Transaction-aware Event Dispatcher for Laravel

This Laravel package introduces Transaction-aware Event Dispatcher.
It ensures the events dispatched within a database transaction are dispatched only if the outer transaction successfully commits. Otherwise, the events are discarded and never dispatched.

Note: Laravel 8.17 introduced a new method DB::afterCommit that allows one to achieve the same of this package. Yet, it lacks transaction-aware behavior support for Eloquent events.

Table of Contents

• Motivation
• Installation
  • Laravel
  • Lumen
• Usage
• Configuration
• F.A.Q.

Motivation

Consider the following example of ordering tickets that involves changes to the database.
The orderTickets dispatches the custom OrderCreated event. In turn, its listener sends an email to the user with the order details.

DB::transaction(function() {
    ...
    $order = $concert->orderTickets($user, 3); // internally dispatches 'OrderCreated' event
    PaymentService::registerOrder($order);
});

In the case of transaction failure, due to an exception in the orderTickets method or even a deadlock, the database changes are completely discarded.

Unfortunately, this is not true for the already dispatched OrderCreated event. This results in sending the order confirmation email to the user, even after the order failure.

The purpose of this package is thus to hold events dispatched within a database transaction until it successfully commits. In the above example the OrderCreated event would never be dispatched in the case of transaction failure.

Installation

Laravel

• Install this package via composer:

composer require fntneves/laravel-transactional-events

• Publish the provided transactional-events.php configuration file:

php artisan vendor:publish --provider="Neves\Events\EventServiceProvider"

Lumen

• Install this package via composer:

composer require fntneves/laravel-transactional-events

• Manually copy the provided transactional-events.php configuration file to the config folder:

cp vendor/fntneves/laravel-transactional-events/src/config/transactional-events.php config/transactional-events.php

• Register the configuration file and the service provider in bootstrap/app.php:
  

// Ensure the original EventServiceProvider is registered first, otherwise your event listeners are overriden.
$app->register(App\Providers\EventServiceProvider::class);

$app->configure('transactional-events');
$app->register(Neves\Events\EventServiceProvider::class);

Usage

The transaction-aware layer is enabled out of the box for the events under the App\Events namespace.

This package offers three distinct ways to dispatch transaction-aware events:

• Implement the Neves\Events\Contracts\TransactionalEvent contract;
• Use the generic TransactionalClosureEvent event;
• Use the Neves\Events\transactional helper;
• Change the configuration file.

Use the contract, Luke:

The simplest way to mark events as transaction-aware events is implementing the Neves\Events\Contracts\TransactionalEvent contract:

namespace App\Events;

use Illuminate\Queue\SerializesModels;
use Illuminate\Foundation\Events\Dispatchable;
...
use Neves\Events\Contracts\TransactionalEvent;

class TicketsOrdered implements TransactionalEvent
{
    use Dispatchable, InteractsWithSockets, SerializesModels;

    ...
}

And that's it. There are no further changes required.

What about Jobs?

This package provides a generic TransactionalClosureEvent event for bringing the transaction-aware behavior to custom behavior without requiring specific events.

One relevant use case is to ensure that Jobs are dispatched only after the transaction successfully commits:

DB::transaction(function () {
    ...
    Event::dispatch(new TransactionalClosureEvent(function () {
        // Job will be dispatched only if the transaction commits.
        ProcessOrderShippingJob::dispatch($order);
    });
    ...
});

And that's it. There are no further changes required.

Configuration

The configuration file includes the following parameters:

Enable or disable the transaction-aware behavior:

'enable' => true

By default, the transaction-aware behavior will be applied to all events under the App\Events namespace.
Feel free to use patterns and namespaces.

'transactional' => [
    'App\Events'
]

Choose the events that should always bypass the transaction-aware layer, i.e., should be handled by the original event dispatcher. By default, all *ed Eloquent events are excluded. The main reason for this default value is to avoid interference with your already existing event listeners for Eloquent events.

'excluded' => [
    // 'eloquent.*',
    'eloquent.booted',
    'eloquent.retrieved',
    'eloquent.saved',
    'eloquent.updated',
    'eloquent.created',
    'eloquent.deleted',
    'eloquent.restored',
],

Frequently Asked Questions

Can I use it for Jobs?

Yes. As mentioned in Usage, you can use the generic TransactionalClosureEvent(Closure $callable) event to trigger jobs only after the transaction commits.

License

This package is open-sourced software licensed under the MIT license.