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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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}