MongoDB Cache class added as draft.

extensions/mongodb/Cache.php

+<?php
+/**
+ * @link http://www.yiiframework.com/
+ * @copyright Copyright (c) 2008 Yii Software LLC
+ * @license http://www.yiiframework.com/license/
+ */
+
+namespace yii\mongodb;
+
+use Yii;
+use yii\base\InvalidConfigException;
+
+/**
+ * Class Cache
+ *
+ * @author Paul Klimov <klimov.paul@gmail.com>
+ * @since 2.0
+ */
+class Cache extends \yii\caching\Cache
+{
+	/**
+	 * @var Connection|string the MongoDB connection object or the application component ID of the MongoDB connection.
+	 * After the Cache object is created, if you want to change this property, you should only assign it
+	 * with a MongoDB connection object.
+	 */
+	public $db = 'mongodb';
+	/**
+	 * @var string|array the name of the MongoDB collection that stores the cache data.
+	 */
+	public $cacheCollection = 'cache';
+	/**
+	 * @var integer the probability (parts per million) that garbage collection (GC) should be performed
+	 * when storing a piece of data in the cache. Defaults to 100, meaning 0.01% chance.
+	 * This number should be between 0 and 1000000. A value 0 meaning no GC will be performed at all.
+	 **/
+	public $gcProbability = 100;
+
+	/**
+	 * Initializes the Cache component.
+	 * This method will initialize the [[db]] property to make sure it refers to a valid MongoDB connection.
+	 * @throws InvalidConfigException if [[db]] is invalid.
+	 */
+	public function init()
+	{
+		parent::init();
+		if (is_string($this->db)) {
+			$this->db = Yii::$app->getComponent($this->db);
+		}
+		if (!$this->db instanceof Connection) {
+			throw new InvalidConfigException($this->className() . "::db must be either a MongoDB connection instance or the application component ID of a MongoDB connection.");
+		}
+	}
+
+	/**
+	 * Retrieves a value from cache with a specified key.
+	 * This method should be implemented by child classes to retrieve the data
+	 * from specific cache storage.
+	 * @param string $key a unique key identifying the cached value
+	 * @return string|boolean the value stored in cache, false if the value is not in the cache or expired.
+	 */
+	protected function getValue($key)
+	{
+		$query = new Query;
+		$row = $query->select(['data'])
+			->from($this->cacheCollection)
+			->where([
+				'id' => $key,
+				'$or' => [
+					[
+						'expire' => 0
+					],
+					[
+						'expire' => ['$gt' => time()]
+					],
+				],
+			])
+			->one($this->db);
+		if (empty($row)) {
+			return false;
+		} else {
+			return $row['data'];
+		}
+	}
+
+	/**
+	 * Stores a value identified by a key in cache.
+	 * This method should be implemented by child classes to store the data
+	 * in specific cache storage.
+	 * @param string $key the key identifying the value to be cached
+	 * @param string $value the value to be cached
+	 * @param integer $expire the number of seconds in which the cached value will expire. 0 means never expire.
+	 * @return boolean true if the value is successfully stored into cache, false otherwise
+	 */
+	protected function setValue($key, $value, $expire)
+	{
+		$result = $this->db->getCollection($this->cacheCollection)
+			->update(['id' => $key], [
+				'expire' => $expire > 0 ? $expire + time() : 0,
+				'data' => $value,
+			]);
+
+		if ($result) {
+			$this->gc();
+			return true;
+		} else {
+			return $this->addValue($key, $value, $expire);
+		}
+	}
+
+	/**
+	 * Stores a value identified by a key into cache if the cache does not contain this key.
+	 * This method should be implemented by child classes to store the data
+	 * in specific cache storage.
+	 * @param string $key the key identifying the value to be cached
+	 * @param string $value the value to be cached
+	 * @param integer $expire the number of seconds in which the cached value will expire. 0 means never expire.
+	 * @return boolean true if the value is successfully stored into cache, false otherwise
+	 */
+	protected function addValue($key, $value, $expire)
+	{
+		$this->gc();
+
+		if ($expire > 0) {
+			$expire += time();
+		} else {
+			$expire = 0;
+		}
+
+		try {
+			$this->db->getCollection($this->cacheCollection)
+				->insert([
+					'id' => $key,
+					'expire' => $expire,
+					'data' => $value,
+				]);
+			return true;
+		} catch (\Exception $e) {
+			return false;
+		}
+	}
+
+	/**
+	 * Deletes a value with the specified key from cache
+	 * This method should be implemented by child classes to delete the data from actual cache storage.
+	 * @param string $key the key of the value to be deleted
+	 * @return boolean if no error happens during deletion
+	 */
+	protected function deleteValue($key)
+	{
+		$this->db->getCollection($this->cacheCollection)
+			->remove(['id' => $key]);
+		return true;
+	}
+
+	/**
+	 * Deletes all values from cache.
+	 * Child classes may implement this method to realize the flush operation.
+	 * @return boolean whether the flush operation was successful.
+	 */
+	protected function flushValues()
+	{
+		$this->db->getCollection($this->cacheCollection)
+			->remove();
+		return true;
+	}
+
+	/**
+	 * Removes the expired data values.
+	 * @param boolean $force whether to enforce the garbage collection regardless of [[gcProbability]].
+	 * Defaults to false, meaning the actual deletion happens with the probability as specified by [[gcProbability]].
+	 */
+	public function gc($force = false)
+	{
+		if ($force || mt_rand(0, 1000000) < $this->gcProbability) {
+			$this->db->getCollection($this->cacheCollection)
+				->remove([
+					'expire' => [
+						'$gt' => 0,
+						'$lt' => time(),
+					]
+				]);
+		}
+	}
+}
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tests/unit/extensions/mongodb/CacheTest.php

+<?php
+
+namespace yiiunit\extensions\mongodb;
+
+use Yii;
+use yii\mongodb\Cache;
+
+class CacheTest extends MongoDbTestCase
+{
+	/**
+	 * @var string test cache collection name.
+	 */
+	protected static $cacheCollection = '_test_cache';
+
+	protected function tearDown()
+	{
+		$this->dropCollection(static::$cacheCollection);
+		parent::tearDown();
+	}
+
+	/**
+	 * Creates test cache instance.
+	 * @return Cache cache instance.
+	 */
+	protected function createCache()
+	{
+		return Yii::createObject([
+			'class' => Cache::className(),
+			'db' => $this->getConnection(),
+			'cacheCollection' => static::$cacheCollection,
+		]);
+	}
+
+	// Tests:
+
+	public function testSet()
+	{
+		$cache = $this->createCache();
+
+		$key = 'test_key';
+		$value = 'test_value';
+		$this->assertTrue($cache->set($key, $value), 'Unable to set value!');
+	}
+}
\ No newline at end of file