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<?php |
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/** |
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* Copyright 2014 SURFnet bv |
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* |
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* Licensed under the Apache License, Version 2.0 (the "License"); |
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* you may not use this file except in compliance with the License. |
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* You may obtain a copy of the License at |
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* |
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* http://www.apache.org/licenses/LICENSE-2.0 |
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* |
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* Unless required by applicable law or agreed to in writing, software |
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* distributed under the License is distributed on an "AS IS" BASIS, |
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
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* See the License for the specific language governing permissions and |
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* limitations under the License. |
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*/ |
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namespace Surfnet\StepupMiddleware\CommandHandlingBundle\EventHandling; |
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use Broadway\Domain\DomainEventStreamInterface; |
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use Broadway\Domain\DomainMessage; |
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use Broadway\EventHandling\EventBusInterface; |
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use Broadway\EventHandling\EventListenerInterface; |
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use Doctrine\ORM\EntityManagerInterface; |
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use Exception; |
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class BufferedEventBus implements EventBusInterface |
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{ |
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/** |
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* @var EventListenerInterface[] |
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*/ |
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private $eventListeners = []; |
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/** |
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* @var DomainMessage[] |
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*/ |
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private $buffer = []; |
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/** |
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* Flag to ensure only one loop is publishing domain messages from the buffer. |
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* |
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* @var bool |
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*/ |
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private $isFlushing = false; |
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/** |
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* @var EntityManagerInterface |
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*/ |
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private $entityManager; |
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public function __construct(EntityManagerInterface $entityManager) |
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{ |
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$this->entityManager = $entityManager; |
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} |
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public function subscribe(EventListenerInterface $eventListener) |
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{ |
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$this->eventListeners[] = $eventListener; |
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} |
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public function publish(DomainEventStreamInterface $domainMessages) |
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{ |
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foreach ($domainMessages as $domainMessage) { |
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$this->buffer[] = $domainMessage; |
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} |
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} |
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/** |
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* Flushes the buffered domain messages to all event listeners. |
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*/ |
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public function flush() |
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{ |
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if ($this->isFlushing) { |
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// If already flushing, we're in a nested pipeline. This means that an event that is currently being |
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// handled, triggered a command. This command caused events, which are collected in the buffer. |
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// These events may only be flushed when all current events have been handled. |
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// Therefore, we return here and check if there are events in the buffer after handling all current events. |
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return; |
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} |
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$this->isFlushing = true; |
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// swap the buffer so we can still publish new events, during or after flush |
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$buffer = $this->buffer; |
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$this->buffer = []; |
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try { |
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while ($domainMessage = array_shift($buffer)) { |
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foreach ($this->eventListeners as $eventListener) { |
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$eventListener->handle($domainMessage); |
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} |
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// After handling an event, clear the entity manager to prevent collisions in Doctrine's object tracking |
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// This comes with a caveat: event listeners cannot hold references to certain entities between events |
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$this->entityManager->clear(); |
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} |
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} catch (Exception $e) { |
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$this->isFlushing = false; |
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array_splice($this->buffer, 0, 0, $buffer); |
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throw $e; |
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} |
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$this->isFlushing = false; |
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unset($buffer); |
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// if during the handling of events new events have been queued, we need to flush them |
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if (!empty($this->buffer)) { |
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$this->flush(); |
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} |
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} |
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} |
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