_Log.trace('Connected to DBUS RabbitMQ');

				//setup an exchange to send DBUS messages
				_RabbitDBUSExchange = _RabbitConnection.exchange('DBUS', options={type: 'fanout', durable:true, autoDelete:false});

                //setup queue to receive messages
                _RabbitConnection.queue('', function(q)
                {
                    // Catch DBUS messages. (Note: RoutingKey is not used by RabbitMQ in fanout exchanges)
                    q.bind('DBUS', pRoutingKey);

                    // Receive messages 
                    q.subscribe(onDBUS_Message);
                });
			});
        }

        var Publish = function(pFromAddress, pDestinationAddress, pSignal)
        {
            if (!pDestinationAddress || typeof(pDestinationAddress) !== 'string')
            {
                _Log.trace('[DBUS] Invalid destination!');
                return;
            }
            if (_RabbitConnected)
            {
                var tmpMessage = {
                    From: `${pRoutingKey}.${pFromAddress}`,
                    Destination: pDestinationAddress,
                    Signal: pSignal
                };

                _RabbitDBUSExchange.publish(pDestinationAddress, JSON.stringify(tmpMessage), {}, function(err)
                {
                    if (err)
                        _Log.trace('[DBUS] Error sending message', tmpMessage);
                    else
                        _Log.trace('[DBUS] Sent message', tmpMessage);
                });
            }
        }

        var onDBUS_Message = function(pMessage, pHeaders, pDeliveryInfo)
        {
            //only handle messages addressed to our route, or global route
            if (pDeliveryInfo.routingKey !== '' &&
                pDeliveryInfo.routingKey.indexOf(pRoutingKey)!==0)
                return;
            
            //parse utf8
            try
            {
                pMessage = pMessage.data.toString('utf8');
                pMessage = JSON.parse(pMessage)
            } catch (ex)
            {
                _Log.error('[DBUS] Message parsing exception!', ex);
                return;
            }
            //console.log(pDeliveryInfo.routingKey);
            _Log.trace('[DBUS] Received message', pMessage);

            if (_onMessage_Handler)
            {
                var tmpDestinationNode = pDeliveryInfo.routingKey.replace(pRoutingKey + '.', '');
                return _onMessage_Handler(tmpDestinationNode, pMessage);
            }
        }

        // ### Automatically connect the Routes if this is an orator
		if (typeof(pFable.webServer) === 'object')
		{
            initializeRabbitMq();
		}

        /**
		* Container Object for our Factory Pattern
		*/
		var tmpOratorDBUS = (
		{
			new: createNew,
            Publish: Publish
		});

        /**
		 * CommonServices
		 *
		 * @property CommonServices
		 */
		Object.defineProperty(tmpOratorDBUS, 'onMessage',
		{
			get: function() { return _onMessage_Handler; },
            set: function(fMessageHandler) { _onMessage_Handler = fMessageHandler; },
			enumerable: false
		});

		return tmpOratorDBUS;
	}

	return createNew();
};

module.exports = new OratorDBUS();