Repcached说明
    Repcached是一个单master单 slave的方案，但它的 master/slave都是可读写的，而且可以相互同步。如果 master down掉， slave侦测到连接断了，它会自动 listen而成为 master；而如果 slave坏掉， master也会侦测到连接断，它就会重新 listen等待新的 slave加入。 

Repcached 安装：
1：安装条件（root用户执行）

apt-get install libevent-dev

wget http://downloads.sourceforge.net/repcached/memcached-1.2.8-repcached-2.2.tar.gz

2：解压&进入目录编译

root@m2:~/nosql# tar zxvf memcached-1.2.8-repcached-2.2.tar.gz

cd memcached-1.2.8-repcached-2.2/

./configure --enable-replication --program-transform-name=s/memcached/repcached/

make&&make install 

注意：make的时候报错

memcached.c: 在函数‘add_iov’中:
memcached.c:696:30: 错误： ‘IOV_MAX’未声明(在此函数内第一次使用)
memcached.c:696:30: 附注： 每个未声明的标识符在其出现的函数内只报告一次
make[2]: *** [memcached-memcached.o] 错误 1

需要修改 memcached.c 文件：

/* FreeBSD 4.x doesn't have IOV_MAX exposed. */
#ifndef IOV_MAX
#if defined(__FreeBSD__) || defined(__APPLE__)
# define IOV_MAX 1024
#endif
#endif 改成： /* FreeBSD 4.x doesn't have IOV_MAX exposed. */
#ifndef IOV_MAX
# define IOV_MAX 1024
#endif

再make&&make install，编译之后退出root用户。

开启repcached：

启动master：[必须是11211端口]

1：
zhoujy@m2:~$ repcached -d -m 64 -p 11211 -u nobody -l 127.0.0.1 -v
zhoujy@m2:~$ replication: listen
或则：
2：
zhoujy@m2:~$ repcached -d -m 64 -p 11211 -u nobody -l 127.0.0.1 -x 127.0.0.1 -X 11111 -v    #（11211：master端口；11111：同步端口）
zhoujy@m2:~$ replication: connect (peer=127.0.0.1:11111)
replication: marugoto copying
replication: close
replication: listen

启动slave： -x：同行memcached的地址。

1：
zhoujy@m2:~$ repcached -d -m 64 -p 11212 -u nobody -l 127.0.0.1 -x 127.0.0.1  -v
zhoujy@m2:~$ replication: connect (peer=127.0.0.1:11212)
replication: marugoto copying
或则：
2：
zhoujy@m2:~$ repcached -d -m 64 -p 11212 -u nobody -l 127.0.0.1 -x 127.0.0.1 -X 11111 -v   #（11212：slave端口；11111：同步端口）
zhoujy@m2:~$ replication: connect (peer=127.0.0.1:11111)
replication: marugoto copying
replication: accept
replication: start

复制：11211的数据复制到11212中

zhoujy@m2:~$ telnet 127.0.0.1 11211
Trying 127.0.0.1...
Connected to 127.0.0.1.
Escape character is '^]'.
set a 0 0 3
abc
STORED
set aa 0 0 5
abcde
STORED
quit
Connection closed by foreign host.

zhoujy@m2:~$ telnet 127.0.0.1 11212
Trying 127.0.0.1...
Connected to 127.0.0.1.
Escape character is '^]'.
get a
VALUE a 0 3
abc
END
get aa
VALUE aa 0 5
abcde
END

反复制：11212 同步到了11211

set b 0 0 3
ABC
STORED
set bb 0 0 5
ABCDE
STORED

quit
Connection closed by foreign host.
zhoujy@m2:~$ telnet 127.0.0.1 11211
Trying 127.0.0.1...
Connected to 127.0.0.1.
Escape character is '^]'.
get b
VALUE b 0 3
ABC
END
get bb
VALUE bb 0 5
ABCDE
END

主从相互删除等操作都相互影响：

zhoujy@m2:~$ telnet 127.0.0.1 11211
Trying 127.0.0.1...
Connected to 127.0.0.1.
Escape character is '^]'.
delete aa
DELETED
delete bb
DELETED
quit
Connection closed by foreign host.
zhoujy@m2:~$ telnet 127.0.0.1 11212
Trying 127.0.0.1...
Connected to 127.0.0.1.
Escape character is '^]'.
get aa
END
get bb
END
delete a
DELETED
get a
END
quit
Connection closed by foreign host.
zhoujy@m2:~$ telnet 127.0.0.1 11211
Trying 127.0.0.1...
Connected to 127.0.0.1.
Escape character is '^]'.
get a
END
get b
VALUE b 0 3
ABC
END

至此，上面的同步已经完成。

优点：
数据冗余
两台memcached都可以进行读写操作

缺点：
只支持单对单
只支持memcached 1.2.x版本

 
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