Issue #3283162: Automatically retry image generation if image module's lock is held

<?php

declare(strict_types=1);

namespace Drupal\stage_file_proxy\Controller;

use Drupal\Core\DependencyInjection\ContainerInjectionInterface;

use Drupal\Core\File\FileSystemInterface;

use Drupal\Core\Image\ImageFactory;

use Drupal\Core\Lock\LockBackendInterface;

use Drupal\Core\StreamWrapper\StreamWrapperManagerInterface;

use Drupal\image\Controller\ImageStyleDownloadController as CoreImageStyleDownloadController;

use Drupal\image\ImageStyleInterface;

use Symfony\Component\DependencyInjection\ContainerInterface;

use Symfony\Component\HttpFoundation\Request;

use Symfony\Component\HttpKernel\Exception\ServiceUnavailableHttpException;

/**

 * Decorate core's image style controller to retry failed requests.

 */

final class ImageStyleDownloadController implements ContainerInjectionInterface {

  private CoreImageStyleDownloadController $decorated;

  /**

   * Constructs an ImageStyleDownloadController object.

   *

   * @param \Drupal\Core\Lock\LockBackendInterface $lock

   *   The lock backend.

   * @param \Drupal\Core\Image\ImageFactory $image_factory

   *   The image factory.

   * @param \Drupal\Core\StreamWrapper\StreamWrapperManagerInterface $stream_wrapper_manager

   *   The stream wrapper manager.

   * @param \Drupal\Core\File\FileSystemInterface $file_system

   *   The system service.

   */

  public function __construct(LockBackendInterface $lock, ImageFactory $image_factory, StreamWrapperManagerInterface $stream_wrapper_manager, FileSystemInterface $file_system = NULL) {

    $this->decorated = new CoreImageStyleDownloadController($lock, $image_factory, $stream_wrapper_manager, $file_system);

  }

  /**

   * {@inheritdoc}

   */

  public static function create(ContainerInterface $container) {

    return new static(

      $container->get('lock'),

      $container->get('image.factory'),

      $container->get('stream_wrapper_manager'),

      $container->get('file_system')

    );

  }

  /**

   * Retry generating a derivative in the case of parallel requests.

   *

   * Stage File Proxy is often used on locals that may have slower internet

   * connections compared to hosted environments. If multiple image style

   * requests need to download a large image, image module will immediately

   * return a 503 on subsequent requests while the first request is downloading

   * the source image. This can also happen in "normal" hosting environments if

   * enough parallel requests happen and a caching reverse proxy or CDN isn't in

   * place to combine multiple requests into a single Drupal request.

   *

   * To work around this, we decorate core's image controller and try to deliver

   * the image again for up to 5 seconds. While this could cause a queue of PHP

   * processes in production workloads, we assume that Stage File Proxy is used

   * in scenarios where that won't be an issue.

   *

   * @param \Symfony\Component\HttpFoundation\Request $request

   *   The request object.

   * @param string $scheme

   *   The file scheme, defaults to 'private'.

   * @param \Drupal\image\ImageStyleInterface $image_style

   *   The image style to deliver.

   *

   * @return \Symfony\Component\HttpFoundation\BinaryFileResponse|\Symfony\Component\HttpFoundation\Response

   *   The transferred file as response or some error response.

   *

   * @throws \Symfony\Component\HttpKernel\Exception\NotFoundHttpException

   *   Thrown when the file request is invalid.

   * @throws \Symfony\Component\HttpKernel\Exception\AccessDeniedHttpException

   *   Thrown when the user does not have access to the file.

   * @throws \Symfony\Component\HttpKernel\Exception\ServiceUnavailableHttpException

   *   Thrown when the file is still being generated.

   */

  public function deliver(Request $request, string $scheme, ImageStyleInterface $image_style) {

    $tries = 5;

    do {

      try {

        return $this->decorated->deliver($request, $scheme, $image_style);

      }

      catch (ServiceUnavailableHttpException $e) {

        $tries--;

        usleep(250000);

      }

    } while ($tries > 0);

    throw $e;

  }

}

<?php

declare(strict_types=1);

namespace Drupal\stage_file_proxy\EventSubscriber;

use Drupal\Core\Routing\RouteBuildEvent;

use Drupal\Core\Routing\RoutingEvents;

use Drupal\stage_file_proxy\Controller\ImageStyleDownloadController;

use Symfony\Component\EventDispatcher\EventSubscriberInterface;

/**

 * Decorates core's image download controller with our own.

 */

class ImageDownloadControllerSubscriber implements EventSubscriberInterface {

  /**

   * Overwrite the _controller key to point to our controller.

   *

   * @param \Drupal\Core\Routing\RouteBuildEvent $event

   *   The event containing the route being built.

   *

   * @return void

   */

  public function onAlterDecorateController(RouteBuildEvent $event): void {

    $to_alter = [

      'image.style_public',

      'image.style_private',

    ];

    foreach ($to_alter as $name) {

      $definition = $event->getRouteCollection()->get($name);

      if ($definition) {

        $definition->setDefault('_controller', ImageStyleDownloadController::class . "::deliver");

      }

    }

  }

  /**

   * {@inheritdoc}

   */

  public static function getSubscribedEvents(): array {

    $events[RoutingEvents::ALTER] = 'onAlterDecorateController';

    return $events;

  }

}

  logger.channel.stage_file_proxy:

    parent: logger.channel_base

    arguments: ['stage_file_proxy']

  stage_file_proxy.image_download_controller:

    class: Drupal\stage_file_proxy\EventSubscriber\ImageDownloadControllerSubscriber

    tags:

      - { name: event_subscriber }