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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是一個高性能的、分布式內存對象緩存系統，應用廣泛。通過緩存數據庫查詢結果，減少數據庫訪問次數，以提高動態Web應用的速度、 提高可擴展性。
它可以應對任意多個連接，使用非阻塞的網絡IO。由于它的工作機制是在內存中開辟一塊空間，然后建立一個HashTable，Memcached自管理這些HashTable。還使用內置的內存塊分配和哈希表算法，確保虛擬內存不會過來搗亂。
Memcached 官方網站：http://www.danga.com/memcached

二. memcached 的安裝：
注：memcached 用到了libevent這個庫用于Socket的處理，所以還需要安裝libevent.官網：http://www.monkey.org/~provos/libevent/
1. 先安裝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. 測試libevent是否安裝成功
[root@localhost libevent-1.4.11-stable]# ls -al /usr/lib | grep libevent
lrwxrwxrwx?? 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.1.0.2
lrwxrwxrwx?? 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.a
lrwxrwxrwx?? 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.la
lrwxrwxrwx?? 1 root root?????? 26 07-21 03:33 libevent_core.so -> libevent_core-1.4.so.2.1.3
lrwxrwxrwx?? 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.la
lrwxrwxrwx?? 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.la
lrwxrwxrwx?? 1 root root?????? 21 07-21 03:33 libevent.so -> libevent-1.4.so.2.1.3

安裝OK。

3. 安裝memcached，同時需要安裝中指定libevent的安裝位置
[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. 測試是否成功安裝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

安裝OK。

三. 如何啟動 memcached 服務：
只需要啟動一個 memcached 監護進程，監護進程不需要配置文件，只要在命令行里面加三四個參數就可以了:
[root@localhost bin]# memcached -d -m 100 -u root -l 127.0.0.1 -p 11211 -c 256 -P /tmp/memcached.pid
-d： (run as a daemon) 選項是啟動一個守護進程
-m：(max memory to use for items in megabytes (default: 64 MB))是分配給Memcache使用的內存數量，單位是MB，我這里是100MB，
-u：(assume identity of <username> (only when run as root))是運行Memcache的用戶，我這里是root，
-l：(interface to listen on)是監聽的服務器IP地址，如果有多個地址的話，這里指定了服務器的IP地址127.0.0.1，
-p：是設置Memcache監聽的端口，這里設置了11211，最好是1024以上的端口，
-c：選項是最大運行的并發連接數，默認是1024，這里設置了256，根據服務器的負載量來設定，
-P：(save PID in <file>, only used with -d option)是設置保存Memcache的pid文件，這里是保存在 /tmp/memcached.pid

注：也可以啟動多個守護進程，不過端口不能重復。

四. 安裝 Memcached 的PHP擴展：
在PHP中使用Memcached，有兩種方式：
一種是安裝PHP的memcached擴展。該擴展是用c寫的，效率較高，需要在服務器上安裝。
另外一種則是直接使用客戶端的php-memcached-client類庫。
下面是使用PECL中Memcache的專用擴展，因為畢竟是用C寫的，效率高，而且安裝部署起來也比較方便。
1. 在 http://pecl.php.net/package/memcache 選擇相應想要下載的memcache版本。我下載的是:memcache-2.2.5.tgz 版本。
2. 安裝 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
這步會有類似這樣的提示：Installing shared extensions: /usr/local/php/modules
3. 把/etc/php.ini中的extension_dir = “./”修改為：extension_dir = "/usr/lib/php/modules"
4. 并添加： extension=memcache.so

也可執行以下shell命令，對php.ini文件的修改：
sed -i 's#extension_dir = "./"#extension_dir = "/usr/local/webserver/php/lib/php/extensions/no-debug-non-zts-20060613/"/nextension = "memcache.so"/n#' /usr/local/webserver/php/etc/php.ini

五. 安裝C/C++ Memcached客戶端庫：libmemcached
下載：http://download.tangent.org/libmemcached-0.32.tar.gz
1. 安裝 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. 檢查安裝結果
[root@localhost src]# ls /usr/lib/libmemcache* //庫文件
[root@localhost src]# ls /usr/include/libmemcached/* //頭文件
[root@localhost src]# ls /usr/bin/mem* //命令行工具

六. 應用：
1. 啟動 memcache 服務
[root@localhost bin]# memcached -d -m 100 -u root -l 127.0.0.1 -p 11211 -c 256 -P /tmp/memcached.pid
2. 重啟 Web 服務器
[root@localhost bin]# service httpd restart
3. 創建 demo 測試程序
<?php
//連接
$mem = new Memcache;
$mem->connect("127.0.0.1", 11211);

echo 'Memcache Version is:'.$mem->getVersion().'<br/>';

//保存數據
$mem->set('key1', 'This is first memcache demo', 0, 60);
$val = $mem->get('key1');
echo "Get key1 value: ".$val."<br/>"

//關閉連接
$mem->close();
?>

4. Memcached客戶端與tokyotyrant DB操作訪問
<?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++ 與 Memcached 結合代碼
#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];

??? //連接服務器
??? 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);

??? //存儲數據
??? 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);
??? }

??? //獲取數據
??? 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);
??? }

??? //刪除數據
??? rc = memcached_delete(memc, "key1", 4, (time_t)0);
??? if (rc == MEMCACHED_SUCCESS) {
??? printf("Delete Key key1 success./n");
??? }
???
??? //釋放內存
??? memcached_free(memc);
??? return 0;
}

編譯源代碼：
[root@localhost html]# gcc -o cmem cmem.c -lmemcached
[root@localhost html]# ./cmem //執行
Save key:key1 data:"This is c first value" success.
Fetch key:key1 data:This is c first value
Delete Key key1 success.

6. C/C++ 與 Memcached 分布式結合代碼
#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;
}
編譯源代碼：
[root@localhost html]# gcc -o cmultmem cmultmem.c -lmemcached
[root@localhost html]# ./cmultmem //執行
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 value
Fetch key:key3 data:This is c third value
Fetch key:key1 data:This is c first value
Delete key1 success
Delete key2 success
Delete key3 success
以上c/c++代碼摘自：黑夜路人

7. 查看Memcache進程
[root@localhost html]# ps aux | grep memcached
root???? 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.pid
root???? 11395? 0.0? 0.2?? 3912?? 664 pts/1??? R+?? 13:08?? 0:00 grep memcached

8. 結束Memcache進程
[root@localhost html]# kill `cat /tmp/memcached.pid`

For more：http://cn.php.net/memcache

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