本文实例讲述了Memcached缓存系统的介绍、安装以及应用方法。分享给大家供大家参考，具体如下：
一. memcached 是什么?
memcached is a high-performance, distributed memory object caching system, generic in nature, but intended for use in speeding up dynamic web applications by alleviating database load.
memcached是一个高性能的、分布式内存对象缓存系统，应用广泛。 通过缓存数据库查询结果，减少数据库访问次数，以提高动态Web应用的速度、 提高可扩展性。
它可以应对任意多个连接，使用非阻塞的网络IO。由于它的工作机制是在内存中开辟一块空间，然后建立一个HashTable，Memcached自管理这些HashTable。还使用内置的内存块分配和哈希表算法，确保虚拟内存不会过来捣乱。
Memcached 官方网站：http://www.danga.com/memcached
二. memcached 的安装：
注：memcached 用到了libevent这个库用于Socket的处理，所以还需要安装libevent.官网：http://www.monkey.org/~provos/libevent/
1. 先安装libevent：
[root@localhost software]# tar zxvf libevent-1.4.11-stable.tar.gz[root@localhost libevent-1.4.11-stable]# ./configure –prefix=/usr[root@localhost libevent-1.4.11-stable]# make[root@localhost libevent-1.4.11-stable]# make install
2. 测试libevent是否安装成功
[root@localhost libevent-1.4.11-stable]# ls -al /usr/lib | grep libeventlrwxrwxrwx 1 root root 22 07-10 13:10 libevent-1.1a.so.1 -> libevent-1.1a.so.1.0.2-rwxr-xr-x 1 root root 31596 2007-01-07 libevent-1.1a.so.1.0.2lrwxrwxrwx 1 root root 21 07-21 03:33 libevent-1.4.so.2 -> libevent-1.4.so.2.1.3-rwxr-xr-x 1 root root 308088 07-21 03:33 libevent-1.4.so.2.1.3-rw-r--r-- 1 root root 394474 07-21 03:33 libevent.alrwxrwxrwx 1 root root 26 07-21 03:33 libevent_core-1.4.so.2 -> libevent_core-1.4.so.2.1.3-rwxr-xr-x 1 root root 109490 07-21 03:33 libevent_core-1.4.so.2.1.3-rw-r--r-- 1 root root 148742 07-21 03:33 libevent_core.a-rwxr-xr-x 1 root root 866 07-21 03:33 libevent_core.lalrwxrwxrwx 1 root root 26 07-21 03:33 libevent_core.so -> libevent_core-1.4.so.2.1.3lrwxrwxrwx 1 root root 27 07-21 03:33 libevent_extra-1.4.so.2 -> libevent_extra-1.4.so.2.1.3-rwxr-xr-x 1 root root 246870 07-21 03:33 libevent_extra-1.4.so.2.1.3-rw-r--r-- 1 root root 307370 07-21 03:33 libevent_extra.a-rwxr-xr-x 1 root root 873 07-21 03:33 libevent_extra.lalrwxrwxrwx 1 root root 27 07-21 03:33 libevent_extra.so -> libevent_extra-1.4.so.2.1.3-rwxr-xr-x 1 root root 831 07-21 03:33 libevent.lalrwxrwxrwx 1 root root 21 07-21 03:33 libevent.so -> libevent-1.4.so.2.1.3
安装OK。
3. 安装memcached，同时需要安装中指定libevent的安装位置
[root@localhost software]# tar zxvf memcached-1.4.0.tar.gz[root@localhost memcached-1.4.0]# ./configure –with-libevent=/usr[root@localhost memcached-1.4.0]# make[root@localhost memcached-1.4.0]# make intall
4. 测试是否成功安装memcached
[root@localhost memcached-1.4.0]# ls -al /usr/local/bin | grep memcached-rwxr-xr-x 1 root root 188225 07-21 03:35 memcached
安装OK。
三. 如何启动 memcached 服务：
只需要启动一个 memcached 监护进程，监护进程不需要配置文件，只要在命令行里面加三四个参数就可以了:
-d： (run as a daemon) 选项是启动一个守护进程
-m：(max memory to use for items in megabytes (default: 64 MB))是分配给Memcache使用的内存数量，单位是MB，我这里是100MB，
-u：(assume identity of <username> (only when run as root))是运行Memcache的用户，我这里是root，
-l：(interface to listen on)是监听的服务器IP地址，如果有多个地址的话，这里指定了服务器的IP地址127.0.0.1，
-p：是设置Memcache监听的端口，这里设置了11211，最好是1024以上的端口，
-c：选项是最大运行的并发连接数，默认是1024，这里设置了256，根据服务器的负载量来设定，
-P：(save PID in <file>, only used with -d option)是设置保存Memcache的pid文件，这里是保存在 /tmp/memcached.pid
注：也可以启动多个守护进程，不过端口不能重复。
四. 安装 Memcached 的PHP扩展：
在PHP中使用Memcached，有两种方式：
一种是安装PHP的memcached扩展。该扩展是用c写的，效率较高，需要在服务器上安装。
另外一种则是直接使用客户端的php-memcached-client类库。
下面是使用PECL中Memcache的专用扩展，因为毕竟是用C写的，效率高，而且安装部署起来也比较方便。
1. 在 http://pecl.php.net/package/memcache 选择相应想要下载的memcache版本。我下载的是:memcache-2.2.5.tgz 版本。
2. 安装 memcache
[root@localhost software]# tar zxvf memcache-2.2.5.tgz[root@localhost software]# cd memcache-2.2.5[root@localhost memcache-2.2.5]# /usr/bin/phpize[root@localhost memcache-2.2.5]# ./configure –enable-memcache –with-php-config=/usr/bin/php-config –with-zlib-dir[root@localhost memcache-2.2.5]# make[root@localhost memcache-2.2.5]# make install
这步会有类似这样的提示：Installing shared extensions: /usr/local/php/modules
3. 把/etc/php.ini中的
extension_dir = "./"
修改为：
extension_dir = "/usr/lib/php/modules"
4. 并添加： extension=memcache.so
也可执行以下shell命令，对php.ini文件的修改：
五. 安装C/C++ Memcached客户端库：libmemcached
下载：http://download.tangent.org/libmemcached-0.32.tar.gz
1. 安装 libmemcached
[root@localhost src]# tar zxvf libmemcached-0.32.tar.gz[root@localhost src]# cd libmemcached-0.32[root@localhost libmemcached-0.32]# ./configure --prefix=/usr[root@localhost libmemcached-0.32]# make && make install
2. 检查安装结果
[root@localhost src]# ls /usr/lib/libmemcache* //库文件[root@localhost src]# ls /usr/include/libmemcached/* //头文件[root@localhost src]# ls /usr/bin/mem* //命令行工具
六. 应用：
1. 启动 memcache 服务
2. 重启 Web 服务器
[root@localhost bin]# service httpd restart
3. 创建 demo 测试程序
<?php//连接$mem = new Memcache;$mem->connect("127.0.0.1", 11211);echo 'Memcache Version is:'.$mem->getVersion().'<br/>';//保存数据$mem->set('key1', 'This is first memcache demo', 0, 60);$val = $mem->get('key1');echo "Get key1 value: ".$val."<br/>"//关闭连接$mem->close();?>4. Memcached客户端与tokyotyrant DB操作访问
<?php$memcache = new memcache();$memcache->addServer('127.0.0.1:1978');function microtime_float(){ list($usec, $sec) = explode(" ", microtime()); return ((float)$usec + (float)$sec);}$time_start = microtime_float();$data = 'abc123';for($i = 0;$i <= 20000 ;$i++){ $key = (string) rand(1,100); $memcache->set($key, $data);}for($i = 0;$i <= 20000 ;$i++){ $key = (string) rand(1,100); echo $data = $memcache->get($key).'-'.$i.'<br/>';}$time_end = microtime_float();$time = $time_end - $time_start;echo $time;$memcache->close();?>5. C/C++ 与 Memcached 结合代码
#include <stdio.h>#include <stdlib.h>#include <string.h>#include <libmemcached/memcached.h>int main(int argc, char *argv[]){ memcached_st *memc; memcached_return rc; memcached_server_st *servers; char value[8191]; //连接服务器 memc = memcached_create(NULL); servers = memcached_server_list_append(NULL, "127.0.0.1",11211, &rc); rc = memcached_server_push(memc, servers); memcached_server_free(servers); //存储数据 strcpy(value, "This is c first value"); rc = memcached_set(memc, "key1", 4, value, strlen(value), (time_t)180, (uint32_t)0); if (rc == MEMCACHED_SUCCESS) { printf("Save key:key1 data:/"%s/" success./n", value); } //获取数据 char return_key[MEMCACHED_MAX_KEY]; size_t return_key_length; char *return_value; size_t return_value_length; char *keys[]= {"key1"}; size_t key_length[]= {4}; uint32_t flags; rc = memcached_mget(memc, keys, key_length, 1); return_value = memcached_fetch(memc, return_key, &return_key_length, &return_value_length, &flags, &rc); if (rc == MEMCACHED_SUCCESS) { printf("Fetch key:%s data:%s/n", return_key, return_value); } //删除数据 rc = memcached_delete(memc, "key1", 4, (time_t)0); if (rc == MEMCACHED_SUCCESS) { printf("Delete Key key1 success./n"); } //释放内存 memcached_free(memc); return 0;}编译源代码：
[root@localhost html]# gcc -o cmem cmem.c -lmemcached[root@localhost html]# ./cmem //执行Save key:key1 data:"This is c first value" success.Fetch key:key1 data:This is c first valueDelete Key key1 success.
6. C/C++ 与 Memcached 分布式结合代码
#include <stdio.h>#include <stdlib.h>#include <string.h>#include <libmemcached/memcached.h>int main(int argc, char *argv[]){ memcached_st *memc; memcached_return rc; memcached_server_st *servers; char value[8191]; //connect multi server memc = memcached_create(NULL); servers = memcached_server_list_append(NULL, "localhost", 11211, &rc); servers = memcached_server_list_append(servers, "localhost", 11212, &rc); rc = memcached_server_push(memc, servers); memcached_server_free(servers); //Save multi data size_t i; char *keys[]= {"key1", "key2", "key3"}; size_t key_length[]= {4, 4, 4}; char *values[] = {"This is c first value", "This is c second value", "This is c third value"}; size_t val_length[]= {21, 22, 21}; for (i=0; i <3; i++) { rc = memcached_set(memc, keys[i], key_length[i], values[i], val_length[i], (time_t)180,(uint32_t)0); if (rc == MEMCACHED_SUCCESS) { printf("Save key:%s data:/"%s/" success./n", keys[i], values[i]); } } //Fetch multi data char return_key[MEMCACHED_MAX_KEY]; size_t return_key_length; char *return_value; size_t return_value_length; uint32_t flags; rc = memcached_mget(memc, keys, key_length, 3); while ((return_value = memcached_fetch(memc, return_key, &return_key_length, &return_value_length, &flags, &rc))) { if (rc == MEMCACHED_SUCCESS) { printf("Fetch key:%s data:%s/n", return_key, return_value); } } //Delete multi data for (i=0; i <3; i++) { rc = memcached_set(memc, keys[i], key_length[i], values[i], val_length[i], (time_t)180, (uint32_t)0); rc = memcached_delete(memc, keys[i], key_length[i], (time_t)0); if (rc == MEMCACHED_SUCCESS) { printf("Delete %s success/n", keys[i], values[i]); } } //free memcached_free(memc); return 0;}编译源代码：
[root@localhost html]# gcc -o cmultmem cmultmem.c -lmemcached[root@localhost html]# ./cmultmem //执行Save key:key1 data:"This is c first value" success.Save key:key2 data:"This is c second value" success.Save key:key3 data:"This is c third value" success.Fetch key:key2 data:This is c second valueFetch key:key3 data:This is c third valueFetch key:key1 data:This is c first valueDelete key1 successDelete key2 successDelete key3 success
以上c/c++代码摘自：黑夜路人
7. 查看Memcache进程
[root@localhost html]# ps aux | grep memcachedroot 11382 0.0 0.7 55124 1896 ? Ssl 13:06 0:00 memcached -d -m 100 -u root -l 127.0.0.1 -p 11211 -c 256 -P /tmp/memcached.pidroot 11395 0.0 0.2 3912 664 pts/1 R+ 13:08 0:00 grep memcached
8. 结束Memcache进程
[root@localhost html]# kill `cat /tmp/memcached.pid`
希望本文所述对大家memcached缓存程序设计有所帮助。
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