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59 lines
1.9 KiB
59 lines
1.9 KiB
4 months ago
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<?php
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namespace Aws\DynamoDb;
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use Aws\DynamoDb\Exception\DynamoDbException;
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/**
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* The locking connection adds locking logic to the read operation.
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*/
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class LockingSessionConnection extends StandardSessionConnection
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{
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public function __construct(DynamoDbClient $client, array $config = [])
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{
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parent::__construct($client, $config);
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}
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/**
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* {@inheritdoc}
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* Retries the request until the lock can be acquired
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*/
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public function read($id)
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{
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// Create the params for the UpdateItem operation so that a lock can be
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// set and item returned (via ReturnValues) in a one, atomic operation.
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$params = [
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'TableName' => $this->getTableName(),
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'Key' => $this->formatKey($id),
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'Expected' => ['lock' => ['Exists' => false]],
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'AttributeUpdates' => ['lock' => ['Value' => ['N' => '1']]],
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'ReturnValues' => 'ALL_NEW',
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];
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// Acquire the lock and fetch the item data.
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$timeout = time() + $this->getMaxLockWaitTime();
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while (true) {
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try {
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$item = [];
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$result = $this->client->updateItem($params);
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if (isset($result['Attributes'])) {
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foreach ($result['Attributes'] as $key => $value) {
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$item[$key] = current($value);
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}
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}
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return $item;
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} catch (DynamoDbException $e) {
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if ($e->getAwsErrorCode() === 'ConditionalCheckFailedException'
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&& time() < $timeout
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) {
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usleep(rand(
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$this->getMinLockRetryMicrotime(),
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$this->getMaxLockRetryMicrotime()
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));
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} else {
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break;
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}
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}
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}
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}
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}
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