/**
  * 连接到缓存服务
  * @return bool
  */
 public function connect()
 {
     if ($this->cache === null) {
         $this->cache = $this->getMemcache();
         if (!is_array($this->host)) {
             $this->host = array($this->host);
         }
         foreach ($this->host as $server_address) {
             if (strpos($server_address, ':') === false) {
                 $host = $server_address;
                 $port = 11211;
             } else {
                 $strs = explode(':', $server_address);
                 $host = $strs[0];
                 $port = $strs[1] ? $strs[1] : 11211;
             }
             $re = $this->cache->addServer($host, $port);
             if ($re === false) {
                 $this->logger->writeFatal("failed to add memcache server {$server_address}");
             }
         }
         return $re;
     }
     return true;
 }