Adding a custom session handler with Cloud Datastore.

src/Datastore/DatastoreSessionHandler.php

@@ -0,0 +1,197 @@
+<?php
+/**
+ * Copyright 2016 Google Inc. All Rights Reserved.
+ *
+ * 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.
+ */
+
+namespace Google\Cloud\Datastore;
+
+use Exception;
+
+/**
+ * Custom session handler backed by Cloud Datastore.
+ *
+ * {@see http://php.net/manual/en/class.sessionhandlerinterface.php}
+ *
+ * It uses the session.save_path as the Datastore namespace for isolating the
+ * session data from your application data. It replaces '/' with '_' for the
+ * namespaceId.
+ * It also uses session.name as the Datastore kind. It uses the session id as
+ * the Datastore id. By default, it does nothing on gc for reducing the cost.
+ * Pass positive value up to 1000 for $gcLimit parameter to delete entities
+ * in gc.
+ *
+ * Example:
+ * ```
+ * use Google\Cloud\Datastore\DatastoreClient;
+ * use Google\Cloud\Datastore\DatastoreSessionHandler;
+ *
+ * $handler = new DatastoreSessionHandler(new DatastoreClient());
+ * session_set_save_handler($handler, true);
+ * session_start();
+ *
+ * # Then read and write the $_SESSION array.
+ * ```
+ */
+class DatastoreSessionHandler implements \SessionHandlerInterface
+{
+    const DEFAULT_GC_LIMIT = 0;
+    const DEFAULT_KIND = 'PHPSESSID';
+    const DEFAULT_NAMESPACE_ID = 'sessions';
+
+    /* @var int */
+    private $gcLimit;
+
+    /* @var DatastoreClient */
+    private $datastore;
+
+    /* @var string */
+    private $kind;
+
+    /* @var string */
+    private $namespaceId;
+
+    /* @var Transaction */
+    private $transaction;
+
+    /**
+     * @param DatastoreClient $datastore Datastore client
+     * @param int $gcLimit A number of entities to delete in garbage collection
+     */
+    public function __construct(
+        DatastoreClient $datastore,
+        $gcLimit = self::DEFAULT_GC_LIMIT
+    ) {
+        $this->datastore = $datastore;
+        // Cut down to 1000
+        $this->gcLimit = min($gcLimit, 1000);
+        $this->kind = self::DEFAULT_KIND;
+        $this->namespaceId = self::DEFAULT_NAMESPACE_ID;
+    }
+
+    public function open($savePath, $sessionName)
+    {
+        $this->kind = $sessionName;
+        $this->namespaceId = str_replace('/', '_', $savePath);
+        $this->transaction = $this->datastore->transaction();
+        return true;
+    }
+
+    public function close()
+    {
+        return true;
+    }
+
+    public function read($id)
+    {
+        try {
+            $key = $this->datastore->key(
+                $this->kind,
+                $id,
+                ['namespaceId' => $this->namespaceId]
+            );
+            $entity = $this->transaction->lookup($key);
+            if ($entity !== null && isset($entity['data'])) {
+                return $entity['data'];
+            }
+        } catch (Exception $e) {
+            trigger_error(
+                sprintf('Datastore lookup failed: %s', $e->getMessage()),
+                E_USER_NOTICE
+            );
+        }
+        return '';
+    }
+
+    public function write($id, $data)
+    {
+        try {
+            $key = $this->datastore->key(
+                $this->kind,
+                $id,
+                ['namespaceId' => $this->namespaceId]
+            );
+            $entity = $this->datastore->entity(
+                $key,
+                [
+                    'data' => $data,
+                    't' => time()
+                ]
+            );
+            $this->transaction->upsert($entity);
+            $this->transaction->commit();
+        } catch (Exception $e) {
+            trigger_error(
+                sprintf('Datastore upsert failed: %s', $e->getMessage()),
+                E_USER_NOTICE
+            );
+            return false;
+        }
+        return true;
+    }
+
+    public function destroy($id)
+    {
+        try {
+            $key = $this->datastore->key(
+                $this->kind,
+                $id,
+                ['namespaceId' => $this->namespaceId]
+            );
+            $this->transaction->delete($key);
+            $this->transaction->commit();
+        } catch (Exception $e) {
+            trigger_error(
+                sprintf('Datastore delete failed: %s', $e->getMessage()),
+                E_USER_NOTICE
+            );
+            return false;
+        }
+        return true;
+    }
+
+    public function gc($maxlifetime)
+    {
+        if ($this->gcLimit === 0) {
+            return true;
+        }
+        try {
+            $query = $this->datastore->query()
+                ->kind($this->kind)
+                ->filter('t', '<', time() - $maxlifetime)
+                ->order('t')
+                ->keysOnly()
+                ->limit($this->gcLimit);
+            $result = $this->datastore->runQuery(
+                $query,
+                ['namespaceId' => $this->namespaceId]
+            );
+            $keys = [];
+            /* @var Entity $e */
+            foreach ($result as $e) {
+                $keys[] = $e->key();
+            }
+            if (!empty($keys)) {
+                $this->datastore->deleteBatch($keys);
+            }
+        } catch (Exception $e) {
+            trigger_error(
+                sprintf('Session gc failed: %s', $e->getMessage()),
+                E_USER_NOTICE
+            );
+            return false;
+        }
+        return true;
+    }
+}