feature #30757 [Messenger] Adding MessageCountAwareInterface to get t…

…ransport message count (weaverryan)

This PR was squashed before being merged into the 4.3-dev branch (closes #30757).

Discussion
----------

[Messenger] Adding MessageCountAwareInterface to get transport message count

| Q             | A
| ------------- | ---
| Branch?       | master
| Bug fix?      | no
| New feature?  | yes
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | none
| License       | MIT
| Doc PR        | symfony/symfony-docs#11236

This adds a new optional interface that receivers should implement to give an approximate number of the messages "waiting" to be handled. Why? Because, with this, you could design a system that dynamically adds/removes worker processes if a specific transport is getting slammed and needs help. Creating that system could be something we discuss for core later, but this at least makes it possible - and means it could be implemented by the user or in a bundle... which I might do if we don't get it in core ;).

Commits
-------

fc5b0cf [Messenger] Adding MessageCountAwareInterface to get transport message count

src/Symfony/Component/Messenger/CHANGELOG.md

@@ -4,6 +4,8 @@ CHANGELOG
 4.3.0
 -----
 
+ * Added optional `MessageCountAwareInterface` that receivers can implement
+   to give information about how many messages are waiting to be processed.
  * [BC BREAK] The `Envelope::__construct()` signature changed:
    you can no longer pass an unlimited number of stamps as the second,
    third, fourth, arguments etc: stamps are now an array passed to the

src/Symfony/Component/Messenger/Tests/Transport/AmqpExt/AmqpExtIntegrationTest.php

@@ -167,6 +167,24 @@ public function testItReceivesSignals()
             , $process->getOutput());
     }
 
+    public function testItCountsMessagesInQueue()
+    {
+        $serializer = $this->createSerializer();
+
+        $connection = Connection::fromDsn(getenv('MESSENGER_AMQP_DSN'));
+        $connection->setup();
+        $connection->queue()->purge();
+
+        $sender = new AmqpSender($connection, $serializer);
+
+        $sender->send($first = new Envelope(new DummyMessage('First')));
+        $sender->send($second = new Envelope(new DummyMessage('Second')));
+        $sender->send($second = new Envelope(new DummyMessage('Third')));
+
+        sleep(1); // give amqp a moment to have the messages ready
+        $this->assertSame(3, $connection->countMessagesInQueue());
+    }
+
     private function waitForOutput(Process $process, string $output, $timeoutInSeconds = 10)
     {
         $timedOutTime = time() + $timeoutInSeconds;

src/Symfony/Component/Messenger/Tests/Transport/Doctrine/ConnectionTest.php

@@ -37,6 +37,9 @@ public function testGetAMessageWillChangeItsStatus()
         $queryBuilder
             ->method('getSQL')
             ->willReturn('');
+        $queryBuilder
+            ->method('getParameters')
+            ->willReturn([]);
         $driverConnection
             ->method('prepare')
             ->willReturn($stmt);
@@ -54,6 +57,9 @@ public function testGetWithNoPendingMessageWillReturnNull()
         $driverConnection = $this->getDBALConnectionMock();
         $stmt = $this->getStatementMock(false);
 
+        $queryBuilder
+            ->method('getParameters')
+            ->willReturn([]);
         $driverConnection->expects($this->once())
             ->method('createQueryBuilder')
             ->willReturn($queryBuilder);
@@ -119,6 +125,7 @@ private function getQueryBuilderMock()
         $queryBuilder->method('orderBy')->willReturn($queryBuilder);
         $queryBuilder->method('setMaxResults')->willReturn($queryBuilder);
         $queryBuilder->method('setParameter')->willReturn($queryBuilder);
+        $queryBuilder->method('setParameters')->willReturn($queryBuilder);
 
         return $queryBuilder;
     }

src/Symfony/Component/Messenger/Tests/Transport/Doctrine/DoctrineIntegrationTest.php

@@ -100,6 +100,46 @@ public function testItRetrieveTheFirstAvailableMessage()
         $this->assertEquals('{"message": "Hi available"}', $encoded['body']);
     }
 
+    public function testItCountMessages()
+    {
+        // insert messages
+        // one currently handled
+        $this->driverConnection->insert('messenger_messages', [
+            'body' => '{"message": "Hi handled"}',
+            'headers' => json_encode(['type' => DummyMessage::class]),
+            'queue_name' => 'default',
+            'created_at' => Connection::formatDateTime(new \DateTime('2019-03-15 12:00:00')),
+            'available_at' => Connection::formatDateTime(new \DateTime('2019-03-15 12:00:00')),
+            'delivered_at' => Connection::formatDateTime(\DateTime::createFromFormat('U.u', microtime(true))),
+        ]);
+        // one available later
+        $this->driverConnection->insert('messenger_messages', [
+            'body' => '{"message": "Hi delayed"}',
+            'headers' => json_encode(['type' => DummyMessage::class]),
+            'queue_name' => 'default',
+            'created_at' => Connection::formatDateTime(new \DateTime('2019-03-15 12:00:00')),
+            'available_at' => Connection::formatDateTime((new \DateTime())->modify('+1 minute')),
+        ]);
+        // one available
+        $this->driverConnection->insert('messenger_messages', [
+            'body' => '{"message": "Hi available"}',
+            'headers' => json_encode(['type' => DummyMessage::class]),
+            'queue_name' => 'default',
+            'created_at' => Connection::formatDateTime(new \DateTime('2019-03-15 12:00:00')),
+            'available_at' => Connection::formatDateTime(new \DateTime('2019-03-15 12:30:00')),
+        ]);
+        // another available
+        $this->driverConnection->insert('messenger_messages', [
+            'body' => '{"message": "Hi available"}',
+            'headers' => json_encode(['type' => DummyMessage::class]),
+            'queue_name' => 'default',
+            'created_at' => Connection::formatDateTime(new \DateTime('2019-03-15 12:00:00')),
+            'available_at' => Connection::formatDateTime(new \DateTime('2019-03-15 12:30:00')),
+        ]);
+
+        $this->assertSame(2, $this->connection->getMessageCount());
+    }
+
     public function testItRetrieveTheMessageThatIsOlderThanRedeliverTimeout()
     {
         $twoHoursAgo = new \DateTime('now');

src/Symfony/Component/Messenger/Transport/AmqpExt/AmqpReceiver.php

@@ -15,6 +15,7 @@
 use Symfony\Component\Messenger\Exception\LogicException;
 use Symfony\Component\Messenger\Exception\MessageDecodingFailedException;
 use Symfony\Component\Messenger\Exception\TransportException;
+use Symfony\Component\Messenger\Transport\Receiver\MessageCountAwareInterface;
 use Symfony\Component\Messenger\Transport\Receiver\ReceiverInterface;
 use Symfony\Component\Messenger\Transport\Serialization\PhpSerializer;
 use Symfony\Component\Messenger\Transport\Serialization\SerializerInterface;
@@ -26,7 +27,7 @@
  *
  * @experimental in 4.2
  */
-class AmqpReceiver implements ReceiverInterface
+class AmqpReceiver implements ReceiverInterface, MessageCountAwareInterface
 {
     private $serializer;
     private $connection;
@@ -87,6 +88,14 @@ public function reject(Envelope $envelope): void
         $this->rejectAmqpEnvelope($this->findAmqpEnvelope($envelope));
     }
 
+    /**
+     * {@inheritdoc}
+     */
+    public function getMessageCount(): int
+    {
+        return $this->connection->countMessagesInQueue();
+    }
+
     private function rejectAmqpEnvelope(\AMQPEnvelope $amqpEnvelope): void
     {
         try {

src/Symfony/Component/Messenger/Transport/AmqpExt/AmqpTransport.php

@@ -12,6 +12,7 @@
 namespace Symfony\Component\Messenger\Transport\AmqpExt;
 
 use Symfony\Component\Messenger\Envelope;
+use Symfony\Component\Messenger\Transport\Receiver\MessageCountAwareInterface;
 use Symfony\Component\Messenger\Transport\Serialization\PhpSerializer;
 use Symfony\Component\Messenger\Transport\Serialization\SerializerInterface;
 use Symfony\Component\Messenger\Transport\SetupableTransportInterface;
@@ -22,7 +23,7 @@
  *
  * @experimental in 4.2
  */
-class AmqpTransport implements TransportInterface, SetupableTransportInterface
+class AmqpTransport implements TransportInterface, SetupableTransportInterface, MessageCountAwareInterface
 {
     private $serializer;
     private $connection;
@@ -75,6 +76,14 @@ public function setup(): void
         $this->connection->setup();
     }
 
+    /**
+     * {@inheritdoc}
+     */
+    public function getMessageCount(): int
+    {
+        return ($this->receiver ?? $this->getReceiver())->getMessageCount();
+    }
+
     private function getReceiver()
     {
         return $this->receiver = new AmqpReceiver($this->connection, $this->serializer);

src/Symfony/Component/Messenger/Transport/AmqpExt/Connection.php

@@ -184,6 +184,14 @@ public function publish(string $body, array $headers = [], int $delay = 0): void
         $this->exchange()->publish($body, $this->queueConfiguration['routing_key'] ?? null, $flags, $attributes);
     }
 
+    /**
+     * Returns an approximate count of the messages in a queue.
+     */
+    public function countMessagesInQueue(): int
+    {
+        return $this->queue()->declareQueue();
+    }
+
     /**
      * @throws \AMQPException
      */

src/Symfony/Component/Messenger/Transport/Doctrine/Connection.php

@@ -14,6 +14,7 @@
 use Doctrine\DBAL\Connection as DBALConnection;
 use Doctrine\DBAL\DBALException;
 use Doctrine\DBAL\Exception\TableNotFoundException;
+use Doctrine\DBAL\Query\QueryBuilder;
 use Doctrine\DBAL\Schema\Schema;
 use Doctrine\DBAL\Schema\Synchronizer\SingleDatabaseSynchronizer;
 use Doctrine\DBAL\Types\Type;
@@ -128,25 +129,14 @@ public function get(): ?array
     {
         $this->driverConnection->beginTransaction();
         try {
-            $query = $this->driverConnection->createQueryBuilder()
-                ->select('m.*')
-                ->from($this->configuration['table_name'], 'm')
-                ->where('m.delivered_at is null OR m.delivered_at < :redeliver_limit')
-                ->andWhere('m.available_at <= :now')
-                ->andWhere('m.queue_name = :queue_name')
+            $query = $this->createAvailableMessagesQueryBuilder()
                 ->orderBy('available_at', 'ASC')
                 ->setMaxResults(1);
 
-            $now = \DateTime::createFromFormat('U.u', microtime(true));
-            $redeliverLimit = (clone $now)->modify(sprintf('-%d seconds', $this->configuration['redeliver_timeout']));
             // use SELECT ... FOR UPDATE to lock table
             $doctrineEnvelope = $this->executeQuery(
                 $query->getSQL().' '.$this->driverConnection->getDatabasePlatform()->getWriteLockSQL(),
-                [
-                    ':now' => self::formatDateTime($now),
-                    ':queue_name' => $this->configuration['queue_name'],
-                    ':redeliver_limit' => self::formatDateTime($redeliverLimit),
-                ]
+                $query->getParameters()
             )->fetch();
 
             if (false === $doctrineEnvelope) {
@@ -161,6 +151,7 @@ public function get(): ?array
                 ->update($this->configuration['table_name'])
                 ->set('delivered_at', ':delivered_at')
                 ->where('id = :id');
+            $now = \DateTime::createFromFormat('U.u', microtime(true));
             $this->executeQuery($queryBuilder->getSQL(), [
                 ':id' => $doctrineEnvelope['id'],
                 ':delivered_at' => self::formatDateTime($now),
@@ -200,6 +191,33 @@ public function setup(): void
         $synchronizer->updateSchema($this->getSchema(), true);
     }
 
+    public function getMessageCount(): int
+    {
+        $queryBuilder = $this->createAvailableMessagesQueryBuilder()
+            ->select('COUNT(m.id) as message_count')
+            ->setMaxResults(1);
+
+        return $this->executeQuery($queryBuilder->getSQL(), $queryBuilder->getParameters())->fetchColumn();
+    }
+
+    private function createAvailableMessagesQueryBuilder(): QueryBuilder
+    {
+        $now = \DateTime::createFromFormat('U.u', microtime(true));
+        $redeliverLimit = (clone $now)->modify(sprintf('-%d seconds', $this->configuration['redeliver_timeout']));
+
+        return $this->driverConnection->createQueryBuilder()
+            ->select('m.*')
+            ->from($this->configuration['table_name'], 'm')
+            ->where('m.delivered_at is null OR m.delivered_at < :redeliver_limit')
+            ->andWhere('m.available_at <= :now')
+            ->andWhere('m.queue_name = :queue_name')
+            ->setParameters([
+                ':now' => self::formatDateTime($now),
+                ':queue_name' => $this->configuration['queue_name'],
+                ':redeliver_limit' => self::formatDateTime($redeliverLimit),
+            ]);
+    }
+
     private function executeQuery(string $sql, array $parameters = [])
     {
         $stmt = null;

src/Symfony/Component/Messenger/Transport/Doctrine/DoctrineReceiver.php

@@ -16,6 +16,7 @@
 use Symfony\Component\Messenger\Exception\LogicException;
 use Symfony\Component\Messenger\Exception\MessageDecodingFailedException;
 use Symfony\Component\Messenger\Exception\TransportException;
+use Symfony\Component\Messenger\Transport\Receiver\MessageCountAwareInterface;
 use Symfony\Component\Messenger\Transport\Receiver\ReceiverInterface;
 use Symfony\Component\Messenger\Transport\Serialization\PhpSerializer;
 use Symfony\Component\Messenger\Transport\Serialization\SerializerInterface;
@@ -25,7 +26,7 @@
  *
  * @experimental in 4.3
  */
-class DoctrineReceiver implements ReceiverInterface
+class DoctrineReceiver implements ReceiverInterface, MessageCountAwareInterface
 {
     private $connection;
     private $serializer;
@@ -81,6 +82,14 @@ public function reject(Envelope $envelope): void
         $this->connection->reject($this->findDoctrineReceivedStamp($envelope)->getId());
     }
 
+    /**
+     * {@inheritdoc}
+     */
+    public function getMessageCount(): int
+    {
+        return $this->connection->getMessageCount();
+    }
+
     private function findDoctrineReceivedStamp(Envelope $envelope): DoctrineReceivedStamp
     {
         /** @var DoctrineReceivedStamp|null $doctrineReceivedStamp */

src/Symfony/Component/Messenger/Transport/Receiver/MessageCountAwareInterface.php

@@ -0,0 +1,28 @@
+<?php
+
+/*
+ * This file is part of the Symfony package.
+ *
+ * (c) Fabien Potencier <fabien@symfony.com>
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+namespace Symfony\Component\Messenger\Transport\Receiver;
+
+/**
+ * @author Samuel Roze <samuel.roze@gmail.com>
+ * @author Ryan Weaver <ryan@symfonycasts.com>
+ *
+ * @experimental in 4.3
+ */
+interface MessageCountAwareInterface
+{
+    /**
+     * Returns the number of messages waiting to be handled.
+     *
+     * In some systems, this may be an approximate number.
+     */
+    public function getMessageCount(): int;
+}