o11y-8.x-1.x-dev/modules/o11y_metrics/src/EventSubscriber/RemoveMetricsOnBucketsChange.php

<?php

namespace Drupal\o11y_metrics\EventSubscriber;

use Symfony\Component\EventDispatcher\EventSubscriberInterface;
use Drupal\o11y_metrics\Bridge\PrometheusBridgeInterface;
use Drupal\Core\Config\ConfigEvents;
use Drupal\Core\Config\ConfigCrudEvent;
use Drupal\Core\Config\ConfigFactoryInterface;
use Drupal\Core\Config\StorageTransformEvent;

/**
 * Reacts on config save.
 *
 * This event subscriber reacts on config save, and if the buckets have
 * changed, it cleans the data of the collector class.
 * Site wise, wipe_client_storage_on_drush_config_import can be set to 0 but if
 * we are importing a config that changes buckets then we have to make sure
 * that the local storage is cleaned otherwise the new buckets do not get
 * regitered by the library.
 */
class RemoveMetricsOnBucketsChange implements EventSubscriberInterface {

  /**
   * The promphp bridge.
   *
   * @var \Drupal\o11y_metrics\Bridge\PrometheusBridgeInterface
   */
  protected $promBridge;

  /**
   * The metrics source class name.
   *
   * @var string
   */
  protected $metricsSourceClassName;

  /**
   * Buckets detected before config import.
   *
   * @var array
   */
  protected $bucketsBeforeOnConfigImport;

  /**
   * Constructor.
   */
  public function __construct(
    PrometheusBridgeInterface $promBridge,
    ConfigFactoryInterface $config,
    string $metricsSourceClassName
  ) {
    $this->promBridge = $promBridge;
    $this->metricsSourceClassName = $metricsSourceClassName;
    $this->bucketsBeforeOnConfigImport = $config->get($metricsSourceClassName::CONFIG_NAME)->getOriginal('buckets');
  }

  /**
   * Callback for ConfigEvents::SAVE event.
   *
   * Called during both config import and config form submit.
   * Removes metrics if a specific configuration has changed.
   *
   * @param \Drupal\Core\Config\ConfigCrudEvent $event
   *   The Event to process.
   */
  public function removeMetricsOfSourceIfBucketsHaveChanged(ConfigCrudEvent $event) {
    $config = $event->getConfig();
    if ($config->getName() !== $this->metricsSourceClassName::CONFIG_NAME) {
      return;
    }
    // During config import getOriginal returns NULL, so we use the field.
    // We still need to give priority to getOriginal because during config form
    // submit the actual original data is found on the config object obtained
    // from the $event (this callback param) and not from the config.factory
    // (from the constructor) which contains the already changed value.
    $bucketsBefore = $config->getOriginal('buckets') ?? $this->bucketsBeforeOnConfigImport;
    $bucketsNow = $config->get('buckets');
    if ($bucketsBefore != $bucketsNow) {
      $this->promBridge->removeMetricsOfSource($this->metricsSourceClassName);
    }
  }

  /**
   * Callback for STORAGE_TRANSFORM_IMPORT event.
   *
   * Not called when the config changes by submitting the config form.
   * Called only during config import.
   * This handler, while empty, needs to exist in order to have drupal
   * instanciate this service early in the config import process and have the
   * right value assigned to $this->bucketsBeforeOnConfigImport in the
   * constructor.
   *
   * @SuppressWarnings(PHPMD.UnusedFormalParameter)
   */
  public function onStorageTransforImport(StorageTransformEvent $e) {
  }

  /**
   * {@inheritdoc}
   */
  public static function getSubscribedEvents() {
    $events[ConfigEvents::SAVE][] = ['removeMetricsOfSourceIfBucketsHaveChanged'];
    $events[ConfigEvents::STORAGE_TRANSFORM_IMPORT][] = ['onStorageTransforImport'];
    return $events;
  }

}