Add logging for unexpected states when we reach the end of sending

[MAILPOET-5881]

mailpoet/lib/Cron/Workers/SendingQueue/SendingQueue.php

@@ -645,6 +645,20 @@ class SendingQueue {
   }
 
   private function endSending(ScheduledTaskEntity $task, NewsletterEntity $newsletter): void {
+    // We should handle all transitions into these states in the processSending method and end processing there or we throw an exception
+    // This might theoretically happen when multiple cron workers are running in parallel which we don't support and try to prevent
+    $unexpectedStates = [
+      ScheduledTaskEntity::STATUS_PAUSED,
+      ScheduledTaskEntity::STATUS_INVALID,
+      ScheduledTaskEntity::STATUS_SCHEDULED,
+    ];
+    if (in_array($task->getStatus(), $unexpectedStates)) {
+      $this->loggerFactory->getLogger(LoggerFactory::TOPIC_NEWSLETTERS)->error(
+        'Sending task reached end of processing in sending queue worker in an unexpected state.',
+        ['task_id' => $task->getId(), 'status' => $task->getStatus()]
+      );
+      return;
+    }
     // The task is running but there is no one to send to.
     // This may happen when we send to all but the execution is interrupted (e.g. by PHP time limit) and we don't update the task status
     // or if we trigger sending to a newsletter without any subscriber (e.g. scheduled for long time but all were deleted)

mailpoet/tests/integration/Cron/Workers/SendingQueue/SendingQueueTest.php

@@ -16,6 +16,7 @@ use MailPoet\Cron\Workers\SendingQueue\Tasks\Mailer as MailerTask;
 use MailPoet\Cron\Workers\SendingQueue\Tasks\Newsletter as NewsletterTask;
 use MailPoet\Cron\Workers\StatsNotifications\Scheduler as StatsNotificationsScheduler;
 use MailPoet\DI\ContainerWrapper;
+use MailPoet\Entities\LogEntity;
 use MailPoet\Entities\NewsletterEntity;
 use MailPoet\Entities\NewsletterLinkEntity;
 use MailPoet\Entities\NewsletterSegmentEntity;
@@ -54,6 +55,7 @@ use MailPoet\Test\DataFactories\Subscriber as SubscriberFactory;
 use MailPoet\Util\Security;
 use MailPoet\WP\Functions as WPFunctions;
 use MailPoetVendor\Carbon\Carbon;
+use MailPoetVendor\Monolog\Logger;
 
 class SendingQueueTest extends \MailPoetTest {
   /** @var SendingQueueWorker */
@@ -1459,6 +1461,36 @@ class SendingQueueTest extends \MailPoetTest {
     verify($newsletter->getStatus())->equals(NewsletterEntity::STATUS_SENDING);
   }
 
+  public function testItLogsWhenSendingReachesEndAndTaskHasAnUnexpectedState() {
+    // No subscribers in queue to skip batch processing
+    $this->scheduledTaskSubscribersRepository->setSubscribers(
+      $this->scheduledTask,
+      []
+    );
+
+    // To emulate unexpected task status change we switch task status to paused in mailer task mock
+    $task = $this->scheduledTask;
+    $em = $this->entityManager;
+    $mailerTaskMock = $this->createMock(MailerTask::class);
+    $mailerTaskMock
+      ->expects($this->once())
+      ->method('configureMailer')
+      ->willReturnCallback(function() use ($task, $em) {
+        $task->setStatus(ScheduledTaskEntity::STATUS_PAUSED);
+        $em->flush();
+      });
+
+    $sendingQueueWorker = $this->getSendingQueueWorker($mailerTaskMock);
+    $sendingQueueWorker->process();
+
+    $logs = $this->entityManager->getRepository(LogEntity::class)->findAll();
+    $log = $logs[0] ?? null;
+    $this->assertInstanceOf(LogEntity::class, $log);
+    verify($log->getLevel())->equals(Logger::ERROR);
+    verify($log->getMessage())->stringContainsString('Sending task reached end of processing in sending queue worker in an unexpected state.');
+    verify($log->getMessage())->stringContainsString('"task_id":' . $task->getId());
+  }
+
   public function testProcessMarksScheduledTaskInProgressAsFalseWhenProperlyProcessingTask() {
     $sendingQueueWorker = $this->getSendingQueueWorker();
     $sendingQueueWorker->process();
@@ -1600,7 +1632,7 @@ class SendingQueueTest extends \MailPoetTest {
       $this->sendingQueuesRepository,
       $this->entityManager,
       $this->statisticsNewslettersRepository,
-      $authorizedEmailControllerMock ?? $this->authorizedEmailsController
+      $authorizedEmailControllerMock ?? $this->authorizedEmailsController,
     );
   }