143 lines
3.8 KiB
PHP
143 lines
3.8 KiB
PHP
<?php
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/*
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* Copyright 2008 Google Inc.
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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/*
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* This class implements a basic on disk storage. While that does
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* work quite well it's not the most elegant and scalable solution.
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* It will also get you into a heap of trouble when you try to run
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* this in a clustered environment.
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*
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* @author Chris Chabot <chabotc@google.com>
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*/
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class W3TCG_Google_Cache_File extends W3TCG_Google_Cache_Abstract
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{
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const MAX_LOCK_RETRIES = 10;
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private $path;
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private $fh;
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public function __construct(W3TCG_Google_Client $client)
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{
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$this->path = $client->getClassConfig($this, 'directory');
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}
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public function get($key, $expiration = false)
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{
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$storageFile = $this->getCacheFile($key);
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$data = false;
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if (!file_exists($storageFile)) {
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return false;
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}
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if ($expiration) {
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$mtime = filemtime($storageFile);
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if ((time() - $mtime) >= $expiration) {
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$this->delete($key);
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return false;
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}
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}
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if ($this->acquireReadLock($storageFile)) {
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$data = fread($this->fh, filesize($storageFile));
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$data = unserialize($data);
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$this->unlock($storageFile);
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}
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return $data;
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}
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public function set($key, $value)
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{
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$storageFile = $this->getWriteableCacheFile($key);
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if ($this->acquireWriteLock($storageFile)) {
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// We serialize the whole request object, since we don't only want the
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// responseContent but also the postBody used, headers, size, etc.
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$data = serialize($value);
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$result = fwrite($this->fh, $data);
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$this->unlock($storageFile);
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}
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}
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public function delete($key)
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{
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$file = $this->getCacheFile($key);
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if (file_exists($file) && !unlink($file)) {
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throw new W3TCG_Google_Cache_Exception("Cache file could not be deleted");
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}
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}
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private function getWriteableCacheFile($file)
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{
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return $this->getCacheFile($file, true);
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}
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private function getCacheFile($file, $forWrite = false)
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{
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return $this->getCacheDir($file, $forWrite) . '/' . md5($file);
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}
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private function getCacheDir($file, $forWrite)
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{
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// use the first 2 characters of the hash as a directory prefix
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// this should prevent slowdowns due to huge directory listings
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// and thus give some basic amount of scalability
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$storageDir = $this->path . '/' . substr(md5($file), 0, 2);
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if ($forWrite && ! is_dir($storageDir)) {
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if (! mkdir($storageDir, 0755, true)) {
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throw new W3TCG_Google_Cache_Exception("Could not create storage directory: $storageDir");
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}
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}
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return $storageDir;
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}
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private function acquireReadLock($storageFile)
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{
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return $this->acquireLock(LOCK_SH, $storageFile);
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}
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private function acquireWriteLock($storageFile)
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{
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$rc = $this->acquireLock(LOCK_EX, $storageFile);
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if (!$rc) {
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$this->delete($storageFile);
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}
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return $rc;
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}
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private function acquireLock($type, $storageFile)
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{
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$mode = $type == LOCK_EX ? "w" : "r";
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$this->fh = fopen($storageFile, $mode);
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$count = 0;
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while (!flock($this->fh, $type | LOCK_NB)) {
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// Sleep for 10ms.
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usleep(10000);
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if (++$count < self::MAX_LOCK_RETRIES) {
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return false;
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}
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}
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return true;
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}
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public function unlock($storageFile)
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{
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if ($this->fh) {
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flock($this->fh, LOCK_UN);
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}
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}
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}
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