lapin

Lapin wrapper for RabbitMQ

Currently this project is using Rabbus and Rabbot. Wascally can also be used instead of rabbot. This project is aiming to support several producer / consumer patterns. The following are is a list of the planned patterns, and the checked ones are currently implemented:

• Send / Receive
• Publish / Subscribe
• Request / Response

The JSend specification is required to determine if an error has occurred in a response.

Installation and Usage

As lapin uses rabbot you need to install it along with lapin:

npm install rabbot
npm install lapin

Require lapin and rabbot:

const rabbit = require( 'rabbot' );
const lapin  = require( 'lapin' )( rabbit );

// or

const options = {
	logger, rabbit
};

const lapin = require( 'lapin' )( options )

The following are simple usage examples:

Send / Receive

Sender Options

exchange, messageType, routingKey, autoDelete

Please refer to Rabbus options' info

Sender

options = 'v1.logs.log';
// or
options = {
    'messageType' : 'v1.logs.log',
    'exchange'    : 'logs'
}
lapin.send( options , message, function ( error, response ) {

	// handling the response is optional
	if ( !error ) {
		console.log( response );
	}

} );

Or use the promise style send

lapin.sendPromise( 'v1.logs.log', message )
	.then( function ( response ) {
		// Return for chain then and handle response
		console.log( response );

	} )
	.catch( function ( error ) {
		// Handler error
	} );

Receiver Options

queue, exchange, messageType, autoDelete, limit, noBatch

Receiver

options = 'v1.logs.log';
// or
options = {
    'messageType' : 'v1.logs.log',
    'exchange'    : logs
}

lapin.receive( options, function ( message, send ) {

	someDatabaseQuery( message, function ( err, body ) {
		// See # Return Status for send object usage
	} );

} );

Publish / Subscribe

Publisher Options

exchange, messageType, autoDelete

Publisher

options = 'v1.users.login';
// or
options = {
    'messageType' : 'v1.users.login',
    'exchange'    : 'users' // recommended not to prefix or suffix `exchange` lapin will do it for us
}
lapin.publish( options, message, function ( error, response ) {

		// handling the response is optional
	if ( !error ) {
		console.log( response );
	}

} );

Subscriber Options

queue, exchange, messageType, autoDelete, limit, noBatch

Subscriber

options = 'v1.users.login';
// or
options = {
    'messageType' : 'v1.users.login',
    'queue'       : 'users' // recommended not to put `queue` suffix or prefix, lapin will do it for you
    'exchange'    : 'users'
}
lapin.subscribe( options, function ( message, done ) {

	someDatabaseQuery( message, function ( err, body ) {

		if ( err ) {
			throw err;
		}

		done();

	} );

} );

Request / Response

Request Options

exchange, messageType, autoDelete, routingKey, forceAck

Requester

options = 'v1.users.findAll'
// or
options = {
    'messageType' : 'v1.users.findAll',
    'exchange'    : 'users'
}
lapin.request( options, message, function ( error, data ) {

	if ( error ) {
		return reply( error ).code( 500 );
	}

	return reply( data.data );
} );

Or use the promise style request

lapin.requestPromise( 'v1.users.findAll', message )
	.then( function ( data ) {
		// Handle data
		return reply( data.data );

	} )
	.catch( function ( error ) {
		// Handle error
	} );

Responder Options

exchange, queue, autoDelete, routingKey, limit, noBatch

Responder

options = 'v1.users.findAll';
// or
options = {
    'messageType' : 'v1.users.findAll',
    'limit'       : 1
}
lapin.respond( options, function ( message, send ) {
	// See # Return Status for send object usage
} );

Response with Validation using Joi

// Responder
lapin.respond( {
    'messageType' : 'v1.users.findAll',
    'validate'    : Joi.object().keys( {
  		'username'     : Joi.string().alphanum().min( 3 ).max( 30 ).required(),
  		'password'     : Joi.string().regex( /[a-zA-Z0-9]{3,30}/ ),
  		'access_token' : [ Joi.string(), Joi.number() ],
  		'birthyear'    : Joi.number().integer().min( 1900 ).max( 2013 ),
  		'email'        : Joi.string().email()
  	} ).with( 'username', 'birthyear' ).without( 'password', 'access_token' ),

    'validateOptions' : {} // <optional> see https://github.com/hapijs/joi for validation options

} , function ( message, send ) {
	// See # Return Status for send object usage
} );

If validation fails, lapin will bypass respond callback and response a fail status as seen below:

    respond( {
        'status' : 'fail',
        'data'   : <Validation error message>
    } );

Please refer to Joi Validation for validation examples, structure and validation options

To Consider

Make sure to use the same messageType, routingKey and exchange options. Whenever a String option is supplied instead of the Object option, lapin will automatically create the ff:

• exchange and messageType ( Producer )
• exchange, messageType and queue ( Consumer )

Return Status

The following consumers returns an object status

• Responder ( Req-Res )
• Receiver ( Send-Rec )

lapin.[ respond | receive ] ( message, send ) {

}

where send is an object of return status

send = {
	'success' : {
		returns {
			'status' : success,
			'data'   : data
		},

		'fail' : {
			returns {
				'status' : 'fail',
				'data'   : errorData
		},

		'error' : {
			return {
				'status'  : 'error',
				'message' : errorMsg,
				'data'    : errorData,
				'code'    : errorCode
			}
		}
}

Return Status Usage

lapin.[ respond | receive ]( options, function ( message, send ) {

	if ( message.invalid ) {
			return send.fail( 'Invalid data' );
	}

	someDatabaseQuery().then( function ( result ) {

		// JSend success with data
		send.success( result );

	} ).catch( function handleError ( error ) {

		// JSend error
		send.error( 'Failed query', error, 500 );
		// or -- code is optional
		send.error( 'Failed query', error );
		// or -- data is optional
		send.error( 'Failed query' );

	} );

} );

Please refer to JSEND for standard reply attributes

Contributing

All pull requests must follow coding conventions and standards.

Additional Information

RPC over RabbitMQ

In general, doing RPC over RabbitMQ is easy. A client sends a request message and a server replies with a response message. In order to receive a response the client needs to send a 'callback' queue address with the request.

• When the client starts up, it creates an exclusive callback queue.
• For an RPC request, the Client sends a message with two required properties: reply_to, which is set to the callback queue and correlation_id, which is set to a unique value for every request.
• The request is sent to an rpc_queue queue.
• The RPC worker (aka: server) is waiting for requests on that queue. When a message appears, it does the job and sends a message with the result back to the Client, using the queue from the reply_to field.
• The client waits for data on the callback queue. When a message appears, it checks the correlation_id property. If it matches the value from the request it returns the response to the application.

Standards/Conventions

• messageType: <version>.<resource>.<action>

• exchange: <pattern>.<resource>-exchange

• queue: <pattern>.-queue

Where

Patterns:

• req-res

• pub-sub

• send-rec

Version:

• v1

• v2

• and so on.