Memcached HA架构探索

https://code.google.com/p/memagent/

标签：memcached magent 高可用 HA 架构
原创作品，允许转载，转载时请务必以超链接形式标明文章原始出处、作者信息和本声明。否则将追究法律责任。http://centilinux.blog.51cto.com/1454781/968104

magent是一款开源的Memcached代理服务器软件，可以用它做一些高可用架构尝试。目前magent已更新到0.6，我在centos 6.0 64bit机器上面未编译通过，所以我在这里用0.5的源码来测试;

google项目地址：http://code.google.com/p/memagent/

一、安装步骤：
1、编译安装libevent：

wget https://github.com/downloads/lib ... .0.16-stable.tar.gz
tar zxvf libevent-2.0.16-stable.tar.gz
cd libevent-2.0.16-stable/
./configure --prefix=/usr
make && make install
cd ../

2、编译安装Memcached：

wget http://memcached.googlecode.com/files/memcached-1.4.14.tar.gz
tar zxvf memcached-1.4.14.tar.gz
cd memcached-1.4.14/
./configure --prefix=/usr --with-libevent=/usr
make && make install
cd ../

3、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
vim Makefile
CFLAGS = -Wall -O2 -g
改为：
CFLAGS = -lrt -Wall -O2 -g
sed -i "s#LIBS = -levent#LIBS = -levent -lm#g" Makefile
vim ketama.h
加入
#ifndef SSIZE_MAX
#define SSIZE_MAX 32767
#endif
make
cp magent /usr/bin/magent
cd ../

安装中常遇到的问题

gcc -lrt -Wall -g -O2 -I/usr/local/include -m64 -c -o magent.o magent.c
magent.c: In function ‘writev_list’:
magent.c:729: error: ‘SSIZE_MAX’ undeclared (first use in this function)
magent.c:729: error: (Each undeclared identifier is reported only once
magent.c:729: error: for each function it appears in.)
make: *** [magent.o] Error 1

解决办法：

vim ketama.h
加入
#ifndef SSIZE_MAX
#define SSIZE_MAX 32767
#endif

二、高可用网络架构
此架构生产环境需要负载均衡器做负载，具体使用什么软件或硬件就要看你的具体情况来定了。

生产环境每台服务器分别启动一个memcached进程和magen进程做冗余

memcached -d -m 256 -l 192.168.10.11 -p 11211 -u www -c 10240 -P /tmp/memcached.pid -vv >/home/logs/memcached.txt 2>&1
memcached -d -m 128 -l 192.168.10.12 -p 11211 -u www -c 10240 -P /tmp/memcached.pid -vv >/home/logs/memcached.txt 2>&1
memcached -d -m 128 -l 192.168.10.13 -p 11211 -u www -c 10240 -P /tmp/memcached.pid -vv >/home/logs/memcached.txt 2>&1
magent -u www -n 51200 -l 192.168.10.11 -p 12000 -s 192.168.10.12:11211 -s 192.168.10.13:11211 -b 192.168.10.11:11211
magent -u www -n 51200 -l 192.168.10.12 -p 12000 -s 192.168.10.12:11211 -s 192.168.10.13:11211 -b 192.168.10.11:11211
magent -u www -n 51200 -l 192.168.10.13 -p 12000 -s 192.168.10.12:11211 -s 192.168.10.13:11211 -b 192.168.10.11:11211

参数说明：
-s 为要写入的memcached，
-b 为备份用的memcached。
说明：测试环境用magent和memached的不同端口来实现，在生产环境中可以将magent和memached作为一组放到多台服务器上。
看到了吧这样的架构最好做负载了，用一个VIP分别映射三台magent的12000端口即可。
#实验环境测试过程：

[root@odb ~]# telnet 127.0.0.1 12000
Trying 127.0.0.1…
Connected to localhost.localdomain (127.0.0.1).
Escape character is ‘^]’.
set key 0 0 8 <—在10000端口设置key的值
88888888
STORED
quit
Connection closed by foreign hos
[root@odb ~]# telnet 127.0.0.1 11211
Trying 127.0.0.1…
Connected to localhost.localdomain (127.0.0.1).
Escape character is ‘^]’.
get key <—在11211端口获取key的值成功
VALUE key 0 8
88888888
END
quit
Connection closed by foreign host.
[root@odb ~]# telnet 127.0.0.1 11211
Trying 127.0.0.1…
Connected to localhost.localdomain (127.0.0.1).
Escape character is ‘^]’.
get key <—在11211端口获取key的值成功
VALUE key 0 8
88888888
END
quit
Connection closed by foreign host.
高可用性测试：
[root@odb ~]# ps aux |grep -v grep |grep memcached
root 23455 0.0 0.0 5012 1796 ? Ss 09:22 0:00 memcached -m 1 -u root -d -l 127.0.0.1 -p 11212
root 24950 0.0 0.0 4120 1800 ? Ss 10:58 0:00 memcached -m 1 -u root -d -l 127.0.0.1 -p 11211
[root@odb ~]# ps aux |grep -v grep |grep ‘magent -u’
root 25919 0.0 0.0 2176 484 ? Ss 12:00 0:00 magent -u root -n 51200 -l 127.0.0.1 -p 10000 -s 127.0.0.1:11211 -b 127.0.0.1:11212
root 25925 0.0 0.0 3004 484 ? Ss 12:00 0:00 magent -u root -n 51200 -l 127.0.0.1 -p 11000 -s 127.0.0.1:11212 -b 127.0.0.1:11211
[root@odb ~]# telnet 127.0.0.1 10000
Trying 127.0.0.1…
Connected to localhost.localdomain (127.0.0.1).
Escape character is ‘^]’.
set stone 0 0 6 <—在10000端口设置stone的值
123456
STORED
quit
Connection closed by foreign host.
[root@odb ~]# telnet 127.0.0.1 11000
Trying 127.0.0.1…
Connected to localhost.localdomain (127.0.0.1).
Escape character is ‘^]’.
set shidl 0 0 6 <—在11000端口设置shidl的值
666666
STORED
get stone <—在11000端口获取stone的值成功
VALUE stone 0 6
123456
END
incr stone 2 <—在11000端口修改stone的值成功
123458
get stone
VALUE stone 0 6 <—在11000端口验证stone的值，证明上面的修改成功
123458
END
get shidl <—在11000端口获取shidl的值成功
VALUE shidl 0 6
666666
END
quit <—退出11000端口
Connection closed by foreign host.
[root@odb ~]# telnet 127.0.0.1 10000
Trying 127.0.0.1…
Connected to localhost.localdomain (127.0.0.1).
Escape character is ‘^]’.
get stone <—在10000端口获取stone的值，已被修改
VALUE stone 0 6
123458
END
get shidl <—在10000端口获取shidl的值成功
VALUE shidl 0 6
666666
END
delete shidl <—在10000端口删除shidl
DELETED
get shidl <—在10000端口删除shidl生效
END
quit
Connection closed by foreign host.
[root@odb ~]# telnet 127.0.0.1 11000
Trying 127.0.0.1…
Connected to localhost.localdomain (127.0.0.1).
Escape character is ‘^]’.
get shidl <—在11000端口验证删除shidl生效
END
get stone <—在11000端口获取stone的值成功
VALUE stone 0 6
123458
END
quit
Connection closed by foreign host.

Down机模拟测试：
Down掉11211端口的memcached：

[root@odb ~]# kill -9 24950
[root@odb ~]# telnet 127.0.0.1 10000
Trying 127.0.0.1…
Connected to localhost.localdomain (127.0.0.1).
Escape character is ‘^]’.
get stone <—在10000依然可以获取stone的值
VALUE stone 0 6
123458
END
quit
Connection closed by foreign host.
[root@odb ~]# telnet 127.0.0.1 11000
Trying 127.0.0.1…
Connected to localhost.localdomain (127.0.0.1).
Escape character is ‘^]’.
get stone <—在11000依然可以获取stone的值
VALUE stone 0 6
123458
END
quit
Connection closed by foreign host.
Down掉11000端口的magent：
[root@odb ~]# kill -9 25925
[root@odb ~]# telnet 127.0.0.1 10000
Trying 127.0.0.1…
Connected to localhost.localdomain (127.0.0.1).
Escape character is ‘^]’.
get stone <—在10000依然可以获取stone的值
VALUE stone 0 6
123458
END
quit
Connection closed by foreign host.

本文出自 “Centi.Linux” 博客，请务必保留此出处http://centilinux.blog.51cto.com/1454781/968104