缓存MEMCACHE 使用原子性操作add，实现并发锁

 1 class cacheLock{
 2     const KEY_PREFIX = ‘_lock‘;
 3     private $mc;
 4 
 5     public function __construct(){
 6         $this->mc = new dlufMemcache(‘127.0.0.1‘,11211);
 7     }
 8 
 9     /**
10      * 进行锁操作
11      * @param [type]  $lock_id
12      * @param integer $expire
13      */
14     public function Lock($lock_id,$expire=5){
15         $mkey = self::KEY_PREFIX.$lock_id; 
16         for($i = 0; $i < 10; $i++){ 
17             $flag = false;
18             try{
19                 $flag = $this->mc->add($mkey,‘1‘,$expire);
20             }catch(Exception $e){
21                 $flag = false;
22                 //log
23             }
24             if($flag){
25                 return true;
26             }else{ 
27                 //wait for 0.3 seconds
28                 usleep(300000);
29             }
30         }
31         return false;
32     }
33 
34     /**
35      * 判断锁状态
36      * @param  [type]  $lock_id
37      * @return boolean
38      */
39     public function isLock($lock_id){
40         $mkey = self::KEY_PREFIX.$lock_id;
41         $ret = $this->mc->get($mkey);
42         if(empty($ret) || $ret === false){
43             return false;
44         }
45         return true;
46     }
47 
48     /**
49      * 解锁
50      * @param  [type] $lock_id
51      * @return [type]
52      */
53     public function unLock($lock_id){
54         $mkey = self::KEY_PREFIX.$lock_id;
55         $ret = $this->mc->delete($mkey);
56         return $ret;
57     }
58 
59  }

function useLock(){
     $lockobj = new cacheLock();
     $lock = $lockobj->Lock(‘cachelock‘);
     if(!$lock){
        echo "cachelock is lock";
        return;
     }

     /*  热点代码 写在这里
      */

     $lockobj->unLock(‘cachelock‘);
}