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<?php |
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declare(strict_types=1); |
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/* |
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* This file is part of the Explicit Architecture POC, |
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* which is created on top of the Symfony Demo application. |
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* |
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* (c) Herberto Graça <[email protected]> |
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* |
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* For the full copyright and license information, please view the LICENSE |
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* file that was distributed with this source code. |
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*/ |
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namespace Acme\App\Infrastructure\EventDispatcher; |
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use Acme\App\Core\Port\EventDispatcher\BufferedEventDispatcherInterface; |
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use Acme\App\Core\Port\Lock\LockManagerInterface; |
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use Acme\App\Core\Port\Persistence\TransactionServiceInterface; |
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use Acme\App\Core\SharedKernel\Port\EventDispatcher\EventInterface; |
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use Acme\PhpExtension\Helper\TypeHelper; |
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use Acme\PhpExtension\ObjectDispatcher\AbstractDispatcher; |
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use Psr\Log\LoggerInterface; |
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use Psr\Log\NullLogger; |
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use Throwable; |
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/** |
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* Conceptually, the code triggering an event must not rely on the logic that the event triggers. So that logic doesn't |
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* need to, and should not, be executed in-line with the code triggering it. |
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* This means that, technically, all events could be asynchronous, meaning that the logic they trigger could be |
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* executed after the HTTP request has been handled and the HTTP response was sent back to the client. Ideally in |
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* another process, started by a message bus/queue. |
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* However, for UX reasons, sometimes we want to handle an event in the same request where it is triggered, so that we |
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* make sure the user can see the expected results in the next request he makes. |
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* |
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* Thus, we have the need for two types of event dispatchers (which can be behind a proxy dispatcher): |
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* - A SyncEventDispatcher which dispatcher the events in the same request |
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* - An AsyncEventDispatcher, which sends the events to a message bus so they will be executed later, in parallel |
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* |
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* Nevertheless, despite the SyncEventDispatcher running the event listeners in the same HTTP request as the code that |
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* triggered the events, it does not mean it must run those listeners in-line with the code that triggered the events. |
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* Thus, this SyncEventDispatcher will put the events in a buffer, and it will flush them all to the listeners after |
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* the system handles the HTTP request, and just before sending the HTTP response back to the client. |
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*/ |
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final class SyncEventDispatcher extends AbstractDispatcher implements BufferedEventDispatcherInterface |
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{ |
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/** |
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* @var [EventInterface,[]][] |
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*/ |
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private $eventBuffer = []; |
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/** |
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* @var TransactionServiceInterface |
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*/ |
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private $transactionService; |
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/** |
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* @var LockManagerInterface |
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*/ |
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private $lockManager; |
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/** |
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* @var LoggerInterface |
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*/ |
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private $logger; |
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public function __construct( |
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TransactionServiceInterface $transactionService, |
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LockManagerInterface $lockManager, |
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LoggerInterface $logger = null |
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) { |
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$this->transactionService = $transactionService; |
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$this->lockManager = $lockManager; |
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$this->logger = $logger ?? new NullLogger(); |
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} |
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public function dispatch(EventInterface $event, array $metadata = []): void |
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{ |
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$this->eventBuffer[] = [$event, $metadata]; |
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} |
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public function flush(): void |
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{ |
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foreach ($this->eventBuffer as [$event, $metadata]) { |
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foreach ($this->getDestinationListForObject(\get_class($event)) as $listener) { |
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/* |
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* Since these events are going to be handled outside of the main use case transaction, |
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* they will also be executed outside of the request transaction (after it is closed) so we will need |
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* to open a new transaction for the event listeners. |
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* Furthermore, since each event is independent from each other, we need to open a new transaction |
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* for each individual event listener. |
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*/ |
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try { |
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$this->transactionService->startTransaction(); |
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$listener($event, $metadata); |
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$this->transactionService->finishTransaction(); |
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} catch (Throwable $e) { |
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/* |
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* We simply log the exception and continue because if we rethrow the exception, the remaining |
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* event listeners will not be triggered. |
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*/ |
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$this->logger->error( |
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'Error occurred while handling event \'' . TypeHelper::getType($event) |
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. "' with listener '" . TypeHelper::getType($listener) . "'.\n" |
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. 'Exception message: ' . $e->getMessage() . "\n" |
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. 'Exception trace: ' . $e->getTraceAsString() . "\n" |
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); |
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$this->transactionService->rollbackTransaction(); |
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} finally { |
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// We release all locks here, so that they can be reacquired when processing the next event |
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$this->lockManager->releaseAll(); |
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} |
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} |
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} |
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} |
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public function reset(): void |
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{ |
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$this->eventBuffer = []; |
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} |
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} |
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hgraca /
explicit-architecture-php
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This check marks access to variables or properties that have not been declared yet. While PHP has no explicit notion of declaring a variable, accessing it before a value is assigned to it is most likely a bug.