Everlution PHP MessageBus

This library provides an eventbus solution in PHP for making microservices interact together.

Installation

As usual just use composer as follows

composer require everlution\message-bus

Components

This library provides default components but you can easily develop your owns by implementing the proper interfaces.

Transport

Must implement Everlution\MessageBus\Transport\TransportInterface.

This component is the actual service that interacts with the "physical" message bus. In other words it is the implementation for using a specific technology.

This library provides already a transport for RabbitMQ Everlution\MessageBus\Transport\RabbitMqTransport using a fanout exchange and re-publishing the message in case of any exception thrown within your consumer.

use PhpAmqpLib\Connection\AMQPStreamConnection;
use Everlution\MessageBus\Transport\RabbitMqTransport;

$connection = new AMQPStreamConnection('rabbitmq_host', 5672, 'user', 'password');
$exchange = 'MessageBus';
$consumerName = 'consumer1';

$transport = new RabbitMqTransport($connection, $exchange, $consumerName);

Message Definition

This is the actual message that will be published on the Transport.

A message can only be an array that will be validated using a JSON Schema definition. In fact the message definition requires you to provide:

• the name of the message (as a discriminator)
• the JSON Schema that validates the message payload itself

The library provides the Everlution\MessageBus\MessageDefinition\PingMessageDefinition for testing purposes.

<?php

class SmsSendMessage implements MessageDefinitionInterface
{
    public static function getName(): string
    {
        return 'sms_send';
    }

    public function getJsonSchema(): string
    {
        $schema = [
            'type' => 'object',
            'properties' => [
                'messageName' => [
                    'type' => 'string',
                    'enum' => [self::getName()],
                ],
                'number' => [
                    'type' => 'string',
                    'regex' => '$\d*^'
                ],
                'text' => [
                    'type' => 'string',
                    'maxLength' => 255,
                ],
            ],
            'additionalProperties' => false,
            'required' => [
                'messageName',
                'number',
                'text',
            ],
        ];

        return json_encode($schema);
    }
}

So in order to define what consumers can publish on the message bus you need to create your messages definitions and then add them to the Protocol.

You can literally shape the message definition as you want as this library doesn't force you to follow any constraint.

Protocol

The Protocol defines in fact the protocol used by all the consumers of the message bus for describing the structure of all the available messages that can be published on the Transport.

A Protocol must implement the $protocol->addMessageDefinition() method that you need to call for every message definition you want to use within your environment.

It basically represents not only a registry of message definitions.

This library provides a default Protocol Everlution\MessageBus\Protocol\DefaultProtocol which basically allows publishers to publish only one of the messages that match one of the message definitions added to the Protocol.

use Everlution\MessageBus\Protocol\DefaultProtocol;

$protocol = new DefaultProtocol();
$protocol->addMessageDefinition(new SmsSendMessage());

Validator

This component is in charge of validating a message against the Protocol.

The Everlution\MessageBus\Validator\DefaultValidator provided uses the Opis\JsonSchema library for that but you can develop your own validation service by implementing Everlution\MessageBus\Validator\ValidatorInterface.

use Everlution\MessageBus\Validator\DefaultValidator;
use Everlution\MessageBus\Validator\ValidatorException;

$validator = new DefaultValidator();

$message = [
    'messageName' => 'sms_send',
    'number' => '0777777777',
    'text' => 'This is my message,
];

try {
    $validator->validate($protocol, $message);
} catch (ValidatorException $e) {
    var_dump($e->getJsonSchema());
    var_dump($e->getData());
    var_dump($e->getErrors());
}

Serializer

The Serializer clearly transforms the message array you want to publish on the Transport into a string and viceversa.

The library provides already the Everlution\MessageBus\Serializer\JsonSerializer.

Publisher

The Publisher must implement Everlution\MessageBus\Publisher\PublisherInterface and its task is to publish the message on the Transport.

The Everlution\MessageBus\Publisher\DefaultPublisher provided does the following steps:

1. validates the message against the Protocol
2. serializes the message
3. publishes the message on the Transport

use Everlution\MessageBus\Publisher\DefaultPublisher;

$publisher = new DefaultPublisher($protocol, $validator, $serializer, $transport);

try {
    $publisher->publish($message);
} catch (\Everlution\MessageBus\Validator\ValidatorException $e) {
    var_dump($e->getJsonSchema());
    var_dump($e->getData());
    var_dump($e->getErrors());
}

Consumer

The Consumer must implement Everlution\MessageBus\Consumer\ConsumerInterface and defines the business logic within your application of how you want to consume messages.

This library provides two consumers.

Echo Consumer

This consumer Everlution\MessageBus\Consumer\EchoConsumer is just for testing purposes and basically does a var_dump(message).

use Everlution\MessageBus\Consumer\EchoConsumer;

$consumer = new EchoConsumer($validator, $protocol, $serializer, $transport);

try {
    $consumer->consume($numberOfMessagesToConsumeAntThenExit = 1);
} catch (\Everlution\MessageBus\Validator\ValidatorException $e) {
    var_dump($e->getJsonSchema());
    var_dump($e->getData());
    var_dump($e->getErrors());
}

Symfony Event Dispatcher Consumer

This consumer Everlution\MessageBus\Consumer\SymfonyEventDispatcherConsumer integrates with Symfony and allows you to transform a normal message into a Symfony Event and dispatch it within your application. In this way you can simply define an event subscriber to that and implement all the logic you need.

This concept decouples the message bus from you application as event subscribers don't who generated the event.

Simulator

It is very likely that if you are using this library you are working with microservices. If this is so you probably don't want to have all the microservices up and running in your local environment in order to generate messages on the bus. On top of that it would be even hard to generate the messages that you need.

The Simulator helps you out as you only need to run locally your microservice and use the Simulator to generate only the messages that you need as if they would come from other sources.

This concept is really useful as it saves you so much time and allows you to concentrate only on that microservice.

This library provides Everlution\MessageBus\Simulator\JsonSchemaFakerSimulator that uses the JSON Schema of the message that you want to simulate and using the Faker library it generates and publish a valid message. This service doesn't cover up all the JSON Schemas you may define but it's a good starting point.

You can extend it or implement your own Simulator by implementing Everlution\MessageBus\Simulator\SimulatorInterface.

Demo

You can find some working examples in /demo.

You can run them using docker with the following commands:

# running composer
./docker/bin/composer.sh "install"

# docker-compose up which spins up rabbitmq etc
./docker/bin/compose/up.sh

# You can ssh in the php-cli container
./docker/bin/ssh.sh php-cli

# You can now run the demo scripts
php demo/ping-publisher.php
php demo/ping-consumer.php

# When you are done tear everything down and destroy all
./docker/bin/compose/down.sh
./docker/bin/compose/rm.sh