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social/src/cache/apiMemcacheCache.php 3.76 KB
42868d70   andryeyev   Создал GIT
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  <?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 apiMemcacheCache extends apiCache {
    private $connection = false;
  
    public function __construct() {
      global $apiConfig;
      if (! function_exists('memcache_connect')) {
        throw new apiCacheException("Memcache functions not available");
      }
      $this->host = $apiConfig['ioMemCacheCache_host'];
      $this->port = $apiConfig['ioMemCacheCache_port'];
      if (empty($this->host) || empty($this->port)) {
        throw new apiCacheException("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 apiCacheException("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 (! $expiration || (time() - $ret['time'] > $expiration)) {
        $this->delete($key);
        return false;
      }
      return $ret['data'];
    }
  
    /**
     * @inheritDoc
     */
    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 apiCacheException("Couldn't store data in cache");
      }
    }
  
    /**
     * @inheritDoc
     */
    public function delete($key) {
      $this->check();
      @memcache_delete($this->connection, $key);
    }
  }