Memcached的Proxy 伺服器軟體：magent使用小記

　[文章作者：張宴 本文版本：v1.0 最後修改：2009.01.19 轉載請註明原文連結：http://blog.s135.com/post/393/

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　　magent是一款開源的MemcachedProxy 伺服器軟體，其項目網址為：

　　http://code.google.com/p/memagent/

　　一、安裝步驟：

　　1、編譯安裝libevent：

wget http://monkey.org/~provos/libevent-1.4.9-stable.tar.gz

tar zxvf libevent-1.4.9-stable.tar.gz

cd libevent-1.4.9-stable/

./configure --prefix=/usr

make && make install

cd ../

　　2、編譯安裝Memcached：

wget http://danga.com/memcached/dist/memcached-1.2.6.tar.gz

tar zxvf memcached-1.2.6.tar.gz

cd memcached-1.2.6/

./configure --with-libevent=/usr

make && make install

cd ../

　　3、編譯安裝magent：

mkdir magent

cd magent/

wget http://memagent.googlecode.com/files/magent-0.5.tar.gz

tar zxvf magent-0.5.tar.gz

/sbin/ldconfig

sed -i "s#LIBS = -levent#LIBS = -levent -lm#g" Makefile

make

cp magent /usr/bin/magent

cd ../

 

　　二、使用執行個體：

memcached -m 1 -u root -d -l 127.0.0.1 -p 11211

memcached -m 1 -u root -d -l 127.0.0.1 -p 11212

memcached -m 1 -u root -d -l 127.0.0.1 -p 11213

magent -u root -n 51200 -l 127.0.0.1 -p 12000 -s 127.0.0.1:11211 -s 127.0.0.1:11212 -b 127.0.0.1:11213

　　1、分別在11211、11212、11213連接埠啟動3個Memcached進程，在12000連接埠開啟magent代理程式；

　　2、11211、11212連接埠為主Memcached，11213連接埠為備份Memcached；

　　3、串連上12000的magent，set key1和set key2，根據雜湊演算法，key1被寫入11212和11213連接埠的Memcached，key2被寫入11212和11213連接埠的Memcached；

　　4、當11211、11212連接埠的Memcached死掉，串連到12000連接埠的magent取資料，資料會從11213連接埠的Memcached取出；

　
　5、當11211、11212連接埠的Memcached重啟複活，串連到12000連接埠，magent會從11211或11212連接埠的
Memcached取資料，由於這兩台Memcached重啟後無資料，因此magent取得的將是空值，儘管11213連接埠的Memcached還有數
據（此問題尚待改進）。

　　三、整個測試流程：

[root@centos52 ~]# telnet 127.0.0.1 12000

Trying 127.0.0.1...

Connected to 127.0.0.1.

Escape character is '^]'.
stats

memcached agent v0.4

matrix 1 -> 127.0.0.1:11211, pool size 0

matrix 2 -> 127.0.0.1:11212, pool size 0

END
set key1 0 0 8

zhangyan

STORED
set key2 0 0 8

zhangyan

STORED
quit

Connection closed by foreign host.

[root@centos52 ~]# telnet 127.0.0.1 11211

Trying 127.0.0.1...

Connected to 127.0.0.1.

Escape character is '^]'.
get key1

END
get key2

VALUE key2 0 8

zhangyan

END
quit

Connection closed by foreign host.

[root@centos52 ~]# telnet 127.0.0.1 11212

Trying 127.0.0.1...

Connected to 127.0.0.1.

Escape character is '^]'.
get key1

VALUE key1 0 8

zhangyan

END
get key2

END
quit

Connection closed by foreign host.

[root@centos52 ~]# telnet 127.0.0.1 11213

Trying 127.0.0.1...

Connected to 127.0.0.1.

Escape character is '^]'.
get key1

VALUE key1 0 8

zhangyan

END
get key2

VALUE key2 0 8

zhangyan

END
quit

Connection closed by foreign host.

類比11211、11212連接埠的Memcached死掉

[root@centos52 ~]# ps -ef | grep memcached

root      6589     1  0 01:25 ?        00:00:00 memcached -m 1 -u root -d -l 127.0.0.1 -p 11211

root      6591     1  0 01:25 ?        00:00:00 memcached -m 1 -u root -d -l 127.0.0.1 -p 11212

root      6593     1  0 01:25 ?        00:00:00 memcached -m 1 -u root -d -l 127.0.0.1 -p 11213

root      6609  6509  0 01:44 pts/0    00:00:00 grep memcached

[root@centos52 ~]# kill -9 6589

[root@centos52 ~]# kill -9 6591

[root@centos52 ~]# telnet 127.0.0.1 12000

Trying 127.0.0.1...

Connected to 127.0.0.1.

Escape character is '^]'.
get key1

VALUE key1 0 8

zhangyan

END
get key2

VALUE key2 0 8

zhangyan

END
quit

Connection closed by foreign host.

類比11211、11212連接埠的Memcached重啟複活

[root@centos52 ~]# memcached -m 1 -u root -d -l 127.0.0.1 -p 11211

[root@centos52 ~]# memcached -m 1 -u root -d -l 127.0.0.1 -p 11212

[root@centos52 ~]# telnet 127.0.0.1 12000

Trying 127.0.0.1...

Connected to 127.0.0.1.

Escape character is '^]'.
get key1

END
get key2

END
quit

Connection closed by foreign host.

 

附用法介紹
：

magent
is a simple but useful proxy program for memcached
servers.

It features:

• keeps connections to memcached servers
• supports following memcached commands
  1. get gets
  2. delete
  3. incr decr
  4. add set replace prepend append
  5. cas
• event-driven by using libevent
  library
• supports ketama algorithm
• backup servers farm
• unix domain socket

Usage:

  -h this message
  -u uid
  -g gid
  -p port, default is 11211. (0 to disable tcp support)
  -s ip:port, set memcached server ip and port
  -b ip:port, set backup memcached server ip and port
  -l ip, local bind ip address, default is 0.0.0.0
  -n number, set max connections, default is 4096
  -D do not go to background
  -k use ketama key allocation algorithm
  -f file, unix socket path to listen on. default is off
  -i number, max keep alive connections for one memcached server, default is 20
  -v verbose

Changelog:

2010/4/14: memcached agent 0.6

1. add connection keepalive handler
2. bug fix, more robust, more debug messages

Examples:

  magent -s 10.1.2.1 -s 10.1.2.2:11211 -b 10.1.2.3:14000 -v

Notes:

1. current magent's speed is about 80% of memcached's. finding way to speed it up(not good)
2. adding backup server does no harm to magent's performance. (good)
3. magent's cpu usage is less than memcached's and has very little memory usage. (good)