Linux:Memcached无单点解决方案
July 10, 2015
Table of Contents
一．Repcached （memcached同步补丁）
下载地址：http://sourceforge.net/projects/repcached/files/repcached/2.2.1-1.2.8/
版本号：memcached 1.2.8 repcached 2.2.1
1、repcached介绍
repcached是日本人开发的实现memcached复制功能，它是一个单 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坏掉， 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
2、安装
在两台服务器上分别安装memcached服务，另注本文libevent的版本为：libevent-1.4.13，下载地址: http://www.monkey.org/~provos/libevent-1.4.13-stable.tar.gz （安装省略）
repcached有两种方式：
方式一、下载对应的repcached版本
#wget http://downloads.sourceforge.net/repcached/memcached-1.2.8-repcached-2.2.tar.gz #tar zxf memcached-1.2.8-repcached-2.2.tar.gz #cd memcached-1.2.8-repcached-2.2
方式二、下载对应patch版本
#wget http://downloads.sourceforge.net/repcached/repcached-2.2-1.2.8.patch.gz #gzip -cd ../repcached-2.2-1.2.8.patch.gz | patch -p1】 #./configure –enable-replication # make # make install
3、启动：
启动master
# ./memcached -v -u root -d -l 127.0.0.1 -p 11211 -x 127.0.0.1 -X 11111 （11211：master端口；11111：同步端口） replication: connect (peer=127.0.0.1:11111) replication: accept replication: marugoto copying replication: start
启动salve
# ./memcached -v -u root -d -l 127.0.0.1 -p 11212 -x 127.0.0.1 -X 11111 （11212：slave端口；11111：同步端口） replication: connect (peer=127.0.0.1:11111) replication: marugoto copying replication: close replication: listen
4、测试：
操作master
[root@localhost bin]# telnet 127.1 11211 Trying 127.0.0.1... Connected to localhost.localdomain (127.0.0.1)... Escape character is '^]'. get key1 END set key1 0 0 2 aa STORED quit Connection closed by foreign host.
查看slave
[root@localhost bin]# telnet 127.1 11212 Trying 127.0.0.1... Connected to localhost.localdomain (127.0.0.1)... Escape character is '^]'. get key1 VALUE key1 0 2 aa END quit Connection closed by foreign host.
注意：如果master down机，slave接管并成为master，这时down机的master只能启用slave,他们之间互换角色，才能保持复制功能。换句话说，master没有抢占功能。而且，同步间隔时间未知。
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
二．Magent （memcached的代理）
原文地址：http://blog.s135.com/post/393/
magent是一款开源的Memcached代理服务器软件，其项目网址为：
http://code.google.com/p/memagent/
1、安装步骤：
a、编译安装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 ../
b、编译安装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 ../
c、编译安装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 ../
2、使用实例：
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
- 分别在11211、11212、11213端口启动3个Memcached进程，在12000端口开启magent代理程序；
- 11211、11212端口为主Memcached，11213端口为备份Memcached；
- 连接上12000的magent，set key1和set key2，根据哈希算法，key1被写入11212和11213端口的Memcached，key2被写入11212和11213端口的Memcached；
- 当11211、11212端口的Memcached死掉，连接到12000端口的magent取数据，数据会从11213端口的Memcached取出；
- 当11211、11212端口的Memcached重启复活，连接到12000端口，magent会从11211或11212端口的Memcached取数据，由于这两台Memcached重启后无数据，因此magent取得的将是空值，尽管11213端口的Memcached还有数据（此问题尚待改进）。
3、整个测试流程：
[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.
模拟11211、11212端口的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.
模拟11211、11212端口的Memcached重启复活
[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.
优点：
- 可以做多主或多从
缺点：
- 当master宕掉又恢复后，取不到数据。
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