AmqpMessageHandler::__construct() - Code Metrics - Inspection of "add branch alias to composer.json" - Werkspot/message-queue - Measure and Improve Code Quality continuously with Scrutinizer

Failed Conditions

Push — bkp ( 3b4b05 )

by Herberto

created 2017-09-19 12:14 UTC

AmqpMessageHandler::__construct() A

↳ Parent: AmqpMessageHandler

Complexity

Conditions	1
Paths	1

Size

Total Lines	10
Code Lines	4

Duplication

Lines	0
Ratio	0 %

Code Coverage

Tests	5
CRAP Score	1

Importance

Changes

Metric	Value
dl	0
loc	10
ccs	5
cts	5
cp	1
rs	9.4285
c	0
b	0
f	0
cc	1
eloc	4
nc	1
nop	4
crap	1

<?php

namespace Werkspot\MessageQueue\DeliveryQueue\Amqp;

use DateTime;
use PhpAmqpLib\Message\AMQPMessage;
use Psr\Log\LoggerInterface;
use Psr\Log\NullLogger;
use Psr\SimpleCache\CacheInterface;
use Werkspot\MessageQueue\DeliveryQueue\Exception\AlreadyClaimedException;
use Werkspot\MessageQueue\DeliveryQueue\Exception\CanNotClaimException;
use Werkspot\MessageQueue\DeliveryQueue\Exception\UnrecoverablePersistenceException;
use Werkspot\MessageQueue\DeliveryQueue\MessageHandlerInterface;
use Werkspot\MessageQueue\DeliveryQueue\PersistenceClientInterface;
use Werkspot\MessageQueue\Message\MessageInterface;

final class AmqpMessageHandler implements AmqpMessageHandlerInterface
{
    const CLAIM_TTL = 3600;
    const UNPACKING_EXCEPTION_MSG_UNSERIALIZABLE_CONTENT = 'It was not possible to unserialize the AmqpMessage contents.';
    const UNPACKING_EXCEPTION_MSG_UNEXPECTED_TYPE = 'The AmqpMessage content is not a MessageQueue MessageInterface.';

    /**
     * @var MessageHandlerInterface
     */
    private $handler;

    /**
     * @var CacheInterface
     */
    private $cache;

    /**
     * @var LoggerInterface
     */
    private $logger;

    /**
     * @var PersistenceClientInterface
     */
    private $persistenceClient;

    /**
     * @var bool
     */
    private $hasRegisteredShutdownHandler = false;

    /**
     * @var AMQPMessage
     */
    private $amqpMessage;

    public function __construct(
        MessageHandlerInterface $handler,
        CacheInterface $cache,
        PersistenceClientInterface $persistenceClient,
        LoggerInterface $logger = null
    ) {
        $this->handler = $handler;
        $this->cache = $cache;
        $this->persistenceClient = $persistenceClient;
        $this->logger = $logger ?? new NullLogger();
    }

    public function handle(AMQPMessage $amqpMessage): void
    {
        $this->initiateHandling($amqpMessage);
        $this->registerShutdownHandler();

        // RabbitMQ can and WILL send duplicate messages to clients. You are recommended to handle message in an
        // idempotent way, but for us this is not really possible, because sending out emails is never idempotent.
        // So we are doing the next best thing, deduplicating them.
        //
        // When deduplicating them we should do it as early as possible and in the most performing way as possible to
        // prevent race conditions where 2 consumers get the message at near the same time. So make sure we deduplicate
        // as soon as possible to keep the duplicate executing at a minimum.
        //
        // See: https://www.rabbitmq.com/reliability.html#consumer
        //  > [..] messages can be duplicated, and consumers must be prepared to handle them. If possible, ensure that
        //  > your consumers handle messages in an idempotent way rather than explicitly deal with deduplication.

        try {
            $this->claim($amqpMessage);
        } catch (AlreadyClaimedException $e) {
            $this->logAlreadyClaimedMessage($amqpMessage);
            // If we already processed it, we should still ack it here, otherwise rabbit will try to do it again, which
            // is exactly what we don't want.
            $this->acknowledgeMessage($amqpMessage);
            $this->terminateHandling();
            return;
        } catch (CanNotClaimException $e) {
            $this->logger->notice($e->getMessage());
            // if we don't have a message ID we can not claim it nor deduplicate it so
            // we should always process it, just to be sure we don't lose a message
        }

        try {
            $this->handler->handle($this->unpack($amqpMessage));
            $this->acknowledgeMessage($amqpMessage);
        } catch (AmqpMessageUnpackingException $e) {
            $this->logger->warning($e->getMessage());
            $this->persistenceClient->persistUndeliverableMessage($amqpMessage->body, $e->getMessage());
            $this->acknowledgeMessage($amqpMessage);
        } catch (UnrecoverablePersistenceException $e) {
            $this->logger->warning($e->getMessage());
            $this->acknowledgeMessage($amqpMessage);
            throw $e;
        } finally {
            $this->terminateHandling();
        }
        // We do not acknowledge the amqp msg when there was any other exception because if we could not put the msg
        // back in the scheduled queue, we would lose the message. This way it stays in rabbitMq and is tried again.
    }

    public function shutdownHandler(): void
    {
        if (!$this->isHandlingMessage()) {
            return;
        }

        $this->handler->shutdown();

        $this->acknowledgeMessage($this->amqpMessage);
    }

    private function registerShutdownHandler(): void
    {
        // The only way to catch (all) fatal errors is to have a shutdownHandler
        // This piece of code for example will not throw a Throwable, but just kill the php script:
        // ```
        //   $client = new SoapClient(null, ['location' => "http://localhost/soap.php", 'uri' => "http://test-uri/"]);
        //   $client->__setSoapHeaders([0 => null]);
        // ```
        //
        // But this is a big problem, because in that case we would not send an 'ACK' back to rabbit, as the fatal
        // error would just kill the php script, so rabbit would try again with the next available worker (as the
        // connection was hard interrupted).
        //
        // So if it fails again in the next worker with a fatal error again we get an endless retry loop in rabbit
        // which will basically break the queue, as nothing else is processed except for endlessly retrying the fatal.
        //
        // To remedy this we register the shutdown handler, we add the fatal error message to the command, and store
        // it in the queue to try again after the normal retry period, finally we send the ACK to rabbit, as we've
        // dealt with it properly (we will retry it in the future, and have logged the error nicely in the queue).
        if (!$this->hasRegisteredShutdownHandler) {
            register_shutdown_function([$this, 'shutdownHandler']);
            $this->hasRegisteredShutdownHandler = true;
        }
    }

    /**
     * @throws AlreadyClaimedException
     * @throws CanNotClaimException
     */
    private function claim(AMQPMessage $amqpMessage): void
    {
        if (!$amqpMessage->has('message_id')) {
            throw new CanNotClaimException(
                'Could not claim AMQP message because it does not have a message ID. Message body: '
                . $amqpMessage->body
            );
        }

        $cacheKey = 'msg_handled.' . $amqpMessage->get('message_id');

        if ($this->cache->has($cacheKey)) {
            throw new AlreadyClaimedException('AMQP message has already been claimed, with cache key ' . $cacheKey);
        }

        $this->cache->set($cacheKey, true, self::CLAIM_TTL);
    }

    private function acknowledgeMessage(AMQPMessage $amqpMessage): void
    {
        $channel = $amqpMessage->delivery_info['channel'];
        $channel->basic_ack($amqpMessage->delivery_info['delivery_tag']);
    }

    private function unpack(AMQPMessage $amqpMessage): MessageInterface
    {
        $result = @unserialize($amqpMessage->body);

        if ($result === false) {
            throw new AmqpMessageUnpackingException(self::UNPACKING_EXCEPTION_MSG_UNSERIALIZABLE_CONTENT);
        }

        if (! $result instanceof MessageInterface) {
            throw new AmqpMessageUnpackingException(self::UNPACKING_EXCEPTION_MSG_UNEXPECTED_TYPE);
        }

        return $result;
    }

    private function getLogMessage(MessageInterface $message): string

    {
        return $message->getId()
            . ', ' . $message->getDestination()
            . ', ' . $message->getDeliverAt()->format(DateTime::ATOM)
            . ', ' . $message->getCreatedAt()->format(DateTime::ATOM)
            . ', ' . $message->getUpdatedAt()->format(DateTime::ATOM)
            . ', ' . $message->getTries()
            . ', ' . $message->getPriority()
            . ', ' . $this->getPayloadDescription($message);
    }

    private function getPayloadDescription(MessageInterface $message): string

    {
        if (is_object($message->getPayload())) {
            return get_class($message->getPayload());
        }

        if (is_array($message->getPayload())) {
            return 'array';
        }

        return (string) $message->getPayload();
    }

    /**
     * @param AMQPMessage $amqpMessage
     *
     */
    private function logAlreadyClaimedMessage(AMQPMessage $amqpMessage): void
    {
        $queuedMessage = $this->unpack($amqpMessage);

        $message = 'Queue message was already claimed: ' . $this->getLogMessage($queuedMessage);

        $this->logger->notice($message);
    }

    private function initiateHandling(AMQPMessage $amqpMessage): void
    {
        $this->amqpMessage = $amqpMessage;
    }

    private function terminateHandling(): void
    {
        $this->amqpMessage = null;
    }

    public function isHandlingMessage(): bool
    {
        return $this->amqpMessage !== null;
    }
}


1			<?php
2
3			namespace Werkspot\MessageQueue\DeliveryQueue\Amqp;
4
5			use DateTime;
6			use PhpAmqpLib\Message\AMQPMessage;
7			use Psr\Log\LoggerInterface;
8			use Psr\Log\NullLogger;
9			use Psr\SimpleCache\CacheInterface;
10			use Werkspot\MessageQueue\DeliveryQueue\Exception\AlreadyClaimedException;
11			use Werkspot\MessageQueue\DeliveryQueue\Exception\CanNotClaimException;
12			use Werkspot\MessageQueue\DeliveryQueue\Exception\UnrecoverablePersistenceException;
13			use Werkspot\MessageQueue\DeliveryQueue\MessageHandlerInterface;
14			use Werkspot\MessageQueue\DeliveryQueue\PersistenceClientInterface;
15			use Werkspot\MessageQueue\Message\MessageInterface;
16
17			final class AmqpMessageHandler implements AmqpMessageHandlerInterface
18			{
19			const CLAIM_TTL = 3600;
20			const UNPACKING_EXCEPTION_MSG_UNSERIALIZABLE_CONTENT = 'It was not possible to unserialize the AmqpMessage contents.';
21			const UNPACKING_EXCEPTION_MSG_UNEXPECTED_TYPE = 'The AmqpMessage content is not a MessageQueue MessageInterface.';
22
23			/**
24			* @var MessageHandlerInterface
25			*/
26			private $handler;
27
28			/**
29			* @var CacheInterface
30			*/
31			private $cache;
32
33			/**
34			* @var LoggerInterface
35			*/
36			private $logger;
37
38			/**
39			* @var PersistenceClientInterface
40			*/
41			private $persistenceClient;
42
43			/**
44			* @var bool
45			*/
46			private $hasRegisteredShutdownHandler = false;
47
48			/**
49			* @var AMQPMessage
50			*/
51			private $amqpMessage;
52
53	7		public function __construct(
54			MessageHandlerInterface $handler,
55			CacheInterface $cache,
56			PersistenceClientInterface $persistenceClient,
57			LoggerInterface $logger = null
58			) {
59	7		$this->handler = $handler;
60	7		$this->cache = $cache;
61	7		$this->persistenceClient = $persistenceClient;
62	7		$this->logger = $logger ?? new NullLogger();
63	7		}
64
65	7		public function handle(AMQPMessage $amqpMessage): void
66			{
67	7		$this->initiateHandling($amqpMessage);
68	7		$this->registerShutdownHandler();
69
70			// RabbitMQ can and WILL send duplicate messages to clients. You are recommended to handle message in an
71			// idempotent way, but for us this is not really possible, because sending out emails is never idempotent.
72			// So we are doing the next best thing, deduplicating them.
73			//
74			// When deduplicating them we should do it as early as possible and in the most performing way as possible to
75			// prevent race conditions where 2 consumers get the message at near the same time. So make sure we deduplicate
76			// as soon as possible to keep the duplicate executing at a minimum.
77			//
78			// See: https://www.rabbitmq.com/reliability.html#consumer
79			// > [..] messages can be duplicated, and consumers must be prepared to handle them. If possible, ensure that
80			// > your consumers handle messages in an idempotent way rather than explicitly deal with deduplication.
81
82			try {
83	7		$this->claim($amqpMessage);
84	2		} catch (AlreadyClaimedException $e) {
85	1		$this->logAlreadyClaimedMessage($amqpMessage);
86			// If we already processed it, we should still ack it here, otherwise rabbit will try to do it again, which
87			// is exactly what we don't want.
88	1		$this->acknowledgeMessage($amqpMessage);
89	1		$this->terminateHandling();
90	1		return;
91	1		} catch (CanNotClaimException $e) {
92	1		$this->logger->notice($e->getMessage());
93			// if we don't have a message ID we can not claim it nor deduplicate it so
94			// we should always process it, just to be sure we don't lose a message
95			}
96
97			try {
98	6		$this->handler->handle($this->unpack($amqpMessage));
99	1		$this->acknowledgeMessage($amqpMessage);
100	5		} catch (AmqpMessageUnpackingException $e) {
101	3		$this->logger->warning($e->getMessage());
102	3		$this->persistenceClient->persistUndeliverableMessage($amqpMessage->body, $e->getMessage());
103	3		$this->acknowledgeMessage($amqpMessage);
104	2		} catch (UnrecoverablePersistenceException $e) {
105	1		$this->logger->warning($e->getMessage());
106	1		$this->acknowledgeMessage($amqpMessage);
107	1		throw $e;
108	4		} finally {
109	6		$this->terminateHandling();
110			}
111			// We do not acknowledge the amqp msg when there was any other exception because if we could not put the msg
112			// back in the scheduled queue, we would lose the message. This way it stays in rabbitMq and is tried again.
113	4		}
114
115			public function shutdownHandler(): void
116			{
117			if (!$this->isHandlingMessage()) {
118			return;
119			}
120
121			$this->handler->shutdown();
122
123			$this->acknowledgeMessage($this->amqpMessage);
124			}
125
126	7		private function registerShutdownHandler(): void
127			{
128			// The only way to catch (all) fatal errors is to have a shutdownHandler
129			// This piece of code for example will not throw a Throwable, but just kill the php script:
130			// ```
131			// $client = new SoapClient(null, ['location' => "http://localhost/soap.php", 'uri' => "http://test-uri/"]);
132			// $client->__setSoapHeaders([0 => null]);
133			// ```
134			//
135			// But this is a big problem, because in that case we would not send an 'ACK' back to rabbit, as the fatal
136			// error would just kill the php script, so rabbit would try again with the next available worker (as the
137			// connection was hard interrupted).
138			//
139			// So if it fails again in the next worker with a fatal error again we get an endless retry loop in rabbit
140			// which will basically break the queue, as nothing else is processed except for endlessly retrying the fatal.
141			//
142			// To remedy this we register the shutdown handler, we add the fatal error message to the command, and store
143			// it in the queue to try again after the normal retry period, finally we send the ACK to rabbit, as we've
144			// dealt with it properly (we will retry it in the future, and have logged the error nicely in the queue).
145	7		if (!$this->hasRegisteredShutdownHandler) {
146			register_shutdown_function([$this, 'shutdownHandler']);
147			$this->hasRegisteredShutdownHandler = true;
148			}
149	7		}
150
151			/**
152			* @throws AlreadyClaimedException
153			* @throws CanNotClaimException
154			*/
155	7		private function claim(AMQPMessage $amqpMessage): void
156			{
157	7		if (!$amqpMessage->has('message_id')) {
158	1		throw new CanNotClaimException(
159			'Could not claim AMQP message because it does not have a message ID. Message body: '
160	1		. $amqpMessage->body
161			);
162			}
163
164	6		$cacheKey = 'msg_handled.' . $amqpMessage->get('message_id');
165
166	6		if ($this->cache->has($cacheKey)) {
167	1		throw new AlreadyClaimedException('AMQP message has already been claimed, with cache key ' . $cacheKey);
168			}
169
170	5		$this->cache->set($cacheKey, true, self::CLAIM_TTL);
171	5		}
172
173	6		private function acknowledgeMessage(AMQPMessage $amqpMessage): void
174			{
175	6		$channel = $amqpMessage->delivery_info['channel'];
176	6		$channel->basic_ack($amqpMessage->delivery_info['delivery_tag']);
177	6		}
178
179	7		private function unpack(AMQPMessage $amqpMessage): MessageInterface
180			{
181	7		$result = @unserialize($amqpMessage->body);
182
183	7		if ($result === false) {
184	2		throw new AmqpMessageUnpackingException(self::UNPACKING_EXCEPTION_MSG_UNSERIALIZABLE_CONTENT);
185			}
186
187	5		if (! $result instanceof MessageInterface) {
188	1		throw new AmqpMessageUnpackingException(self::UNPACKING_EXCEPTION_MSG_UNEXPECTED_TYPE);
189			}
190
191	4		return $result;
192			}
193
194	1	View Code Duplication	private function getLogMessage(MessageInterface $message): string
			0 ignored issues – show Duplication introduced 2017-09-08 12:33 UTC by Report Bug Copy Issue Report This method seems to be duplicated in your project. Duplicated code is one of the most pungent code smells. If you need to duplicate the same code in three or more different places, we strongly encourage you to look into extracting the code into a single class or operation. You can also find more detailed suggestions in the “Code” section of your repository. Loading history...
195			{
196	1		return $message->getId()
197	1		. ', ' . $message->getDestination()
198	1		. ', ' . $message->getDeliverAt()->format(DateTime::ATOM)
199	1		. ', ' . $message->getCreatedAt()->format(DateTime::ATOM)
200	1		. ', ' . $message->getUpdatedAt()->format(DateTime::ATOM)
201	1		. ', ' . $message->getTries()
202	1		. ', ' . $message->getPriority()
203	1		. ', ' . $this->getPayloadDescription($message);
204			}
205
206	1	View Code Duplication	private function getPayloadDescription(MessageInterface $message): string
			1 ignored issue – show Duplication introduced 2017-09-19 11:07 UTC by Report Bug Copy Issue Report This method seems to be duplicated in your project. Duplicated code is one of the most pungent code smells. If you need to duplicate the same code in three or more different places, we strongly encourage you to look into extracting the code into a single class or operation. You can also find more detailed suggestions in the “Code” section of your repository. Loading history...
207			{
208	1		if (is_object($message->getPayload())) {
209			return get_class($message->getPayload());
210			}
211
212	1		if (is_array($message->getPayload())) {
213			return 'array';
214			}
215
216	1		return (string) $message->getPayload();
217			}
218
219			/**
220			* @param AMQPMessage $amqpMessage
221			*
222			*/
223	1		private function logAlreadyClaimedMessage(AMQPMessage $amqpMessage): void
224			{
225	1		$queuedMessage = $this->unpack($amqpMessage);
226
227	1		$message = 'Queue message was already claimed: ' . $this->getLogMessage($queuedMessage);
228
229	1		$this->logger->notice($message);
230	1		}
231
232	7		private function initiateHandling(AMQPMessage $amqpMessage): void
233			{
234	7		$this->amqpMessage = $amqpMessage;
235	7		}
236
237	7		private function terminateHandling(): void
238			{
239	7		$this->amqpMessage = null;
240	7		}
241
242			public function isHandlingMessage(): bool
243			{
244			return $this->amqpMessage !== null;
245			}
246			}
247

Werkspot / message-queue

Push — bkp ( 3b4b05 )

AmqpMessageHandler::__construct() A

Complexity

Size

Duplication

Code Coverage

Importance

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