Add ping in queue processor

We did most of this in a custom module except for the ClientFactory.php

  $http_client_config = Settings::get('http_client_config', []);
    if (isset($http_client_config['proxy'])) {
      $http_options['proxy'] = $http_client_config['proxy'];
   }

We patched this to be able to have a custom proxy specific for mailchimp without having to make it sitewide.

In a custom module, we did something like this :

// mymodule.module

function mymodule_module_implements_alter(array &$implementations, $hook) {
  if ($hook === 'cron' && isset($implementations['mailchimp'])) {
    unset($implementations['mailchimp']);
  }
}

function mymodule_cron() {
  $config = \Drupal::config('mailchimp.settings');
  if (!$config->get('cron')) {
    return;
  }
  \Drupal::service('mymodule.queue_processor')
    ->process((int) ($config->get('cron_limit') ?: 50));
}

I've tried to retrieve the specific code for this from our custom module and make it generic

// src/Queue/Processor.php

namespace Drupal\mymodule\Queue;

use Drupal\Core\Config\ConfigFactoryInterface;
use Drupal\Core\Queue\QueueFactory;
use Drupal\Core\State\StateInterface;
use Drupal\mailchimp\Queue\Processor as ContribProcessor;
use GuzzleHttp\ClientInterface;
use GuzzleHttp\Exception\TransferException;

class Processor extends ContribProcessor {

  public function __construct(
    ConfigFactoryInterface $config_factory,
    QueueFactory $queue_factory,
    protected ClientInterface $httpClient,
    protected StateInterface $state,
  ) {
    parent::__construct($config_factory, $queue_factory);
  }

  public function process(?int $batch_limit = NULL) {
    if (!$this->ping()) {
      \Drupal::logger('mymodule')->warning(
        'Mailchimp /ping failed. Queue processing skipped to prevent data loss.'
      );
      return 0;
    }
    return parent::process($batch_limit);
  }

  /**
   * Checks Mailchimp reachability via /ping. Result cached in State for 60s.
   */
  protected function ping(): bool {
    $now = \Drupal::time()->getRequestTime();

    if ($now - (int) $this->state->get('mymodule.ping_time', 0) < 60) {
      return (bool) $this->state->get('mymodule.ping_ok', TRUE);
    }

    $api_key  = (string) $this->configFactory->get('mailchimp.settings')->get('api_key');
    $dash_pos = strrpos($api_key, '-');
    if (!$api_key || $dash_pos === FALSE) {
      return FALSE;
    }

    try {
      $response = $this->httpClient->request('GET',
        sprintf('https://%s.api.mailchimp.com/3.0/ping', substr($api_key, $dash_pos + 1)),
        ['auth' => ['anystring', $api_key], 'timeout' => 10]
      );
      $ok = $response->getStatusCode() === 200;
    }
    catch (TransferException $e) {
      $ok = FALSE;
    }

    $this->state->set('mymodule.ping_time', $now);
    $this->state->set('mymodule.ping_ok', $ok);
    return $ok;
  }

}

# mymodule.services.yml
services:
  mymodule.queue_processor:
    class: Drupal\mymodule\Queue\Processor
    arguments: ['@config.factory', '@queue', '@http_client', '@state']

This pattern would be a clean addition directly to the contrib Processor:

• A ping_before_process boolean in mailchimp.settings (opt-in, default false for backward compatibility)
• A ping_cache_ttl integer setting (default 60 seconds)
• The /ping check at the top of Processor::process(), skipping queue processing if unreachable