spaces.php

aws/Aws/DynamoDb/LockingSessionConnection.php

@@ -0,0 +1,62 @@
+<?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(rand(
+                        $this->config['min_lock_retry_microtime'],
+                        $this->config['max_lock_retry_microtime']
+                    ));
+                } else {
+                    break;
+                }
+            }
+        }
+    }
+}