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Laravel 5.4

Queues

Introduction

Laravel queues provide a unified API across a variety of different queue backends, such as Beanstalk, Amazon SQS, Redis, or even a relational database. Queues allow you to defer the processing of a time consuming task, such as sending an email, until a later time. Deferring these time consuming tasks drastically speeds up web requests to your application.

The queue configuration file is stored in config/queue.php. In this file you will find connection configurations for each of the queue drivers that are included with the framework, which includes a database, Beanstalkd, Amazon SQS, Redis, and a synchronous driver that will execute jobs immediately (for local use). A null queue driver is also included which simply discards queued jobs.

Connections Vs. Queues

Before getting started with Laravel queues, it is important to understand the distinction between “connections” and “queues”. In your config/queue.php configuration file, there is a connections configuration option. This option defines a particular connection to a backend service such as Amazon SQS, Beanstalk, or Redis. However, any given queue connection may have multiple “queues” which may be thought of as different stacks or piles of queued jobs.

Note that each connection configuration example in the queue configuration file contains a queue attribute. This is the default queue that jobs will be dispatched to when they are sent to a given connection. In other words, if you dispatch a job without explicitly defining which queue it should be dispatched to, the job will be placed on the queue that is defined in the queue attribute of the connection configuration:

// This job is sent to the default queue...
dispatch(new Job);
// This job is sent to the "emails" queue...
dispatch((new Job)->onQueue('emails'));

Some applications may not need to ever push jobs onto multiple queues, instead preferring to have one simple queue. However, pushing jobs to multiple queues can be especially useful for applications that wish to prioritize or segment how jobs are processed, since the Laravel queue worker allows you to specify which queues it should process by priority. For example, if you push jobs to a high queue, you may run a worker that gives them higher processing priority:

php artisan queue:work --queue=high,default

Driver Prerequisites

Database

In order to use the database queue driver, you will need a database table to hold the jobs. To generate a migration that creates this table, run the queue:table Artisan command. Once the migration has been created, you may migrate your database using the migrate command:

php artisan queue:table
php artisan migrate

Redis

In order to use the redis queue driver, you should configure a Redis database connection in your config/database.php configuration file.

If your Redis queue connection uses a Redis Cluster, your queue names must contain a key hash tag. This is required in order to ensure all of the Redis keys for a given queue are placed into the same hash slot:

'redis' => [
    'driver' => 'redis',
    'connection' => 'default',
    'queue' => '{default}',
    'retry_after' => 90,
],

Other Driver Prerequisites

The following dependencies are needed for the listed queue drivers:


- Amazon SQS: aws/aws-sdk-php ~3.0
- Beanstalkd: pda/pheanstalk ~3.0
- Redis: predis/predis ~1.0

Creating Jobs

Generating Job Classes

By default, all of the queueable jobs for your application are stored in the app/Jobs directory. If the app/Jobs directory doesn’t exist, it will be created when you run the make:job Artisan command. You may generate a new queued job using the Artisan CLI:

php artisan make:job SendReminderEmail

The generated class will implement the Illuminate\Contracts\Queue\ShouldQueue interface, indicating to Laravel that the job should be pushed onto the queue to run asynchronously.

Class Structure

Job classes are very simple, normally containing only a handle method which is called when the job is processed by the queue. To get started, let’s take a look at an example job class. In this example, we’ll pretend we manage a podcast publishing service and need to process the uploaded podcast files before they are published:

<?php
namespace App\Jobs;
use App\Podcast;
use App\AudioProcessor;
use Illuminate\Bus\Queueable;
use Illuminate\Queue\SerializesModels;
use Illuminate\Queue\InteractsWithQueue;
use Illuminate\Contracts\Queue\ShouldQueue;
class ProcessPodcast implements ShouldQueue
{
    use InteractsWithQueue, Queueable, SerializesModels;
    protected $podcast;
    /**
     * Create a new job instance.
     *
     * @param  Podcast  $podcast
     * @return void
     */
    public function __construct(Podcast $podcast)
    {
        $this->podcast = $podcast;
    }
    /**
     * Execute the job.
     *
     * @param  AudioProcessor  $processor
     * @return void
     */
    public function handle(AudioProcessor $processor)
    {
        // Process uploaded podcast...
    }
}

In this example, note that we were able to pass an Eloquent model directly into the queued job’s constructor. Because of the SerializesModels trait that the job is using, Eloquent models will be gracefully serialized and unserialized when the job is processing. If your queued job accepts an Eloquent model in its constructor, only the identifier for the model will be serialized onto the queue. When the job is actually handled, the queue system will automatically re-retrieve the full model instance from the database. It’s all totally transparent to your application and prevents issues that can arise from serializing full Eloquent model instances.

The handle method is called when the job is processed by the queue. Note that we are able to type-hint dependencies on the handle method of the job. The Laravel service container automatically injects these dependencies.

{note} Binary data, such as raw image contents, should be passed through the base64_encode function before being passed to a queued job. Otherwise, the job may not properly serialize to JSON when being placed on the queue.

Dispatching Jobs

Once you have written your job class, you may dispatch it using the dispatch helper. The only argument you need to pass to the dispatch helper is an instance of the job:

<?php
namespace App\Http\Controllers;
use App\Jobs\ProcessPodcast;
use Illuminate\Http\Request;
use App\Http\Controllers\Controller;
class PodcastController extends Controller
{
    /**
     * Store a new podcast.
     *
     * @param  Request  $request
     * @return Response
     */
    public function store(Request $request)
    {
        // Create podcast...
        dispatch(new ProcessPodcast($podcast));
    }
}

{tip} The dispatch helper provides the convenience of a short, globally available function, while also being extremely easy to test. Check out the Laravel testing documentation to learn more.

Delayed Dispatching

If you would like to delay the execution of a queued job, you may use the delay method on your job instance. The delay method is provided by the Illuminate\Bus\Queueable trait, which is included by default on all generated job classes. For example, let’s specify that a job should not be available for processing until 10 minutes after it has been dispatched:

<?php
namespace App\Http\Controllers;
use Carbon\Carbon;
use App\Jobs\ProcessPodcast;
use Illuminate\Http\Request;
use App\Http\Controllers\Controller;
class PodcastController extends Controller
{
    /**
     * Store a new podcast.
     *
     * @param  Request  $request
     * @return Response
     */
    public function store(Request $request)
    {
        // Create podcast...
        $job = (new ProcessPodcast($podcast))
                    ->delay(Carbon::now()->addMinutes(10));
        dispatch($job);
    }
}

{note} The Amazon SQS queue service has a maximum delay time of 15 minutes.

Customizing The Queue & Connection

Dispatching To A Particular Queue

By pushing jobs to different queues, you may “categorize” your queued jobs and even prioritize how many workers you assign to various queues. Keep in mind, this does not push jobs to different queue “connections” as defined by your queue configuration file, but only to specific queues within a single connection. To specify the queue, use the onQueue method on the job instance:

<?php
namespace App\Http\Controllers;
use App\Jobs\ProcessPodcast;
use Illuminate\Http\Request;
use App\Http\Controllers\Controller;
class PodcastController extends Controller
{
    /**
     * Store a new podcast.
     *
     * @param  Request  $request
     * @return Response
     */
    public function store(Request $request)
    {
        // Create podcast...
        $job = (new ProcessPodcast($podcast))->onQueue('processing');
        dispatch($job);
    }
}

Dispatching To A Particular Connection

If you are working with multiple queue connections, you may specify which connection to push a job to. To specify the connection, use the onConnection method on the job instance:

<?php
namespace App\Http\Controllers;
use App\Jobs\ProcessPodcast;
use Illuminate\Http\Request;
use App\Http\Controllers\Controller;
class PodcastController extends Controller
{
    /**
     * Store a new podcast.
     *
     * @param  Request  $request
     * @return Response
     */
    public function store(Request $request)
    {
        // Create podcast...
        $job = (new ProcessPodcast($podcast))->onConnection('sqs');
        dispatch($job);
    }
}

Of course, you may chain the onConnection and onQueue methods to specify the connection and the queue for a job:

$job = (new ProcessPodcast($podcast))
                ->onConnection('sqs')
                ->onQueue('processing');

Specifying Max Job Attempts / Timeout Values

Max Attempts

One approach to specifying the maximum number of times a job may be attempted is via the --tries switch on the Artisan command line:

php artisan queue:work --tries=3

However, you may take a more granular approach by defining the maximum number of attempts on the job class itself. If the maximum number of attempts is specified on the job, it will take precedence over the value provided on the command line:

<?php
namespace App\Jobs;
class ProcessPodcast implements ShouldQueue
{
    /**
     * The number of times the job may be attempted.
     *
     * @var int
     */
    public $tries = 5;
}

Timeout

Likewise, the maximum number of seconds that jobs can run may be specified using the --timeout switch on the Artisan command line:

php artisan queue:work --timeout=30

However, you may also define the maximum number of seconds a job should be allowed to run on the job class itself. If the timeout is specified on the job, it will take precedence over any timeout specified on the command line:

<?php
namespace App\Jobs;
class ProcessPodcast implements ShouldQueue
{
    /**
     * The number of seconds the job can run before timing out.
     *
     * @var int
     */
    public $timeout = 120;
}

Error Handling

If an exception is thrown while the job is being processed, the job will automatically be released back onto the queue so it may be attempted again. The job will continue to be released until it has been attempted the maximum number of times allowed by your application. The maximum number of attempts is defined by the --tries switch used on the queue:work Artisan command. Alternatively, the maximum number of attempts may be defined on the job class itself. More information on running the queue worker can be found below.

Running The Queue Worker

Laravel includes a queue worker that will process new jobs as they are pushed onto the queue. You may run the worker using the queue:work Artisan command. Note that once the queue:work command has started, it will continue to run until it is manually stopped or you close your terminal:

php artisan queue:work

{tip} To keep the queue:work process running permanently in the background, you should use a process monitor such as Supervisor to ensure that the queue worker does not stop running.

Remember, queue workers are long-lived processes and store the booted application state in memory. As a result, they will not notice changes in your code base after they have been started. So, during your deployment process, be sure to restart your queue workers.

Specifying The Connection & Queue

You may also specify which queue connection the worker should utilize. The connection name passed to the work command should correspond to one of the connections defined in your config/queue.php configuration file:

php artisan queue:work redis

You may customize your queue worker even further by only processing particular queues for a given connection. For example, if all of your emails are processed in an emails queue on your redis queue connection, you may issue the following command to start a worker that only processes only that queue:

php artisan queue:work redis --queue=emails

Resource Considerations

Daemon queue workers do not “reboot” the framework before processing each job. Therefore, you should free any heavy resources after each job completes. For example, if you are doing image manipulation with the GD library, you should free the memory with imagedestroy when you are done.

Queue Priorities

Sometimes you may wish to prioritize how your queues are processed. For example, in your config/queue.php you may set the default queue for your redis connection to low. However, occasionally you may wish to push a job to a high priority queue like so:

dispatch((new Job)->onQueue('high'));

To start a worker that verifies that all of the high queue jobs are processed before continuing to any jobs on the low queue, pass a comma-delimited list of queue names to the work command:

php artisan queue:work --queue=high,low

Queue Workers & Deployment

Since queue workers are long-lived processes, they will not pick up changes to your code without being restarted. So, the simplest way to deploy an application using queue workers is to restart the workers during your deployment process. You may gracefully restart all of the workers by issuing the queue:restart command:

php artisan queue:restart

This command will instruct all queue workers to gracefully “die” after they finish processing their current job so that no existing jobs are lost. Since the queue workers will die when the queue:restart command is executed, you should be running a process manager such as Supervisor to automatically restart the queue workers.

Job Expirations & Timeouts

Job Expiration

In your config/queue.php configuration file, each queue connection defines a retry_after option. This option specifies how many seconds the queue connection should wait before retrying a job that is being processed. For example, if the value of retry_after is set to 90, the job will be released back onto the queue if it has been processing for 90 seconds without being deleted. Typically, you should set the retry_after value to the maximum number of seconds your jobs should reasonably take to complete processing.

{note} The only queue connection which does not contain a retry_after value is Amazon SQS. SQS will retry the job based on the Default Visibility Timeout which is managed within the AWS console.

Worker Timeouts

The queue:work Artisan command exposes a --timeout option. The --timeout option specifies how long the Laravel queue master process will wait before killing off a child queue worker that is processing a job. Sometimes a child queue process can become “frozen” for various reasons, such as an external HTTP call that is not responding. The --timeout option removes frozen processes that have exceeded that specified time limit:

php artisan queue:work --timeout=60

The retry_after configuration option and the --timeout CLI option are different, but work together to ensure that jobs are not lost and that jobs are only successfully processed once.

{note} The --timeout value should always be at least several seconds shorter than your retry_after configuration value. This will ensure that a worker processing a given job is always killed before the job is retried. If your --timeout option is longer than your retry_after configuration value, your jobs may be processed twice.

Worker Sleep Duration

When jobs are available on the queue, the worker will keep processing jobs with no delay in between them. However, the sleep option determines how long the worker will “sleep” if there are no new jobs available. While sleeping, the worker will not process any new jobs - the jobs will be processed after the worker wakes up again.

php artisan queue:work --sleep=3

Supervisor Configuration

Installing Supervisor

Supervisor is a process monitor for the Linux operating system, and will automatically restart your queue:work process if it fails. To install Supervisor on Ubuntu, you may use the following command:

sudo apt-get install supervisor

{tip} If configuring Supervisor yourself sounds overwhelming, consider using Laravel Forge, which will automatically install and configure Supervisor for your Laravel projects.

Configuring Supervisor

Supervisor configuration files are typically stored in the /etc/supervisor/conf.d directory. Within this directory, you may create any number of configuration files that instruct supervisor how your processes should be monitored. For example, let’s create a laravel-worker.conf file that starts and monitors a queue:work process:

[program:laravel-worker]
process_name=%(program_name)s_%(process_num)02d
command=php /home/forge/app.com/artisan queue:work sqs --sleep=3 --tries=3
autostart=true
autorestart=true
user=forge
numprocs=8
redirect_stderr=true
stdout_logfile=/home/forge/app.com/worker.log

In this example, the numprocs directive will instruct Supervisor to run 8 queue:work processes and monitor all of them, automatically restarting them if they fail. Of course, you should change the queue:work sqs portion of the command directive to reflect your desired queue connection.

Starting Supervisor

Once the configuration file has been created, you may update the Supervisor configuration and start the processes using the following commands:

sudo supervisorctl reread
sudo supervisorctl update
sudo supervisorctl start laravel-worker:*

For more information on Supervisor, consult the Supervisor documentation.

Dealing With Failed Jobs

Sometimes your queued jobs will fail. Don’t worry, things don’t always go as planned! Laravel includes a convenient way to specify the maximum number of times a job should be attempted. After a job has exceeded this amount of attempts, it will be inserted into the failed_jobs database table. To create a migration for the failed_jobs table, you may use the queue:failed-table command:

php artisan queue:failed-table
php artisan migrate

Then, when running your queue worker, you should specify the maximum number of times a job should be attempted using the --tries switch on the queue:work command. If you do not specify a value for the --tries option, jobs will be attempted indefinitely:

php artisan queue:work redis --tries=3

Cleaning Up After Failed Jobs

You may define a failed method directly on your job class, allowing you to perform job specific clean-up when a failure occurs. This is the perfect location to send an alert to your users or revert any actions performed by the job. The Exception that caused the job to fail will be passed to the failed method:

<?php
namespace App\Jobs;
use Exception;
use App\Podcast;
use App\AudioProcessor;
use Illuminate\Bus\Queueable;
use Illuminate\Queue\SerializesModels;
use Illuminate\Queue\InteractsWithQueue;
use Illuminate\Contracts\Queue\ShouldQueue;
class ProcessPodcast implements ShouldQueue
{
    use InteractsWithQueue, Queueable, SerializesModels;
    protected $podcast;
    /**
     * Create a new job instance.
     *
     * @param  Podcast  $podcast
     * @return void
     */
    public function __construct(Podcast $podcast)
    {
        $this->podcast = $podcast;
    }
    /**
     * Execute the job.
     *
     * @param  AudioProcessor  $processor
     * @return void
     */
    public function handle(AudioProcessor $processor)
    {
        // Process uploaded podcast...
    }
    /**
     * The job failed to process.
     *
     * @param  Exception  $exception
     * @return void
     */
    public function failed(Exception $exception)
    {
        // Send user notification of failure, etc...
    }
}

Failed Job Events

If you would like to register an event that will be called when a job fails, you may use the Queue::failing method. This event is a great opportunity to notify your team via email or HipChat. For example, we may attach a callback to this event from the AppServiceProvider that is included with Laravel:

<?php
namespace App\Providers;
use Illuminate\Support\Facades\Queue;
use Illuminate\Queue\Events\JobFailed;
use Illuminate\Support\ServiceProvider;
class AppServiceProvider extends ServiceProvider
{
    /**
     * Bootstrap any application services.
     *
     * @return void
     */
    public function boot()
    {
        Queue::failing(function (JobFailed $event) {
            // $event->connectionName
            // $event->job
            // $event->exception
        });
    }
    /**
     * Register the service provider.
     *
     * @return void
     */
    public function register()
    {
        //
    }
}

Retrying Failed Jobs

To view all of your failed jobs that have been inserted into your failed_jobs database table, you may use the queue:failed Artisan command:

php artisan queue:failed

The queue:failed command will list the job ID, connection, queue, and failure time. The job ID may be used to retry the failed job. For instance, to retry a failed job that has an ID of 5, issue the following command:

php artisan queue:retry 5

To retry all of your failed jobs, execute the queue:retry command and pass all as the ID:

php artisan queue:retry all

If you would like to delete a failed job, you may use the queue:forget command:

php artisan queue:forget 5

To delete all of your failed jobs, you may use the queue:flush command:

php artisan queue:flush

Job Events

Using the before and after methods on the Queue facade, you may specify callbacks to be executed before or after a queued job is processed. These callbacks are a great opportunity to perform additional logging or increment statistics for a dashboard. Typically, you should call these methods from a service provider. For example, we may use the AppServiceProvider that is included with Laravel:

<?php
namespace App\Providers;
use Illuminate\Support\Facades\Queue;
use Illuminate\Support\ServiceProvider;
use Illuminate\Queue\Events\JobProcessed;
use Illuminate\Queue\Events\JobProcessing;
class AppServiceProvider extends ServiceProvider
{
    /**
     * Bootstrap any application services.
     *
     * @return void
     */
    public function boot()
    {
        Queue::before(function (JobProcessing $event) {
            // $event->connectionName
            // $event->job
            // $event->job->payload()
        });
        Queue::after(function (JobProcessed $event) {
            // $event->connectionName
            // $event->job
            // $event->job->payload()
        });
    }
    /**
     * Register the service provider.
     *
     * @return void
     */
    public function register()
    {
        //
    }
}

Using the looping method on the Queue facade, you may specify callbacks that execute before the worker attempts to fetch a job from a queue. For example, you might register a Closure to rollback any transactions that were left open by a previously failed job:

Queue::looping(function () {
    while (DB::transactionLevel() > 0) {
        DB::rollBack();
    }
});

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