php memcached缓存集群php memcached
一、需求描述
一linode xen vps 1G RAM，40+sites，IO频繁，openfiles ulimit已65535
US时间访问量大增,nginx不定时502
二、解决办法
pages cache化,但这一台vps内存不够用，于是把闲置的几台服务器都装上memcached做缓存集群
再根据网络延迟设定权重
memcached server官方: http://memcached.org/
三、代码
访问memcached server需要php支持，可以选择memcached库和memcache库，注意2者名字的区别
详细对比：https:///p/memcached/wiki/PHPClientComparison
我采用的是php memcache: http://php.net/manual/en/book.memcache.php 因为memcache不依赖libmemcached
1 2 3 4 5 6 7 8 9 10 11
//集群数组$memserver = array(array( 'host' => 'fast1.xxx.com' , 'port' => 13579 , 'weight' => 40 ),array( 'host' => 'fast2.xxx.com' , 'port' => 13579 , 'weight' => 20 ),array( 'host' => 'fast3.xxx.com' , 'port' => 13579 , 'weight' => 20 ),array( 'host' => 'slow1.xxx.com' , 'port' => 24680 , 'weight' => 5 ),array( 'host' => 'slow2.xxx.com' , 'port' => 24680 , 'weight' => 5 ),array( 'host' => '' , 'port' => 11211 , 'weight' => 10 ));
键值读、写、删就没什么说的了直接按文档sample写即可
考虑到以后的移植问题，记得首先检测环境是否支持memcache: class_exists(‘Memcache’)
下面是我的实现，因为特定需求，几个函数写的相对独立，memcache也没做全局实例化。
你可以根据自己需求把memcache在全局实例化，优化操作。
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48
//---get content from memcache---function getCache( $key ){Global $memserver;$ret = false;$key = md5( $key );$mc = new Memcache();foreach ( $memserver as $s )$mc->addServer( $s['host'], $s['port'], FALSE, $s['weight'] );$ret = $mc->get( $key );$mc->close();unset( $mc );return $ret;}//---set content from memcache---function setCache( $key, $val ){Global $memserver;$ret = false;$key = md5( $key );$mc = new Memcache();foreach ( $memserver as $s )$mc->addServer( $s['host'], $s['port'], FALSE, $s['weight'] );if( isset($val['cached']) ){$val['cached'] = 1;$ret = $mc->set( $key , $val);}$mc->close();unset( $mc );return $ret;}//---delete content from memcache---function delCache( $key ){Global $memserver;$ret = false;$key = md5( $key );$mc = new Memcache();foreach ( $memserver as $s )$mc->addServer( $s['host'], $s['port'], FALSE, $s['weight'] );$ret = $mc->delete( $key , 0);$mc->close();unset( $mc );return $ret;}