缓存MEMCACHE 使用原子性操作add，实现并发锁

发布时间：2020-05-25 03:15:31 所属栏目：PHP 来源：互联网

导读：memcache中Memcache::add()方法在缓存服务器之前不存在key时，以key作为key存储一个变量var到缓存服务器。我们使用add来向服务器添加一个键值对应，如果成功则添加，否则说明存在另一个并发作业在进行操作。通过add的原子性来判断是否要执行热点代码。具体代

memcache中Memcache::add()方法在缓存服务器之前不存在时，以作为key存储一个变量到缓存服务器。我们使用add来向服务器添加一个键值对应，如果成功则添加，否则说明存在另一个并发作业在进行操作。通过add的原子性来判断是否要执行热点代码。具体代码需结合上一篇的php使用memcache。使用该方法控制并发需要



 KEY_PREFIX = '_lock' </span><span style="color: #0000ff"&gt;public</span> <span style="color: #0000ff"&gt;function</span><span style="color: #000000"&gt; __construct(){
    </span><span style="color: #800080"&gt;$this</span>->mc = <span style="color: #0000ff"&gt;new</span> dlufMemcache('127.0.0.1',11211<span style="color: #000000"&gt;);
}

</span><span style="color: #008000"&gt;/*</span><span style="color: #008000"&gt;*
 * 进行锁操作
 * @param [type]  $lock_id
 * @param integer $expire
 </span><span style="color: #008000"&gt;*/</span>
<span style="color: #0000ff"&gt;public</span> <span style="color: #0000ff"&gt;function</span> Lock(<span style="color: #800080"&gt;$lock_id</span>,<span style="color: #800080"&gt;$expire</span>=5<span style="color: #000000"&gt;){
    </span><span style="color: #800080"&gt;$mkey</span> = self::KEY_PREFIX.<span style="color: #800080"&gt;$lock_id</span><span style="color: #000000"&gt;; 
    </span><span style="color: #0000ff"&gt;for</span>(<span style="color: #800080"&gt;$i</span> = 0; <span style="color: #800080"&gt;$i</span> < 10; <span style="color: #800080"&gt;$i</span>++<span style="color: #000000"&gt;){ 
        </span><span style="color: #800080"&gt;$flag</span> = <span style="color: #0000ff"&gt;false</span><span style="color: #000000"&gt;;
        </span><span style="color: #0000ff"&gt;try</span><span style="color: #000000"&gt;{
            </span><span style="color: #800080"&gt;$flag</span> = <span style="color: #800080"&gt;$this</span>->mc->add(<span style="color: #800080"&gt;$mkey</span>,'1',<span style="color: #800080"&gt;$expire</span><span style="color: #000000"&gt;);
        }</span><span style="color: #0000ff"&gt;catch</span>(<span style="color: #0000ff"&gt;Exception</span> <span style="color: #800080"&gt;$e</span><span style="color: #000000"&gt;){
            </span><span style="color: #800080"&gt;$flag</span> = <span style="color: #0000ff"&gt;false</span><span style="color: #000000"&gt;;
            </span><span style="color: #008000"&gt;//</span><span style="color: #008000"&gt;log</span>
<span style="color: #000000">            }

<span style="color: #0000ff">if(<span style="color: #800080">$flag<span style="color: #000000">){

<span style="color: #0000ff">return <span style="color: #0000ff">true<span style="color: #000000">;

}<span style="color: #0000ff">else<span style="color: #000000">{

<span style="color: #008000">//<span style="color: #008000">wait for 0.3 seconds

<span style="color: #008080">usleep(300000<span style="color: #000000">);

}

}

<span style="color: #0000ff">return <span style="color: #0000ff">false<span style="color: #000000">;

}
</span><span style="color: #008000"&gt;/*</span><span style="color: #008000"&gt;*
 * 判断锁状态
 * @param  [type]  $lock_id
 * @return boolean
 </span><span style="color: #008000"&gt;*/</span>
<span style="color: #0000ff"&gt;public</span> <span style="color: #0000ff"&gt;function</span> isLock(<span style="color: #800080"&gt;$lock_id</span><span style="color: #000000"&gt;){
    </span><span style="color: #800080"&gt;$mkey</span> = self::KEY_PREFIX.<span style="color: #800080"&gt;$lock_id</span><span style="color: #000000"&gt;;
    </span><span style="color: #800080"&gt;$ret</span> = <span style="color: #800080"&gt;$this</span>->mc->get(<span style="color: #800080"&gt;$mkey</span><span style="color: #000000"&gt;);
    </span><span style="color: #0000ff"&gt;if</span>(<span style="color: #0000ff"&gt;empty</span>(<span style="color: #800080"&gt;$ret</span>) || <span style="color: #800080"&gt;$ret</span> === <span style="color: #0000ff"&gt;false</span><span style="color: #000000"&gt;){
        </span><span style="color: #0000ff"&gt;return</span> <span style="color: #0000ff"&gt;false</span><span style="color: #000000"&gt;;
    }
    </span><span style="color: #0000ff"&gt;return</span> <span style="color: #0000ff"&gt;true</span><span style="color: #000000"&gt;;
}

</span><span style="color: #008000"&gt;/*</span><span style="color: #008000"&gt;*
 * 解锁
 * @param  [type] $lock_id
 * @return [type]
 </span><span style="color: #008000"&gt;*/</span>
<span style="color: #0000ff"&gt;public</span> <span style="color: #0000ff"&gt;function</span> unLock(<span style="color: #800080"&gt;$lock_id</span><span style="color: #000000"&gt;){
    </span><span style="color: #800080"&gt;$mkey</span> = self::KEY_PREFIX.<span style="color: #800080"&gt;$lock_id</span><span style="color: #000000"&gt;;
    </span><span style="color: #800080"&gt;$ret</span> = <span style="color: #800080"&gt;$this</span>->mc->delete(<span style="color: #800080"&gt;$mkey</span><span style="color: #000000"&gt;);
    </span><span style="color: #0000ff"&gt;return</span> <span style="color: #800080"&gt;$ret</span><span style="color: #000000"&gt;;
}
}

然后使用cacheLock进行并发热点代码控制
 =  = ->Lock('cachelock'(! "cachelock is lock" </span><span style="color: #008000"&gt;/*</span><span style="color: #008000"&gt;  热点代码 写在这里
  </span><span style="color: #008000"&gt;*/</span>

 <span style="color: #800080"&gt;$lockobj</span>->unLock('cachelock'<span style="color: #000000"&gt;);
}
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