Bowler

A Laravel package that implements the AMQP protocol using the Rabbitmq Server easily and efficiently. Built on top of the php-amqplib, with the aim of providing a simple abstraction layer to work with.

Bowler allows you to:

• Customize message publishing.
• Customize message consumption.
• Customize message dead lettering.
• Handle application errors and deal with the corresponding messages accordingly.
• Provide an expressive consumer queue setup.
• Register a queue and generate it's message handler from the command line.
• Make use of a default Pub/Sub messaging.

In addition to the above Bowler offers limited admin functionalities.

These features will facilitate drastically the way you use Rabbitmq and broaden its functionality. This package do not intend to take over the user's responsability of designing the messaging schema.

Tools like the Rabbitmq Management plugin, will certainly help you monitor the server's activity and visualize the setup.

Installation

Composer

{
    "require": {
        "vinelab/bowler"
    }
}

Usage

Configuration

In order to configure rabbitmq host, port, username, password and configure the timeout and vhost values too, add the following inside the connections array in config/queue.php file:

'rabbitmq' => [
    'host' => 'host',
    'port' => port,
    'username' => 'username',
    'password' => 'password',
    'connection_timeout' => 30,
    'read_write_timeout' => 30,
    'heartbeat' => 15,
    'vhost' => '/',
],

The default value for connection_timeout and read_write_timeout is set to 30 (seconds) and heartbeat is set to 15 (seconds). The vhost value defaults to '/'.

And register the service provider by adding Vinelab\Bowler\BowlerServiceProvider::class to the providers array in config/app.

Producer

In order to be able to send a message, a producer instance needs to be created and an exchange needs to be set up.

// Initialize a Bowler Connection
$connection = new Vinelab\Bowler\Connection();

// Initialize a Producer object with a connection
$bowlerProducer = new Vinelab\Bowler\Producer($connection);

// Setup the producer's exchange name and other optional parameters: exchange type, passive, durable, auto delete and delivery mode
$bowlerProducer->setup('reporting_exchange', 'direct', false, true, false, 2);

// Send a message with an optional routingKey
$bowlerProducer->send($data, 'warning');

or Inject the producer and let the IOC resolve the connection:

use Vinelab\Bowler\Producer;

class DoSomethingJob extends Job
{
    protected $data;

    public function __construct($data)
    {
        $this->data = $data;
    }

    public function handle(Producer $producer)
    {
        $producer->setup('reporting_exchange');

        $producer->send(json_encode($this->data));
    }
}

You need to make sure the exchange setup here matches the consumer's, otherwise a Vinelab\Bowler\Exceptions\DeclarationMismatchException is thrown.

If you mistakenly set an undefined value, setting up the exchange, e.g. $exchangeType='noneExistingType' a Vinelab\Bowler\Exceptions\InvalidSetupException is thrown.

Consumer

Add 'Registrator' => Vinelab\Bowler\Facades\Registrator::class, to the aliases array in config/app.

In order to consume a message an exchange and a queue needs to be set up and a message handler needs to be created.

Configuring the consumer can be done both manually or from the command line:

Manually

1. Register your queues and handlers inside the queues.php file (think about the queues file as the routes file from Laravel), note that the queues.php file should be under App\Messaging directory:

   Registrator::queue('books', 'App\Messaging\Handlers\BookHandler', []);
   
   Registrator::queue('reporting', 'App\Messaging\Handlers\ErrorReportingHandler', [
                                                           'exchangeName' => 'main_exchange',
                                                           'exchangeType'=> 'direct',
                                                           'bindingKeys' => [
                                                               'warning',
                                                               'notification'
                                                           ],
                                                           'pasive' => false,
                                                           'durable' => true,
                                                           'autoDelete' => false,
                                                           'deadLetterQueueName' => 'dlx_queue',
                                                           'deadLetterExchangeName' => 'dlx',
                                                           'deadLetterExchangeType' => 'direct',
                                                           'deadLetterRoutingKey' => 'warning',
                                                           'messageTTL' => null
                                                       ]);

   Use the options array to setup your queues and exchanges. All of these are optional, defaults will apply to any parameters that are not specified here. The descriptions and defaults of these parameters are provided later in this document.

2. Create your handlers classes to handle the received messages:

   //This is an example handler class
   
   namespace App\Messaging\Handlers;
   
   class AuthorHandler {
   
   	public function handle($msg)
   	{
   		echo "Author: ".$msg->body;
   	}
   
       public function handleError($e, $broker)
       {
           if($e instanceof InvalidInputException) {
               $broker->rejectMessage();
           } elseif($e instanceof WhatEverException) {
               $broker->ackMessage();
           } elseif($e instanceof WhatElseException) {
               $broker->nackMessage();
           } else {
               $msg = $borker->getMessage();
               if($msg->body) {
                   //
               }
           }
       }
   }

   Similarly to the above, additional functionality is also provided to the consumer's handler like deleteExchange, purgeQueue and deleteQueue. Use these wisely and take advantage of the unused and empty parameters. Keep in mind that it is not recommended that an application exception be handled by manipulating the server's setup.

Console

Register queues and handlers with php artisan bowler:make:queue analytics_queue AnalyticsData.

The previous command:

1. Adds Registrator::queue('analytics_queue', 'App\Messaging\Handlers\AnalyticsDataHandler', []); to App\Messaging\queues.php.

   If no exchange name is provided the queue name will be used as default.

   The options array, if specified overrides any of the parameters set from the command line. Beside, it serve as a setup reference.

2. Creates the App\Messaging\Handlers\AnalyticsDataHandler.php in App\Messaging\Handlers directory.

Now in order to listen to any queue, run the following command from your console: php artisan bowler:consume analytics_queue. You need to specify the queue name and any other optional parameter, if applicable to your case.

bowler:consume complete arguments list description:

bowler:consume
queueName : The queue NAME
--N|exchangeName : The exchange NAME. Defaults to queueName.
--T|exchangeType : The exchange TYPE. Supported exchanges: fanout, direct, topic. Defaults to fanout.
--K|bindingKeys : The consumer\'s BINDING KEYS array.
--p|passive : If set, the server will reply with Declare-Ok if the exchange and queue already exists with the same name, and raise an error if not. Defaults to 0.
--d|durable : Mark exchange and queue as DURABLE. Defaults to 1.
--D|autoDelete : Set exchange and queue to AUTO DELETE when all queues and consumers, respectively have finished using it. Defaults to 0.
--deadLetterQueueName : The dead letter queue NAME. Defaults to deadLetterExchangeName.
--deadLetterExchangeName : The dead letter exchange NAME. Defaults to deadLetterQueueName.
--deadLetterExchangeType : The dead letter exchange TYPE. Supported exchanges: fanout, direct, topic. Defaults to fanout.
--deadLetterRoutingKey : The dead letter ROUTING KEY.
--messageTTL : If set, specifies how long, in milliseconds, before a message is declared dead letter.

Consuming a none registered queue will throw Vinelab\Bowler\Exceptions\UnregisteredQueueException.

If you wish to handle a message based on the routing key it was published with, you can use a switch case in the handler's handle method, like so:

public function handle($msg)
{
    switch ($msg->delivery_info['routing_key']) {
        case 'key 1': //do something
            break;
        case 'key 2': //do something else
            break;
    }
}

Publish/Subscribe

Bowler provide a default Pub/Sub implementation, where the user doesn't need to care about the setup.

In short, publish with a routingKey and consume with matching bindingKeys.

1. Publish the Message

In your Producer

// Initialize a Bowler object with the rabbitmq server ip and port
$connection = new Bowler\Connection();

// Initialize a Pubisher object with a connection and a routingKey
$bowlerPublisher = new Publisher($connection);

// Publish the message and set its required routingKey
$bowlerPublisher->publish('warning', $data);

Or inject the Publisher similarly to what we've seen [here](### Producer).

As you might have noted, here we instantiate a Publisher not a Producer object. Publisher is a Producer specification, it holds the default Pub/Sub exchange setup.

Signature

publish($routingKey, $data = null);

2. Consume the Message

In your Consumer

i. Register the queue and generate its message handler

In your Consumer; from the command line use the bowler:make:subscriber command.

php artisan bowler:make:subscriber reporting ReportingMessage --expressive

Using the --expressive or -E option will make the queue name reflect that it is used for Pub/Sub. Results in reporting-pub-sub as the generated queue name; otherwise the queue name you provided will be used.

Add the bindingKeys array parameter to the registered queue in queues.php like so:

Registrator::subscriber('reporting-pub-sub', 'App\Messaging\Handlers\ReportingMessageHandler', ['warning']);

ii. Handle messages

Like we've seen [earlier](##### Manually).

iii. Run the queue

From the command line use the bowler:consume command.

php artisan bowler:consume reporting-pub-sub

The Pub/Sub implementation is meant to be used as-is. It is possible to consume all published messages setting the consumer's bindingKeys array to ['*'].

If no bindingKeys are provided a Vinelab\Bowler\Exception\InvalidSubscriberBindingException is thrown.

If you would like to manually do the configuration, you can surely do so by setting up the Producer and Consumer as explained [earlier](## Usage).

Signature

Registrator::subscriber($queue, $className, array $bindingKeys, $exchangeName = 'pub-sub', $exchangeType = 'topic');

Dispatch (Work Queue)

Similar to Pub/Sub, except you may define your own exchange and messages will be distributed according to the least busy consumer (see Work Queue - Fair Dispatch).

1. Dispatch the Message

Dispatch messages on a specific exchange with a routingKey and consumer with matching bindingKeys.

// Initialize a Bowler object with the rabbitmq server ip and port
$connection = new Bowler\Connection();

// Initialize a Dispatcher object with a connection
$dispatcher = new Dispatcher($connection);

// Publish the message and set its required exchange name and routingKey
$dispatcher->dispatch('my-custom-exchange', 'warning', $data);

Signature

dispatch($exchangeName, $routingKey, $data = null, $exchangeType = 'topic')

2. Consume the Message

Registering queue consumers is the same as Pub/Sub, except the exchange name in the registration needs to match.

// catch all the cows in the "farm" exchange
Registrator::subscriber('monitoring', 'App\Messaging\Handlers\MonitoringMessageHandler', [
    '*.cow.*',
], 'farm');

The above will catch all the messages in the farm exchange that match the routing key *.cow.*

Testing

If you would like to silence the Producer/Publisher to restrict it from actually sending/publishing messages to an exchange, bind it to a mock, locally in your test or globally.

Globally: Use Vinelab\Bowler\Publisher in App\Tests\TestCase;

Add the following to App\Tests\TestCase::createApplication():

$app->bind(Publisher::class, function () {
    return $this->createMock(Publisher::class);
});

Dead Lettering

Dead lettering is solely the responsability of the consumer and part of it's queue configuration. Enabeling dead lettering on the consumer is done through the command line using the same command that run the consumer with the dedicated optional arguments or by setting the corresponding optional parameters in the before mentioned, options array. At least one of the --deadLetterQueueName or --deadLetterExchangeName options should be specified.

php artisan bowler:consume my_app_queue --deadLetterQueueName=my_app_dlq --deadLetterExchangeName=dlx --deadLetterExchangeType=direct --deadLetterRoutingKey=invalid --messageTTL=10000

If only one of the mentioned optional parameters are set, the second will default to it. Leading to the same dlx and dlq name.

If you would like to avoid using Dead Lettering, you could leverage a striped down behaviour, by requeueing dead messages using $broker->rejectMessage(true) in the queue's MessageHandler::handleError().

Error Handling

Error Handling in Bowler is limited to application exceptions.

Handler::handleError($e, $broker) allows you to perfom action on the queue. Whether to acknowledge, nacknowledge or reject a message is up to you.

It is not recommended to alter the Rabbitmq setup in reponse to an application exception, e.g. For an InvalidInputException to purge the queue! In nay case, if deemed necessary for the use case, it should be used with caution since you will loose all the queued messages or even worst, your exchange.

While server exceptions will be thrown. Server errors not wrapped by Bowler will be thrown as Vinelab\Bowler\Exceptions\BowlerGeneralException.

Error Reporting

Bowler supports application level error reporting.

To do so, the default laravel exception handler normaly located in app\Exceptions\Handler, should implement Vinelab\Bowler\Contracts\BowlerExceptionHandler. And obviously, implement its method.

ExceptionHandler::reportQueue(Exception $e, AMQPMessage $msg) allows you to report errors as you wish. While providing the exception and the queue message itsef for maximum flexibility.

Health Checks

IMPORTANT: Management plugin is required to be installed in order to perform health checks.

Based on this Reliability Guide, Bowler figured that it would be beneficial to provide a tool to check the health of connected consumers and is provided through the bowler:healthcheck:consumer command with the following signature:

bowler:healthcheck:consumer {queueName : The queue name}

Example: php artisan bowler:healthcheck:consumer the-queue

Will return exit code 0 for success and 1 for failure along with a message why.

Important Notes

1. It is of most importance that the users of this package, take onto their responsability the mapping between exchanges and queues. And to make sure that exchanges declaration are matching both on the producer and consumer side, otherwise a Vinelab\Bowler\Exceptions\DeclarationMismatchException is thrown.

2. The use of nameless exchanges and queues is not supported in this package. Can be reconsidered later.

TODO

• Write tests.
• Become framework agnostic.