php/src/common/sample/CacheMemcache.php

   1 <?php
   2 /**
   3  * Licensed to the Apache Software Foundation (ASF) under one
   4  * or more contributor license agreements.  See the NOTICE file
   5  * distributed with this work for additional information
   6  * regarding copyright ownership.  The ASF licenses this file
   7  * to you under the Apache License, Version 2.0 (the
   8  * "License"); you may not use this file except in compliance
   9  * with the License.  You may obtain a copy of the License at
  10  *
  11  *     http://www.apache.org/licenses/LICENSE-2.0
  12  *
  13  * Unless required by applicable law or agreed to in writing,
  14  * software distributed under the License is distributed on an
  15  * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
  16  * KIND, either express or implied.  See the License for the
  17  * specific language governing permissions and limitations
  18  * under the License.
  19  */
  20
  21
  22 /*
  23  * This class impliments memcached based caching It'll generally be more
  24  * usefull in a multi-server envirionment then the file based caching,
  25  * (in a single server setup file based caching is actually faster)
  26  */
  27 class CacheMemcache extends Cache {
  28   private $connection = false;
  29
  30   public function __construct() {
  31     if (! function_exists('memcache_connect')) {
  32       throw new CacheException("Memcache functions not available");
  33     }
  34     if (Config::get('cache_host') == '' || Config::get('cache_port') == '') {
  35       throw new CacheException("You need to configure a cache server host and port to use the memcache backend");
  36     }
  37     $this->host = Config::get('cache_host');
  38     $this->port = Config::get('cache_port');
  39   }
  40
  41   private function isLocked($key) {
  42     $this->check();
  43     if ((@memcache_get($this->connection, $key . '.lock')) === false) {
  44       return false;
  45     }
  46     return true;
  47   }
  48
  49   private function createLock($key) {
  50     $this->check();
  51     // the interesting thing is that this could fail if the lock was created in the meantime..
  52     // but we'll ignore that out of convenience
  53     @memcache_add($this->connection, $key . '.lock', '', 0, 5);
  54   }
  55
  56   private function removeLock($key) {
  57     $this->check();
  58     // suppress all warnings, if some other process removed it that's ok too
  59     @memcache_delete($this->connection, $key . '.lock');
  60   }
  61
  62   private function waitForLock($key) {
  63     $this->check();
  64     // 20 x 250 = 5 seconds
  65     $tries = 20;
  66     $cnt = 0;
  67     do {
  68       // 250 ms is a long time to sleep, but it does stop the server from burning all resources on polling locks..
  69       usleep(250);
  70       $cnt ++;
  71     } while ($cnt <= $tries && $this->isLocked());
  72     if ($this->isLocked()) {
  73       // 5 seconds passed, assume the owning process died off and remove it
  74       $this->removeLock($key);
  75     }
  76   }
  77
  78   // I prefer lazy initalization since the cache isn't used every request
  79   // so this potentially saves a lot of overhead
  80   private function connect() {
  81     if (! $this->connection = @memcache_pconnect($this->host, $this->port)) {
  82       throw new CacheException("Couldn't connect to memcache server");
  83     }
  84   }
  85
  86   private function check() {
  87     if (! $this->connection) {
  88       $this->connect();
  89     }
  90   }
  91
  92   public function get($key, $expiration = false) {
  93     $this->check();
  94     if (! $expiration) {
  95       // default to global cache time
  96       $expiration = Config::Get('cache_time');
  97     }
  98     if (($ret = @memcache_get($this->connection, $key)) === false) {
  99       return false;
 100     }
 101     if (time() - $ret['time'] > $expiration) {
 102       $this->delete($key);
 103       return false;
 104     }
 105     return $ret['data'];
 106   }
 107
 108   public function set($key, $value) {
 109     $this->check();
 110     // we store it with the cache_time default expiration so objects will atleast get cleaned eventually.
 111     if (@memcache_set($this->connection, $key, array('time' => time(),
 112         'data' => $value), false, Config::Get('cache_time')) == false) {
 113       throw new CacheException("Couldn't store data in cache");
 114     }
 115   }
 116
 117   public function delete($key) {
 118     $this->check();
 119     @memcache_delete($this->connection, $key);
 120   }
 121 }