PHP中的持久memcached-服务器池一直增长到curr_connections 10

Question

php prettyprint-override">class Cache {

    protected $memcached;

    public function __construct($cache_name) {
        $instance_name = 'persistent-' . $cache_name;
        $this->memcached = new Memcached($instance_name);
        $server_count = count($this->memcached->getServerList());
        echo '[MC] Server count of ', $instance_name, ': ', $server_count, PHP_EOL;

        if (0 == $server_count) {
            $servers = array(array("localhost","16586"),array("localhost","16587"));
            echo '[MC] Adding servers: ', json_encode($servers), PHP_EOL;
            // options don't change anything in my case
            $this->memcached->setOptions(array(
                Memcached::OPT_DISTRIBUTION => Memcached::DISTRIBUTION_CONSISTENT,
                Memcached::OPT_LIBKETAMA_COMPATIBLE => true
            ));
            $this->memcached->addServers($servers);
        }

        $stats = $this->memcached->getStats();
        foreach($stats as $server => $data){
            echo '[MC] Stats of ', $server, ' curr_connections: ', $data['curr_connections'], ' total_connections: ', $data['total_connections'], PHP_EOL;
        }
    }

    public function get($key) {
        echo '[MC] Server for key: ', $key, ' is ', json_encode($this->memcached->getServerByKey($key)), PHP_EOL;
        $ret = $this->memcached->get($key);
        echo '[MC] Getting ', $key, ' with result: ', $ret, PHP_EOL;
        return $ret;
    }

    public function set($key, $data, $timeout = 0) {
        echo '[MC] Set of ', $key, ' with data: ', $data, PHP_EOL;
        return $this->memcached->set($key, $data, $timeout);
    }
}

$cache = new Cache('instance');

$ret = $cache->get('something');

if(empty($ret)) {
    $cache->set('something', true);
}

我期望从这段代码中得到的是在建立连接后运行单个addservers。

新鲜运行（在memcached/apache重新启动之后）显示：

// first run
[MC] Server count of persistent-instance: 0
[MC] Adding servers: [["localhost","16586"],["localhost","16587"]]
[MC] Stats of localhost:16586 curr_connections: 5 total_connections: 6
[MC] Stats of localhost:16587 curr_connections: 5 total_connections: 6
[MC] Server for key: something is {"host":"localhost","port":16587,"weight":1}
[MC] Getting something with result: 
[MC] Set of something with data: 1

// second
[MC] Server count of persistent-instance: 0
[MC] Adding servers: [["localhost","16586"],["localhost","16587"]]
[MC] Stats of localhost:16586 curr_connections: 6 total_connections: 7
[MC] Stats of localhost:16587 curr_connections: 6 total_connections: 7
[MC] Server for key: something is {"host":"localhost","port":16587,"weight":1}
[MC] Getting something with result: 1

// up to 6th call curr_connections are growing and still adding servers to pool
[MC] Server count of persistent-instance: 0
[MC] Adding servers: [["localhost","16586"],["localhost","16587"]]
[MC] Stats of localhost:16586 curr_connections: 10 total_connections: 11
[MC] Stats of localhost:16587 curr_connections: 10 total_connections: 11
[MC] Server for key: something is {"host":"localhost","port":16587,"weight":1}
[MC] Getting something with result: 1

// 7th+ call finally with expected result
[MC] Server count of persistent-instance: 2
[MC] Stats of localhost:16586 curr_connections: 10 total_connections: 11
[MC] Stats of localhost:16587 curr_connections: 10 total_connections: 11
[MC] Server for key: something is {"host":"localhost","port":16587,"weight":1}
[MC] Getting something with result: 1

我是不是漏掉了什么？出什么事了？

null

此问题在我的最新配置中仍然存在：

• Xubuntu 13.10（内核3.11.0-19)
• Apache 2.4.6
• memcached 1.4.14
• libmemcached 1.0.8
• PHP 5.5.3-1Ubuntu2.3
• PHP 2.1.0的memcached库

Answer 1

我不知道你的“问题”是什么。您的每个Apache PHP“服务器”（即子服务器）在启动时还没有连接到memcache--因此每个服务器都需要初始化连接--它们都需要...一次。

现在每个工作者都有一个服务器列表。

如果您要查询它第二次-您将“看到”服务器列表…但您有一个缓存对象,我假设您只实例化一次。所以你永远不会再调用它，所以它永远不会再尝试调用getServers...所以您永远不会看到“这里是服务器列表”。

我说对了吗？

如果是这样，那就是关于“单身人士”的常见问题/误解之一。关于单身，你总是需要问的最重要的问题是“他们有多少”--因为他们只是在自己控制的上下文中“单身”....但在这种情况下，其他外部因素可能会造成更多的影响。在本例中，每个PHP实例有一个....但是您的apache创建了多个PHP实例--因此每个实例都有一个--并且这些实例不共享任何东西，因此每个实例都需要自己的全局、自己的到数据库的持久连接、到memcache的持久连接等等。

很高兴被纠正。