<?php
/*
* Copyright 2008 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.
*/
/**
* A persistent storage class based on the memcache, which is not
* really very persistent, as soon as you restart your memcache daemon
* the storage will be wiped, however for debugging and/or speed
* it can be useful, kinda, and cache is a lot cheaper then storage.
*
* @author Chris Chabot <chabotc@google.com>
*/
class Google_MemcacheCache extends Google_Cache {
private $connection = false;
public function __construct() {
global $apiConfig;
if (! function_exists('memcache_connect')) {
throw new Google_CacheException("Memcache functions not available");
}
$this->host = $apiConfig['ioMemCacheCache_host'];
$this->port = $apiConfig['ioMemCacheCache_port'];
if (empty($this->host) || empty($this->port)) {
throw new Google_CacheException("You need to supply a valid memcache host and port");
}
}
private function isLocked($key) {
$this->check();
if ((@memcache_get($this->connection, $key . '.lock')) === false) {
return false;
}
return true;
}
private function createLock($key) {
$this->check();
// the interesting thing is that this could fail if the lock was created in the meantime..
// but we'll ignore that out of convenience
@memcache_add($this->connection, $key . '.lock', '', 0, 5);
}
private function removeLock($key) {
$this->check();
// suppress all warnings, if some other process removed it that's ok too
@memcache_delete($this->connection, $key . '.lock');
}
private function waitForLock($key) {
$this->check();
// 20 x 250 = 5 seconds
$tries = 20;
$cnt = 0;
do {
// 250 ms is a long time to sleep, but it does stop the server from burning all resources on polling locks..
usleep(250);
$cnt ++;
} while ($cnt <= $tries && $this->isLocked($key));
if ($this->isLocked($key)) {
// 5 seconds passed, assume the owning process died off and remove it
$this->removeLock($key);
}
}
// I prefer lazy initialization since the cache isn't used every request
// so this potentially saves a lot of overhead
private function connect() {
if (! $this->connection = @memcache_pconnect($this->host, $this->port)) {
throw new Google_CacheException("Couldn't connect to memcache server");
}
}
private function check() {
if (! $this->connection) {
$this->connect();
}
}
/**
* @inheritDoc
*/
public function get($key, $expiration = false) {
$this->check();
if (($ret = @memcache_get($this->connection, $key)) === false) {
return false;
}
if (is_numeric($expiration) && (time() - $ret['time'] > $expiration)) {
$this->delete($key);
return false;
}
return $ret['data'];
}
/**
* @inheritDoc
* @param string $key
* @param string $value
* @throws Google_CacheException
*/
public function set($key, $value) {
$this->check();
// we store it with the cache_time default expiration so objects will at least get cleaned eventually.
if (@memcache_set($this->connection, $key, array('time' => time(),
'data' => $value), false) == false) {
throw new Google_CacheException("Couldn't store data in cache");
}
}
/**
* @inheritDoc
* @param String $key
*/
public function delete($key) {
$this->check();
@memcache_delete($this->connection, $key);
}
}
|
Download
