一，为什么要使用memcached
最优秀的cache软件，有效减轻数据库服务器的压力
不用它还要用哪个？

二，下载
从何处下载？

http://www.danga.com/memcached/

libevent从何处下载?

http://rpmforge.net/user/packages/libevent/

客户端php的memcache模块(python，java等需要哪个可以自行下载)下载，这里为PHP客户端为实例：

http://pecl.php.net/package/memcache/download/

三,如何进行安装libevent?

首先就是先下下载rpm包:

wget http://apt.sw.be/redhat/el4/en/i386/RPMS.dag/libevent-1.1a-1.2.el4.rf.i386.rpm

wget http://apt.sw.be/redhat/el4/en/i386/RPMS.dag/libevent-devel-1.1a-1.2.el4.rf.i386.rpm

rpm -ivh libevent-1.1a-1.2.el4.rf.i386.rpm

rpm -ivh libevent-devel-1.1a-1.2.el4.rf.i386.rpm

四，检查libevent安装是否成功？
[root@datam libevent-1.3e]# ls -al /usr/lib | grep libevent
lrwxrwxrwx 1 root root 22 Oct 6 00:20 libevent-1.1a.so.1 -> libevent-1.1a.so.1.0.2
-rwxr-xr-x 1 root root 31596 Jan 7 2007 libevent-1.1a.so.1.0.2
lrwxrwxrwx 1 root root 22 Oct 6 00:36 libevent-1.3e.so.1 -> libevent-1.3e.so.1.0.3
-rwxr-xr-x 1 root root 338439 Oct 6 00:36 libevent-1.3e.so.1.0.3
-rw-r–r– 1 root root 533978 Oct 6 00:36 libevent.a
-rwxr-xr-x 1 root root 828 Oct 6 00:36 libevent.la
lrwxrwxrwx 1 root root 22 Oct 6 00:36 libevent.so -> libevent-1.3e.so.1.0.3

五，安装memcached
tar -zxvf memcached-1.2.2.tar.gz
安装memcached时，需要指定libevent的安装位置：
./configure –prefix=/usr/local/memcache

# make
# make install
六，检查memcached安装是否成功？
1看文件
[root@datam memcached-1.2.2]# ls -al /usr/local/memcache/bin/mem*
-rwxr-xr-x 1 root root 141771 Oct 6 00:41 /usr/local/memcache/bin/memcached
-rwxr-xr-x 1 root root 151317 Oct 6 00:41 /usr/local/memcache/bin/memcached-debug

2，测试运行
[root@datam memcached-1.2.2]# /usr/local/bin/memcached -h
/usr/local/bin/memcached: error while loading shared libraries: libevent-1.3e.so.1: cannot open shared object file: No such file or directory
出错了，怎么办？
进行检查
[root@datam memcached-1.2.2]# LD_DEBUG=libs memcached -v
4962: find library=libevent-1.3e.so.1 [0]; searching
4962: search cache=/etc/ld.so.cache
4962: search path=/lib64/tls/x86_64:/lib64/tls:/lib64/x86_64:/lib64:/usr/lib64/tls/x86_64:/usr/lib64/tls:/usr/lib64/x86_64:/usr/lib64 (system search path)
4962: trying file=/lib64/tls/x86_64/libevent-1.3e.so.1
4962: trying file=/lib64/tls/libevent-1.3e.so.1
4962: trying file=/lib64/x86_64/libevent-1.3e.so.1
4962: trying file=/lib64/libevent-1.3e.so.1
4962: trying file=/usr/lib64/tls/x86_64/libevent-1.3e.so.1
4962: trying file=/usr/lib64/tls/libevent-1.3e.so.1
4962: trying file=/usr/lib64/x86_64/libevent-1.3e.so.1
4962: trying file=/usr/lib64/libevent-1.3e.so.1
4962:
memcached: error while loading shared libraries: libevent-1.3e.so.1: cannot open shared object file: No such file or directory
进行处理：
[root@datam memcached-1.2.2]# ln -s /usr/lib/libevent-1.3e.so.1 /usr/lib64/libevent-1.3e.so.1
[root@datam memcached-1.2.2]# memcached -h
memcached 1.2.2
-p <num> TCP port number to listen on (default: 11211)
-U <num> UDP port number to listen on (default: 0, off)
-s <file> unix socket path to listen on (disables network support)
-l <ip_addr> interface to listen on, default is INDRR_ANY
-d run as a daemon
-r maximize core file limit
-u <username> assume identity of <username> (only when run as root)
-m <num> max memory to use for items in megabytes, default is 64 MB
-M return error on memory exhausted (rather than removing items)
-c <num> max simultaneous connections, default is 1024
-k lock down all paged memory
-v verbose (print errors/warnings while in event loop)
-vv very verbose (also print client commands/reponses)
-h print this help and exit
-i print memcached and libevent license
-b run a managed instanced (mnemonic: buckets)
-P <file> save PID in <file>, only used with -d option
-f <factor> chunk size growth factor, default 1.25
-n <bytes> minimum space allocated for key+value+flags, default 48

至此安装完毕

七，如何启动memcached的服务端?
下面，我们来启动一个Memcached的服务器端：
# /usr/local/memcache/bin/memcached -d -m 10 -u root -l 192.168.0.200 -p 12000 -c 256 -P /tmp/memcached.pid
/usr/local/bin/memcached -d -m 128 -l localhost -p 11211 -u root
-d 以守护程序（daemon）方式运行 memcached；
-m 设置 memcached 可以使用的内存大小，单位为 M；
-l 设置监听的 IP 地址，如果是本机的话，通常可以不设置此参数；
-p 设置监听的端口，默认为 11211，所以也可以不设置此参数；
-u 指定用户;
-t <num> number of threads to use, default 4
如果有此项，说明已经支持了线程，就可以在启动的时候使用 -t 选项来启动多线程

然后启动的时候必须加上你需要支持的线程数量：
/usr/local/memcache/bin/memcached -t 1024
[root@datam memcached-1.2.2]# /usr/local/bin/memcached -d -m 128 -l localhost -p 11211 -u root
Illegal address: localhost

[root@datam memcached-1.2.2]# /usr/local/memcache/bin/memcached -d -m 128 -l 127.0.0.1 -p 11211 -u root
[root@datam memcached-1.2.2]#

至此启动成功

八,memcached的相关知识？
如何停止？如何重启？如何刷新其内容？等等
使用这个文件来实现：
#! /bin/sh
#
# chkconfig: - 55 45
# description: The memcached daemon is a network memory cache service.
# processname: memcached
# config: /etc/sysconfig/memcached

# Source function library.
. /etc/rc.d/init.d/functions

PORT1=11211
USER=nobody
MAXCONN=1024
CACHESIZE=64
OPTIONS=”-t 8″
MEMDAEMON=/usr/local/memcache/bin/memcached

if [ -f /etc/sysconfig/memcached ];then
. /etc/sysconfig/memcached
fi

# Check that networking is up.
if [ "$NETWORKING" = "no" ]
then
exit 0
fi

RETVAL=0
prog=”memcached”

start () {
echo -n $”Starting $prog: ”
# insure that /var/run/memcached has proper permissions
# chown $USER /var/run/memcached
daemon $MEMDAEMON -d -p $PORT1 -u $USER -m $CACHESIZE -c $MAXCONN $OPTIONS
RETVAL=$?
echo
[ $RETVAL -eq 0 ] && touch /var/lock/subsys/memcached
}
stop () {
echo -n $”Stopping $prog: ”
killproc memcached
RETVAL=$?
echo
if [ $RETVAL -eq 0 ] ; then
rm -f /var/lock/subsys/memcached
rm -f /var/run/memcached.pid
fi
}

restart () {
stop
start
}

# See how we were called.
case “$1″ in
start)
start
;;
stop)
stop
;;
status)
status memcached
;;
restart|reload)
restart
;;
condrestart)
[ -f /var/lock/subsys/memcached ] && restart || :
;;
*)
echo $”Usage: $0 {start|stop|status|restart|reload|condrestart}”
exit 1
esac

exit $?

九：配置php能访问memcached
wget http://pecl.php.net/get/memcache-2.2.0.tgz
tar -zxvf memcache-2.2.0.tgz
[root@datam memcache-2.2.0]# /usr/local/bin/phpize
Configuring for:
PHP Api Version: 20041225
Zend Module Api No: 20050922
Zend Extension Api No: 220051025
Cannot find autoconf. Please check your autoconf installation and the $PHP_AUTOCONF
environment variable is set correctly and then rerun this script.

没有autoconf
yum install autoconf
[root@datam memcache-2.2.0]# yum install autoconf
[root@datam memcache-2.2.0]# /usr/local/bin/phpize
Configuring for:
PHP Api Version: 20041225
Zend Module Api No: 20050922
Zend Extension Api No: 220051025

[root@datam memcache-2.2.0]# ./configure –enable-memcache –with-php-config=/usr/local/php/bin/php-config –with-zlib-dir

make
[root@datam memcache-2.2.0]# make install
Installing shared extensions: /usr/local/lib/php/extensions/no-debug-non-zts-20050922/

至此安装成功

下面我们需把此安装成功的模块添加到php中去
vi php.ini
add下面的这两行
extension_dir = “/usr/local/lib/php/extensions/no-debug-non-zts-20050922/”
extension=memcache.so
按照相应路径进行设置这个动态模块
然后重启apache
用phpinfo()看到存在以下信息，则表示模块安装成功

memcache

memcache support enabled
Active persistent connections 0
Revision $Revision: 1.86 $
Directive Local Value Master Value
memcache.allow_failover 1 1
memcache.chunk_size 8192 8192
memcache.default_port 11211 11211
memcache.hash_function crc32 crc32
memcache.hash_strategy standard standard
memcache.max_failover_attempts 20 20

十：编写php代码测试访问memcached

[ 接口介绍 ]
服 务器端和客户端都安装配置好了，现在我们就来测试以下我们的成果。Memcache客户端包含两组接口，一组是面向过程的接口，一组是面向对象的接口，具 体可以参考PHP手册 “LXXV. Memcache Functions” 这章。我们为了简单方便，就使用面向对象的方式，也便于维护和编写代码。Memcache面向对象的常用接口包括：

Memcache::connect — 打开一个到Memcache的连接
Memcache::pconnect — 打开一个到Memcache的长连接
Memcache::close — 关闭一个Memcache的连接
Memcache::set — 保存数据到Memcache服务器上
Memcache::get — 提取一个保存在Memcache服务器上的数据
Memcache::replace — 替换一个已经存在Memcache服务器上的项目（功能类似Memcache::set）
Memcache::delete — 从Memcache服务器上删除一个保存的项目
Memcache::flush — 刷新所有Memcache服务器上保存的项目（类似于删除所有的保存的项目）
Memcache::getStats — 获取当前Memcache服务器运行的状态

示例程序:

<?php
//连接
$mem = new Memcache;
$mem->connect(“127.0.0.1“, 11211);

//保存数据
$mem->set(‘key1‘, ‘This is first value‘, 0, 60);
$val = $mem->get(‘key1‘);
echo “Get key1 value: “ . $val .“<br>“;

//替换数据
$mem->replace(‘key1‘, ‘This is replace value‘, 0, 60);
$val = $mem->get(‘key1‘);
echo “Get key1 value: “ . $val . “<br>“;

//保存数组
$arr = array(‘aaa‘, ‘bbb‘, ‘ccc‘, ‘ddd‘);
$mem->set(‘key2‘, $arr, 0, 60);
$val2 = $mem->get(‘key2‘);
echo “Get key2 value: “;
print_r($val2);
echo “<br>“;

//删除数据
$mem->delete(‘key1‘);
$val = $mem->get(‘key1‘);
echo “Get key1 value: “ . $val . “<br>“;

//清除所有数据
$mem->flush();
$val2 = $mem->get(‘key2‘);
echo “Get key2 value: “;
print_r($val2);
echo “<br>“;

//关闭连接
$mem->close();
?>

如果正常的话，浏览器将输出：
Get key1 value: This is first value
Get key1 value: This is replace value
Get key2 value: Array ( [0] => aaa [1] => bbb [2] => ccc [3] => ddd )
Get key1 value:
Get key2 value:

十一:测试memcached缓存数据库的查询结果

<?php
/*
测试memcache缓存mysql的查询结果
by hd
2007.10.06
*/
//定义访问数据库的常量
define(SERVER_DATA_HOST,"127.0.0.1");
define(SERVER_DATA_USER,"root");
define(SERVER_DATA_PASS,"");
define(SERVER_DATA_BASE,"liuyan");

//定义访问数据库的常量
define(SERVER_MEM_HOST,”127.0.0.1″);
define(SERVER_MEM_PORT,”11211″);

//建立到数据库的连接
$dblink=mysql_connect(SERVER_DATA_HOST,SERVER_DATA_USER,SERVER_DATA_PASS);
mysql_select_db(SERVER_DATA_BASE,$dblink);

//定义到缓存的链接
$memlink = memcache_connect(SERVER_MEM_HOST,SERVER_MEM_PORT);

//定义访问数据库的函数
function sqlres($sqlstr)
{
global $dblink;
global $memlink;
$memstr = md5($sqlstr);
$memres = array();
if(!$memlink->get($memstr))
{
$dbres = mysql_query($sqlstr,$dblink);
$arrdata=array();
while ($dbrow = mysql_fetch_assoc($dbres))
{
$arrdata[]=$dbrow;
}

$memlink->set($memstr,$arrdata);

}
else
{
$memres = $memlink->get($memstr);

}
return $memres;
}

$sqlstr=”select * from rank”;
$arrdata=sqlres($sqlstr);
print_r($arrdata);
?>

十一:需要注意的问题

十一：封装一个访问memcached的类供调用