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File: application/modules/extensions/aws/Aws/DynamoDb/LockingSessionConnection.php

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File: application/modules/extensions/aws/Aws/DynamoDb/LockingSessionConnection.php
Role: Application script
Content type: text/plain
Description: Application script
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<?php
namespace Aws\DynamoDb;

use
Aws\DynamoDb\Exception\DynamoDbException;

/**
 * The locking connection adds locking logic to the read operation.
 */
class LockingSessionConnection extends StandardSessionConnection
{
    public function
__construct(DynamoDbClient $client, array $config = [])
    {
       
parent::__construct($client, $config + [
           
'max_lock_wait_time' => 10,
           
'min_lock_retry_microtime' => 10000,
           
'max_lock_retry_microtime' => 50000,
        ]);
    }

   
/**
     * {@inheritdoc}
     * Retries the request until the lock can be acquired
     */
   
public function read($id)
    {
       
// Create the params for the UpdateItem operation so that a lock can be
        // set and item returned (via ReturnValues) in a one, atomic operation.
       
$params = [
           
'TableName' => $this->config['table_name'],
           
'Key' => $this->formatKey($id),
           
'Expected' => ['lock' => ['Exists' => false]],
           
'AttributeUpdates' => ['lock' => ['Value' => ['N' => '1']]],
           
'ReturnValues' => 'ALL_NEW',
        ];

       
// Acquire the lock and fetch the item data.
       
$timeout = time() + $this->config['max_lock_wait_time'];
        while (
true) {
            try {
               
$item = [];
               
$result = $this->client->updateItem($params);
                if (isset(
$result['Attributes'])) {
                    foreach (
$result['Attributes'] as $key => $value) {
                       
$item[$key] = current($value);
                    }
                }
                return
$item;
            } catch (
DynamoDbException $e) {
                if (
$e->getAwsErrorCode() === 'ConditionalCheckFailedException'
                   
&& time() < $timeout
               
) {
                   
usleep(pow(10, -6) * rand(
                       
$this->config['min_lock_retry_microtime'],
                       
$this->config['max_lock_retry_microtime']
                    ));
                } else {
                    break;
                }
            }
        }
    }
}