Refactor cache handler

Move functionality to FileCacheDriver, strip down manager class

qa-include/Q2A/Storage/CacheFactory.php

+<?php
+/*
+	Question2Answer by Gideon Greenspan and contributors
+	http://www.question2answer.org/
+
+	File: qa-include/Q2A/Storage/CacheManager.php
+	Description: Handler for caching system.
+
+
+	This program is free software; you can redistribute it and/or
+	modify it under the terms of the GNU General Public License
+	as published by the Free Software Foundation; either version 2
+	of the License, or (at your option) any later version.
+
+	This program is distributed in the hope that it will be useful,
+	but WITHOUT ANY WARRANTY; without even the implied warranty of
+	MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+	GNU General Public License for more details.
+
+	More about this license: http://www.question2answer.org/license.php
+*/
+
+/**
+ * Caches data (typically from database queries) to the filesystem.
+ */
+class Q2A_Storage_CacheFactory
+{
+	/**
+	 * Get the appropriate cache handler.
+	 * @return Q2A_Storage_CacheInterface The cache handler.
+	 */
+	public static function getCacheDriver()
+	{
+		$config = array(
+			'enabled' => (int) qa_opt('caching_enabled') === 1,
+			'dir' => defined('QA_CACHE_DIRECTORY') ? QA_CACHE_DIRECTORY : null,
+		);
+
+		return new Q2A_Storage_FileCacheDriver($config);
+	}
+}

qa-include/Q2A/Storage/CacheManager.php

-<?php
-/*
-	Question2Answer by Gideon Greenspan and contributors
-	http://www.question2answer.org/
-
-	File: qa-include/Q2A/Storage/CacheManager.php
-	Description: Handler for caching system.
-
-
-	This program is free software; you can redistribute it and/or
-	modify it under the terms of the GNU General Public License
-	as published by the Free Software Foundation; either version 2
-	of the License, or (at your option) any later version.
-
-	This program is distributed in the hope that it will be useful,
-	but WITHOUT ANY WARRANTY; without even the implied warranty of
-	MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
-	GNU General Public License for more details.
-
-	More about this license: http://www.question2answer.org/license.php
-*/
-
-/**
- * Caches data (typically from database queries) to the filesystem.
- */
-class Q2A_Storage_CacheManager
-{
-	private static $instance;
-	private $enabled = false;
-	private $cacheDriver;
-
-	/**
-	 * Creates a new CacheManager instance and sets up the cache driver.
-	 */
-	private function __construct()
-	{
-		if (qa_opt('caching_enabled') != 1)
-			return;
-
-		$config = array(
-			'dir' => defined('QA_CACHE_DIRECTORY') ? QA_CACHE_DIRECTORY : null,
-		);
-
-		$this->cacheDriver = new Q2A_Storage_FileCache($config);
-		$this->enabled = $this->cacheDriver->isEnabled();
-	}
-
-	/**
-	 * Initializes the class and returns the singleton.
-	 * @return Q2A_Storage_CacheManager
-	 */
-	public static function getInstance()
-	{
-		if (!isset(self::$instance)) {
-			self::$instance = new self();
-		}
-
-		return self::$instance;
-	}
-
-	/**
-	 * Get the cached data for the supplied key.
-	 * @param string $key The unique cache identifier
-	 * @return mixed The cached data, or null otherwise.
-	 */
-	public function get($key)
-	{
-		if ($this->enabled) {
-			$encData = $this->cacheDriver->get($key);
-
-			// retrieve data, ignoring any notices
-			$data = @unserialize($encData);
-			if ($data !== false) {
-				return $data;
-			}
-		}
-
-		return null;
-	}
-
-	/**
-	 * Serialize some data and store it in the cache.
-	 * @param string $key The unique cache identifier
-	 * @param mixed $data The data to cache - must be scalar values (i.e. string, int, array).
-	 * @param int $ttl Number of minutes for which to cache the data.
-	 * @return bool Whether the data was successfully cached.
-	 */
-	public function set($key, $data, $ttl)
-	{
-		if ($this->enabled) {
-			$encData = serialize($data);
-			return $this->cacheDriver->set($key, $encData, $ttl);
-		}
-
-		return false;
-	}
-
-	/**
-	 * Whether caching is available.
-	 * @return bool
-	 */
-	public function isEnabled()
-	{
-		return $this->enabled;
-	}
-
-	/**
-	 * Get the last error.
-	 * @return string
-	 */
-	public function getError()
-	{
-		return isset($this->cacheDriver) ? $this->cacheDriver->getError() : '';
-	}
-}

qa-include/Q2A/Storage/FileCache.php → qa-include/Q2A/Storage/FileCacheDriver.php

@@ -23,7 +23,7 @@
 /**
  * Caches data (typically from database queries) to the filesystem.
  */
-class Q2A_Storage_FileCache
+class Q2A_Storage_FileCacheDriver
 {
 	private $enabled = false;
 	private $error;
@@ -35,6 +35,10 @@ class Q2A_Storage_FileCache
 	 */
 	public function __construct($config)
 	{
+		if (!$config['enabled']) {
+			return;
+		}
+
 		if (isset($config['dir'])) {
 			$this->cacheDir = realpath($config['dir']);
 
@@ -58,6 +62,10 @@ class Q2A_Storage_FileCache
 	 */
 	public function get($key)
 	{
+		if (!$this->enabled) {
+			return null;
+		}
+
 		$file = $this->getFilename($key);
 
 		if (is_readable($file)) {
@@ -69,7 +77,12 @@ class Q2A_Storage_FileCache
 				$expiry = array_shift($lines);
 
 				if (is_numeric($expiry) && time() < $expiry) {
-					return implode("\n", $lines);
+					$encData = implode("\n", $lines);
+					// decode data, ignoring any notices
+					$data = @unserialize($encData);
+					if ($data !== false) {
+						return $data;
+					}
 				}
 			}
 		}
@@ -78,23 +91,24 @@ class Q2A_Storage_FileCache
 	}
 
 	/**
-	 * Store a string (usually serialized data) in the cache along with the key and expiry time.
+	 * Store something in the cache along with the key and expiry time. Data gets 'serialized' to a string before storing.
 	 * @param string $key The unique cache identifier.
-	 * @param string $str The data to cache (usually a serialized string).
+	 * @param mixed $data The data to cache (in core Q2A this is usually an array).
 	 * @param int $ttl Number of minutes for which to cache the data.
 	 * @return bool Whether the file was successfully cached.
 	 */
-	public function set($key, $str, $ttl)
+	public function set($key, $data, $ttl)
 	{
 		$success = false;
 		$ttl = (int) $ttl;
 
 		if ($this->enabled && $ttl > 0) {
-			$file = $this->getFilename($key);
-			$dir = dirname($file);
+			$encData = serialize($data);
 			$expiry = time() + ($ttl * 60);
-			$cache = $key . "\n" . $expiry . "\n" . $str;
+			$cache = $key . "\n" . $expiry . "\n" . $encData;
 
+			$file = $this->getFilename($key);
+			$dir = dirname($file);
 			if (is_dir($dir) || mkdir($dir, 0777, true)) {
 				$success = file_put_contents($file, $cache) !== false;
 			}

qa-include/pages/admin/admin-default.php

@@ -1790,8 +1790,8 @@ switch ($adminsection) {
 		break;
 
 	case 'caching':
-		$cacheManager = Q2A_Storage_CacheManager::getInstance();
-		$qa_content['error'] = $cacheManager->getError();
+		$cacheDriver = Q2A_Storage_CacheFactory::getCacheDriver();
+		$qa_content['error'] = $cacheDriver->getError();
 		break;
 }
 

qa-include/pages/question.php

@@ -42,13 +42,13 @@ $pagestate = qa_get_state();
 
 // Get information about this question
 
-$cacheHandler = Q2A_Storage_CacheManager::getInstance();
+$cacheDriver = Q2A_Storage_CacheFactory::getCacheDriver();
 $cacheKey = "page:question:$questionid";
-$useCache = $userid === null && $cacheHandler->isEnabled() && !qa_is_http_post() && empty($pagestate);
+$useCache = $userid === null && $cacheDriver->isEnabled() && !qa_is_http_post() && empty($pagestate);
 $saveCache = false;
 
 if ($useCache) {
-	$questionData = $cacheHandler->get($cacheKey);
+	$questionData = $cacheDriver->get($cacheKey);
 }
 
 if (!isset($questionData)) {
@@ -158,7 +158,7 @@ if ($permiterror && (qa_is_human_probably() || !qa_opt('allow_view_q_bots'))) {
 if ($saveCache) {
 	$questionAge = qa_opt('db_time') - $question['created'];
 	if ($questionAge > 86400 * qa_opt('caching_q_start')) {
-		$cacheHandler->set($cacheKey, $questionData, qa_opt('caching_q_time'));
+		$cacheDriver->set($cacheKey, $questionData, qa_opt('caching_q_time'));
 	}
 }
 

qa-include/qa-db.php

@@ -511,11 +511,11 @@ function qa_db_single_select($selectspec)
 {
 	// check for cached results
 	if (isset($selectspec['caching'])) {
-		$cacheHandler = Q2A_Storage_CacheManager::getInstance();
+		$cacheDriver = Q2A_Storage_CacheFactory::getCacheDriver();
 		$cacheKey = 'query:' . $selectspec['caching']['key'];
 
-		if ($cacheHandler->isEnabled()) {
-			$queryData = $cacheHandler->get($cacheKey);
+		if ($cacheDriver->isEnabled()) {
+			$queryData = $cacheDriver->get($cacheKey);
 			if ($queryData !== null)
 				return $queryData;
 		}
@@ -535,8 +535,8 @@ function qa_db_single_select($selectspec)
 
 	// save cached results
 	if (isset($selectspec['caching'])) {
-		if ($cacheHandler->isEnabled()) {
-			$cacheHandler->set($cacheKey, $results, $selectspec['caching']['ttl']);
+		if ($cacheDriver->isEnabled()) {
+			$cacheDriver->set($cacheKey, $results, $selectspec['caching']['ttl']);
 		}
 	}