php-event-pubsub

An event protocol and implementation over pub/sub

This library builds on top of the php-pubsub package and adds support for listening to and dispatching events over pub/sub channels.

Installation

composer require superbalist/php-event-pubsub

Integrations

Want to get started quickly? Check out some of these integrations:

• Laravel - https://github.com/Superbalist/laravel-event-pubsub

Usage

Simple Events

A SimpleEvent is an event which takes a name and optional attributes.

// create a new event manager
$adapter = new \Superbalist\PubSub\Adapters\LocalPubSubAdapter();
$translator = new \Superbalist\EventPubSub\Translators\SimpleEventMessageTranslator();
$manager = new \Superbalist\EventPubSub\EventManager($adapter, $translator);

// dispatch an event
$event = new \Superbalist\EventPubSub\Events\SimpleEvent(
    'user.created',
    [
        'user' => [
            'id' => 1456,
            'first_name' => 'Joe',
            'last_name' => 'Soap',
            'email' => '[email protected]',
        ],
    ]
);
$manager->dispatch('events', $event);

// dispatch multiple events
$events = [
    new \Superbalist\EventPubSub\Events\SimpleEvent(
        'user.created',
        [
            'user' => [
                // ...
            ],
        ]
    ),
    new \Superbalist\EventPubSub\Events\SimpleEvent(
        'user.created',
        [
            'user' => [
                // ...
            ],
        ]
    ),
];
$manager->dispatchBatch('events', $events);

// listen for an event
$manager->listen('events', 'user.created', function (\Superbalist\EventPubSub\EventInterface $event) {
    var_dump($event->getName());
    var_dump($event->getAttribute('user'));
});

// listen for all events on the channel
$manager->listen('events', '*', function (\Superbalist\EventPubSub\EventInterface $event) {
    var_dump($event->getName());
});

Topic Events

A TopicEvent is an event which takes a topic, name, version and optional attributes.

// create a new event manager
$adapter = new \Superbalist\PubSub\Adapters\LocalPubSubAdapter();
$translator = new \Superbalist\EventPubSub\Translators\TopicEventMessageTranslator();
$manager = new \Superbalist\EventPubSub\EventManager($adapter, $translator);

// dispatch an event
$event = new \Superbalist\EventPubSub\Events\TopicEvent(
    'user',
    'created',
    '1.0',
    [
        'user' => [
            'id' => 1456,
            'first_name' => 'Joe',
            'last_name' => 'Soap',
            'email' => '[email protected]',
        ],
    ]
);
$manager->dispatch('events', $event);

// listen for an event on a topic
$manager->listen('events', 'user/created', function (\Superbalist\EventPubSub\EventInterface $event) {
    // ...
});

// listen for an event on a topic matching the given version
$manager->listen('events', 'user/created/1.0', function (\Superbalist\EventPubSub\EventInterface $event) {
    // ...
});

// listen for all events on a topic
$manager->listen('events', 'user/*', function (\Superbalist\EventPubSub\EventInterface $event) {
    // ...
});

// listen for all events on the channel
$manager->listen('events', '*', function (\Superbalist\EventPubSub\EventInterface $event) {
    // ...
});

Schema Events

A SchemaEvent is an extension of the TopicEvent and takes a schema and optional attributes. The topic, name and version are derived from the schema.

The schema must be in the format (protocol)://(......)?/events/(topic)/(channel)/(version).json

// create a new event manager
$adapter = new \Superbalist\PubSub\Adapters\LocalPubSubAdapter();

$translator = new \Superbalist\EventPubSub\Translators\SchemaEventMessageTranslator();

$schemas = [
    'events/user/created/1.0.json' => json_encode([
        '$schema' => 'http://json-schema.org/draft-04/schema#',
        'title' => 'My Schema',
        'type' => 'object',
        'properties' => [
            'schema' => [
                'type' => 'string',
            ],
            'user' => [
                'type' => 'object',
            ],
        ],
        'required' => [
            'schema',
            'user',
        ],
    ]),
];
$loader = new \League\JsonGuard\Loaders\ArrayLoader($schemas);

$dereferencer = new \League\JsonGuard\Dereferencer();
$dereferencer->registerLoader($loader, 'array');

$validator = new \Superbalist\EventPubSub\Validators\JSONSchemaEventValidator($dereferencer);

$manager = new \Superbalist\EventPubSub\EventManager($adapter, $translator, $validator);

// dispatch an event
$event = new \Superbalist\EventPubSub\Events\SchemaEvent(
    'http://schemas.my-website.org/events/user/created/1.0.json',
    [
        'user' => [
            'id' => 1456,
            'first_name' => 'Joe',
            'last_name' => 'Soap',
            'email' => '[email protected]',
        ],
    ]
);
$manager->dispatch('events', $event);

// the listen expressions are the same as those used for TopicEvents.

Custom Events

You can easily use a custom event structure by writing a class which implements the EventInterface interface. You will then need to write a custom translator to translate incoming messages to your own event object.

Your event must implement the following methods.

/**
 * Return the event name.
 *
 * @return string
 */
public function getName();

/**
 * Return all event attributes.
 *
 * @return array
 */
public function getAttributes();

/**
 * Return an event attribute.
 *
 * @param string $name
 * @return mixed
 */
public function getAttribute($name);

/**
 * Set an event attribute.
 *
 * @param string|array $name
 * @param mixed $value
 */
public function setAttribute($name, $value = null);

/**
 * Check whether or not an event has an attribute.
 *
 * @param string $name
 * @return bool
 */
public function hasAttribute($name);

/**
 * Check whether or not the event matches the given expression.
 *
 * @param string $expr
 * @return bool
 */
public function matches($expr);

/**
 * Return the event in a message format ready for publishing.
 *
 * @return mixed
 */
public function toMessage();

Translators

A translator is used to translate an incoming message into an event.

The package comes bundled with a SimpleEventMessageTranslator, TopicEventMessageTranslator and a SchemaEventMessageTranslator.

Custom Translators

You can easily write your own translator by implementing the MessageTranslatorInterface interface.

Your translator must implement the following methods.

/**
 * @param mixed $message
 * @return null|EventInterface
 */
public function translate($message);

Validators

A validator is an optional component used to validate an event upon dispatch.

JSONSchemaEventValidator

This package comes bundled with a JSONSchemaEventValidator which works with SchemaEvent type events.

This validator validates events against a JSON Schema Spec using the JSON Guard PHP package.

Please see the "Schema Events" section above and the JSON Guard documentation for usage examples.

Custom Validators

You can write your own validator by implementing the EventValidatorInterface interface.

Your validator must implement the following methods.

/**
 * @param EventInterface $event
 * @return ValidationResult
 */
public function validate(EventInterface $event);

Attribute Injectors

An attribute injector allows you to have attributes automatically injected into events when events are dispatched.

The library comes bundled with a few injectors out of the box.

• DateAttributeInjector - injects a date key with an ISO 8601 date time
• GenericAttributeInjector - injects a custom key and value
• HostnameAttributeInjector - injects a hostname key with the server hostname
• Uuid4AttributeInjector - injects a uuid key with a UUID-4

You can write your own injector by implementing the AttributeInjectorInterface or by passing a callable (which returns an array with a 'key' and 'value') to the event manager.

Your injector must implement the following methods.

/**
 * @return string
 */
public function getAttributeKey();

/**
 * @return mixed
 */
public function getAttributeValue();

Here's a usage example demonstrating both a class and a callable.

Custom Class

use Superbalist\EventPubSub\AttributeInjectorInterface;

class UserAttributeInjector implements AttributeInjectorInterface
{
    /**
     * @return string
     */
    public function getAttributeKey()
    {
        return "user";
    }

    /**
     * @return mixed
     */
    public function getAttributeValue()
    {
        return [
            'id' => 2416334,
            'email' => '[email protected]',
            'first_name' => 'John',
            'last_name' => 'Doe',
        ];
    }
}

// create a new event manager
$adapter = new \Superbalist\PubSub\Adapters\LocalPubSubAdapter();
$translator = new \Superbalist\EventPubSub\Translators\SimpleEventMessageTranslator();
$manager = new \Superbalist\EventPubSub\EventManager($adapter, $translator);

$manager->addAttributeInjector(new UserAttributeInjector());

// or
$manager = new \Superbalist\EventPubSub\EventManager($adapter, $translator, null, [new UserAttributeInjector()]);

Callable

// create a new event manager
$adapter = new \Superbalist\PubSub\Adapters\LocalPubSubAdapter();
$translator = new \Superbalist\EventPubSub\Translators\SimpleEventMessageTranslator();
$manager = new \Superbalist\EventPubSub\EventManager($adapter, $translator);

$manager->addAttributeInjector(function () {
    return [
        'key' => 'user',
        'value' => [
            'id' => 2416334,
            'email' => '[email protected]',
            'first_name' => 'John',
            'last_name' => 'Doe',
        ],
    ];
});

Error Handling

The library supports error handlers for when event translation fails, listen expression fails and validation fails.

You can pass callables into the EventManager constructor, or set them as follows:

// create a new event manager
$adapter = new \Superbalist\PubSub\Adapters\LocalPubSubAdapter();
$translator = new \Superbalist\EventPubSub\Translators\SimpleEventMessageTranslator();
$manager = new \Superbalist\EventPubSub\EventManager($adapter, $translator);

// hook into translation failures
$manager->setTranslateFailHandler(function ($message) {
    // the message failed to translate into an event
});

// hook into listen expression failures
$manager->setListenExprFailHandler(function (\Superbalist\EventPubSub\EventInterface $event, $expr) {
    // the event didn't match the listen expression
    // this isn't really an error, but can be useful for debug
});

// hook into validation failures
$manager->setValidationFailHandler(function (\Superbalist\EventPubSub\ValidationResult $result) {
    // the event failed validation
    var_dump($result->errors());
});

Examples

The library comes with examples for the different types of events and a Dockerfile for running the example scripts.

Run make up.

You will start at a bash prompt in the /opt/php-event-pubsub directory.

To run the examples:

$ php examples/SimpleEventExample.php
$ php examples/TopicEventExample.php
$ php examples/SchemaEventExample.php