Yii2 Background Jobs & Queue System

Handling long-running tasks synchronously in Yii2 can slow down your application. Yii2 Queue allows you to process tasks in the background, improving performance and user experience.

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Why Use Yii2 Queue?

• Asynchronous Processing – Avoid blocking user requests.
• Scalability – Handle large volumes of tasks.
• Retry Mechanism – Automatically retry failed jobs.
• Supports Multiple Drivers – Works with MySQL, Redis, RabbitMQ, Beanstalk, etc.

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Installing Yii2 Queue

Yii2 provides an official yii2-queue extension. Install it using Composer:

composer require yiisoft/yii2-queue

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Configuring Queue in Yii2

Yii2 Queue supports multiple backends. Here’s how to set up a MySQL queue (you can replace it with Redis, RabbitMQ, etc.).

1. Database (MySQL) Configuration

Edit your Yii2 configuration file (config/console.php for Basic Template or console/config/main.php for Advanced Template):

'components' => [
    'queue' => [
        'class' => \yii\queue\db\Queue::class,
        'db' => 'db', // Database connection component
        'tableName' => '{{%queue}}', // Table storing the queue
        'channel' => 'default', // Queue channel
        'mutex' => \yii\mutex\MysqlMutex::class, // Avoid race conditions
    ],
],

Run migrations to create the queue table:

php yii queue/db/init
php yii migrate

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2. Creating a Queue Job

Create a job class inside console/jobs/SendEmailJob.php:

namespace console\jobs;
use yii\base\BaseObject;
use yii\queue\JobInterface;
class SendEmailJob extends BaseObject implements JobInterface
{
    public $email;
    
    public function execute($queue)
    {
        \Yii::$app->mailer->compose()
            ->setTo($this->email)
            ->setFrom('admin@example.com')
            ->setSubject('Welcome Email')
            ->setTextBody('Thank you for signing up!')
            ->send();
        
        echo "Email sent to {$this->email}\n";
    }
}

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3. Pushing a Job to the Queue

Add a job in your controller or service:

Yii::$app->queue->push(new \console\jobs\SendEmailJob([
    'email' => 'user@example.com'
]));

This does not execute the job immediately. It stores it in the queue to be processed later.

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Running the Queue

There are two ways to run queue workers:

1. Running the Queue via Cron Job

You can set up a cron job to process the queue every minute by adding this command to crontab:

* * * * * php /path-to-your-project/yii queue/run --verbose=1

This approach works well for low to medium traffic applications.

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2. Running the Queue as a Daemon (Supervisor)

For high-volume queues, it's better to run the worker as a long-running process instead of running it every minute via cron. This can be achieved using Supervisor.

Why Use Supervisor Instead of Cron?

• Faster Execution – Jobs are processed immediately, rather than waiting for the next cron run.
• Continuous Running – Unlike cron, Supervisor keeps listening for new jobs without restarting every minute.
• Prevents Overlapping – If a cron job runs every minute and a job takes longer, multiple cron jobs may run simultaneously, causing conflicts.
• Automatic Restart – If the queue crashes, Supervisor automatically restarts it.

Installing and Configuring Supervisor

1. Install Supervisor:

sudo apt install supervisor

2. Create a new Supervisor config file:

sudo nano /etc/supervisor/conf.d/yii2-queue.conf

3. Add the following configuration:

[program:yii2-queue]
command=php /path-to-your-project/yii queue/listen
autostart=true
autorestart=true
stderr_logfile=/var/log/yii2-queue.err.log
stdout_logfile=/var/log/yii2-queue.out.log

4. Reload Supervisor:

sudo supervisorctl reread
sudo supervisorctl update
sudo supervisorctl start yii2-queue

Now, the queue runs in the background without manual intervention!

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Choosing Between Cron and Supervisor

Feature	Cron Job	Supervisor
Job Execution Speed	Runs jobs every minute	Jobs run instantly
Performance	Can be slow for high-traffic apps	Best for high-volume processing
Reliability	May cause overlapping jobs	Automatically restarts on failures
Best For	Low to medium traffic	High-performance applications

 Conclusion:

• If your app has low to medium traffic, cron jobs are fine.
• If you need real-time processing and high reliability, use Supervisor.

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Handling Failed Jobs

If a job fails, Yii2 can retry it automatically:

Yii::$app->queue->push(new SendEmailJob([
    'email' => 'user@example.com'
]), 5); // Retry 5 times before failing permanently

View failed jobs:

php yii queue/info

Manually retry failed jobs:

php yii queue/retry 10  // Retry job with ID 10

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Best Practices for Yii2 Queues

• Use Supervisor for long-running jobs.
• Retry failed jobs using Yii2 Queue retry mechanism.
• Use Redis/RabbitMQ for high-performance queuing.
• Avoid queueing large payloads (store large data in DB and pass only IDs).
• Log queue failures for debugging.

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Conclusion

Yii2 Queue makes background processing simple. Whether sending emails, processing payments, or running heavy computations, you can improve performance and scalability with background jobs.