🐥 Unique jobs when using Laravel Horizon

Unique jobs require a cache driver that supports locks. Currently, the memcached, redis, dynamodb, database, file, and array cache drivers support atomic locks. In addition, unique job constraints do not apply to jobs within batches.

Sometimes, you may want to ensure that only one instance of a specific job is on the queue at any point in time. You may do so by implementing the ShouldBeUnique interface on your job class. This interface does not require you to define any additional methods on your class:

use Illuminate\Contracts\Queue\ShouldQueue;
use Illuminate\Contracts\Queue\ShouldBeUnique;
 
class UpdateSearchIndex implements ShouldQueue, ShouldBeUnique
{
    // ...
}

In the example above, the UpdateSearchIndex job is unique. So, the job will not be dispatched if another instance of the job is already on the queue and has not finished processing.

In certain cases, you may want to define a specific "key" that makes the job unique or you may want to specify a timeout beyond which the job no longer stays unique. To accomplish this, you may define uniqueId and uniqueFor properties or methods on your job class:

use App\Models\Product;
use Illuminate\Contracts\Queue\ShouldQueue;
use Illuminate\Contracts\Queue\ShouldBeUnique;
 
class UpdateSearchIndex implements ShouldQueue, ShouldBeUnique
{
    /**
     * The product instance.
     *
     * @var \App\Product
     */
    public $product;
 
    /**
     * The number of seconds after which the job's unique lock will be released.
     *
     * @var int
     */
    public $uniqueFor = 3600;
 
    /**
     * Get the unique ID for the job.
     */
    public function uniqueId(): string
    {
        return $this->product->id;
    }
}

In the example above, the UpdateSearchIndex job is unique by a product ID. So, any new dispatches of the job with the same product ID will be ignored until the existing job has completed processing. In addition, if the existing job is not processed within one hour, the unique lock will be released and another job with the same unique key can be dispatched to the queue.

If your application dispatches jobs from multiple web servers or containers, you should ensure that all of your servers are communicating with the same central cache server so that Laravel can accurately determine if a job is unique.

source