Queue Promises

The module allows chaining of Laravel jobs. The promise will be executed after all chained jobs are finished (either completed successfully or failed). The promise has access to job results.

Installation

• Install the package with composer:

composer require tochka-developers/queue-promises

• (Laravel 5.4) Register a ServiceProvider in config/app.php

'providers' => [
    ...
    \Tochka\Queue\Promises\QueuePromisesServiceProvider::class
    ...
]

• Publish the configuration:

php artisan vendor:publish --provider="Tochka\Queue\Promises\QueuePromisesServiceProvider"

• Configure the promise storage in config/promises.php.

• Create the promise storage tables:

php artisan migrate

Usage

Creating a Promise

All promises are derived from Tochka\Queue\Promises\Jobs\Promise. You can create a template promise with artisan:

php artisan make:promise TestPromise

Class details

The promise class is rather straightforward, as only two methods are needed: success and errors. The success is called by the provider if all chained jobs have completed successfully. The errors is called if any of the jobs failed.

<?php

namespace App\Promises;

use Tochka\Queue\Promises\Jobs\Promise;

class TestPromise extends Promise
{
    /**
     * Instance initialization
     *
     * @return void
     */
    public function __construct()
    {
        // Jobs chaining may be done here
    }
    
    /**
     * This will be called after all jobs of the promise have finished execution, but before success or errors.
     * If this method returns false, success and errors won't be called. 
     *
     * @return bool
     */
    public function before(): bool
    {
        // ...
        return true;
    }

    /**
     * This will be called if all the jobs have completed successfully.
     *
     * @return bool
     */
    public function success(): bool
    {
        // ...
        return true;
    }

    /**
     * This will be called if one or more jobs have failed.
     *
     * @return bool
     */
    public function errors(): bool
    {
        // ...
        return true;
    }
    
    /**
     * This will be called if the promise timed out.
     *
     * @return bool
     */
    public function timeout(): bool
    {
        // ...
        return true;
    }
    
    /**
     * This will be called after the execution of success or errors
     *
     * @return bool
     */
    public function after()
    {
        // ...
        return true;
    }
}

Any of the methods shown above may not be implemented. If a methods is missing it is assumed to do nothing and return true.

Chain Initialization

In order for jobs to attach to a promise they must implement the Tochka\Queue\Promises\Contracts\MayPromised interface. The most common use cases are collected in the Tochka\Queue\Promises\Jobs\Promised trait. You may simply attach these to your class like this:

<?php

namespace App\Jobs;

use Illuminate\Bus\Queueable;
use Illuminate\Contracts\Queue\ShouldQueue;
use Illuminate\Foundation\Bus\Dispatchable;
use Illuminate\Queue\InteractsWithQueue;
use Illuminate\Queue\SerializesModels;
use Tochka\Queue\Promises\Contracts\MayPromised;
use Tochka\Queue\Promises\Jobs\Promised;

class SomeJob implements ShouldQueue, MayPromised
{
    use Dispatchable, InteractsWithQueue, Queueable, SerializesModels, Promised;

    public $text;

    public function __construct($text)
    {
        $this->text = $text;
    }

    public function handle()
    {
        // some actions
    }
}

The chain is constructed by adding any number of jobs to the promise:

$promise = new TestPromise();

$promise->add(new SomeJob('job 1'))
    ->add(new SomeJob('job 2'))
    ->add(new SomeJob('job 3'))
    ->add(new SomeJob('job 4'));

After that the promise can be run in one of two modes:

$promise->runSync();    // Run the promise synchronously 
$promise->runAsync();   // Run the promise asynchronously

• In synchronous mode all chained jobs will be run sequentially, one at a time, until either one of them fails or all complete successfully. After that, the success or errors of the promise will be executed.
• In asynchronous mode all jobs will be queued immediately, and the promise will wait for them to finish.

The termination conditions can be finely configured via method call:

$promise->setPromiseFinishConditions(
    true, // The promise must execute when a job completes successfully for the first time.  
    true  // The promise must execute when a job fails for the first time.
);

For convenience, runSync and runAsync may also take the same parameters.

Waiting For Events

Sometimes it is necessary to execute a promise not just after a number of jobs completed, but also when an event is dispatched. Waiting for the events is done with a Tochka\Queue\Promises\Jobs\WaitEvent job:

$promise = new TestPromise();

$promise->add(new WaitEvent(SomeEvent1::class, 100))
        ->add(new WaitEvent(SomeEvent2::class, 100));
    
$promise->run()

The constructor of a WaitEvent takes a class of the event to wait for and an unique identifier (of unspecified type). If the identifier is not provided, the WaitEvent will wait for any event of the expected class. If the identifier is given to the constructor, the WaitEvent will complete only when the event with this identifier is dispatched. In order for this to work, the event must implement the Tochka\Queue\Promises\Contracts\PromisedEvent interface:

class SomeEvent implements PromisedEvent
{
    public $id;
    public $data;

    public function __construct($id, string $data)
    {
        $this->id = $id;
        $this->data = $data;
    }

    /**
     * Get the event id
     * @return string
     */
    public function getUniqueId()
    {
        return $this->id;
    }
}

getUniqueId must return either an identifier or null if no identifier exists.

Note that WaitEvent will never complete if it waits for a class that does not implement the interface.

Promise Timeout

It may be useful at times to execute the promise after a timeout event if some of chained jobs haven't yet finished. This is achieved with a special delayed checker job.

You have to configure the timeout subsystem:

• set the configuration parameter timeout_queue to contain the name of the queue where the checker jobs will be posted. By default the checker jobs are posted to the default queue.
• run a listener for the timeout queue or add it to a list of queues for existing listener.

After that the promises may be set to expire. Two ways of setting a timeout are possible:

• setTimeout($timeout) — the promise will be executed in the given time (in seconds) or after all jobs have completed (whatever happens first).
• setExpiredAt(Carbon $expired_at) — the promise will be executed at the given timestamp (more or less accurately) or after all jobs have completed (whatever happens first).

If the promise times out, the timeout method is called (if defined).

Processing The Results

The getResults method returns the results of all chained jobs:

public function before(): bool
{
    $results = $this->getResults();
    foreach ($results as $result) {
        $status = $result->getJobStatus(); // This returns the job execution status
    }
}

Job results are returned as classes implementing Tochka\Queue\Promises\Contracts\MayPromised.

Dependency Injection

An alternative way to get the job results is dependency injection versions of generic methods before, success, errors, timeout, and after:

public function errors(SomeJob1 $job1, SomeJob2 $job2): bool
{
    echo $job1->getJobStatus();
    echo $job2->getJobStatus();
}

The DI works like follows:

• if a parameter has a type implementing Tochka\Queue\Promises\Contracts\MayPromised, the corresponding result will be injected into this parameter;
• if a parameter has a type implementing Tochka\Queue\Promises\Contracts\PromisedEvent (which is useful when the promise waits for an event), the event itself will be passed as this parameter;
• if there are more than one result of the required class, only the first one will bind;
• if there are more than one parameter of the same class (for example, if the promise waits for several jobs of the same class), the order of results corresponds to the order of the jobs in the chain:

$promise->add(new SomeJob('job 1'))
        ->add(new SomeJob('job 2'))
        ->add(new SomeJob('job 3'))
        ->add(new SomeJob('job 4'));
    
//...

public function errors(SomeJob $job1, SomeJob $job2, SomeJob $job3, SomeJob $job4): bool
{
    echo $job1->text; // job 1
    echo $job2->text; // job 2
    echo $job3->text; // job 3
    echo $job4->text; // job 4
}

Note that if the promise is run asynchronously, the order of job execution cannot be guaranteed. This may have undesired consequences:

public function errors(SomeJob $job1, SomeJob $job2, SomeJob $job3, SomeJob $job4): bool
{
    echo $job1->text; // job 3
    echo $job2->text; // job 1
    echo $job3->text; // job 2
    echo $job4->text; // job 4
}

• if there is no appropriate result for a parameter, null is passed;
• if a parameter type does not implement Tochka\Queue\Promises\Contracts\MayPromised, then the value passed to it will be constructed with Laravel DI (like the result of calling app() with the class name).

Tochka\Queue\Promises\Contracts\MayPromised interface declares the following methods:

/**
 * Get the job execution status 
 * Returns either MayPromised::JOB_STATUS_SUCCESS or MayPromised::JOB_STATUS_ERROR
 * @return string
 */
public function getJobStatus(): string;

/**
 * Get the job execution errors
 * Returns an array ['code' => ..., 'message' => ...]
 * @return array
 */
public function getJobErrors(): array;