feat(Spanner): Add read write retry sample (GoogleCloudPlatform#1694)

Add Spanner read write retry sample

Author: ajupazhamayil

spanner/src/read_write_retry.php

@@ -0,0 +1,81 @@
+
+/**
+ * Copyright 2022 Google Inc.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+/**
+ * For instructions on how to run the full sample:
+ *
+ * @see https://github.com/GoogleCloudPlatform/php-docs-samples/tree/master/spanner/README.md
+ */
+
+namespace Google\Cloud\Samples\Spanner;
+
+// [START spanner_read_write_retry]
+use Google\Cloud\Spanner\SpannerClient;
+use Google\Cloud\Spanner\Transaction;
+
+/**
+ * Performs a read-write transaction to update two sample records in the
+ * database. if the transaction fails, it will retry for exactly $maxRetries times.
+ *
+ * Before running this sample, you will need to run the `update_data` sample
+ * to populate the fields.
+ * Example:
+ * ```
+ * read_write_retry($instanceId, $databaseId);
+ * ```
+ *
+ * @param string $instanceId The Spanner instance ID.
+ * @param string $databaseId The Spanner database ID.
+ */
+function read_write_retry(string $instanceId, string $databaseId): void
+{
+    $spanner = new SpannerClient();
+    $instance = $spanner->instance($instanceId);
+    $database = $instance->database($databaseId);
+    $maxRetries = 2;
+
+    $database->runTransaction(function (Transaction $t) use ($spanner) {
+        // Read the second album's budget.
+        $secondAlbumKey = [2, 2];
+        $secondAlbumKeySet = $spanner->keySet(['keys' => [$secondAlbumKey]]);
+        $secondAlbumResult = $t->read(
+            'Albums',
+            $secondAlbumKeySet,
+            ['MarketingBudget'],
+            ['limit' => 1]
+        );
+        $firstRow = $secondAlbumResult->rows()->current();
+        $secondAlbumBudget = $firstRow['MarketingBudget'];
+
+        printf('Setting second album\'s budget as the first album\'s budget.' . PHP_EOL);
+
+        // Update the row.
+        $t->updateBatch('Albums', [
+            ['SingerId' => 1, 'AlbumId' => 1, 'MarketingBudget' => $secondAlbumBudget],
+        ]);
+
+        // Commit the transaction!
+        $t->commit();
+
+        print('Transaction complete.' . PHP_EOL);
+    }, ['maxRetries' => $maxRetries]);
+}
+// [END spanner_read_write_retry]
+
+// The following 2 lines are only needed to run the samples
+require_once __DIR__ . '/../../testing/sample_helpers.php';
+\Google\Cloud\Samples\execute_sample(__FILE__, __NAMESPACE__, $argv);

spanner/test/spannerTest.php

@@ -938,6 +938,16 @@ public function testAddDropDatabaseRole()
         $this->assertStringContainsString('Revoked privileges and dropped roles new_child and new_parent ' . PHP_EOL, $output);
     }
 
+    /**
+     * @depends testUpdateData
+     */
+    public function testReadWriteRetry()
+    {
+        $output = $this->runFunctionSnippet('read_write_retry');
+        $this->assertStringContainsString('Setting second album\'s budget as the first album\'s budget.', $output);
+        $this->assertStringContainsString('Transaction complete.', $output);
+    }
+
     private function testGetInstanceConfig()
     {
         $output = $this->runFunctionSnippet('get_instance_config', [