memcached主从复制
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Repcached介绍
Repchched项目地址:http://repcached.sourceforge.net/
关于repcached
“repcached”是一个补丁集合,它添加数据复制功能到memcached 1.2.x。
主要目的
实现冗余memcached系统。
主要功能多主复制。
异步数据复制。
支持所有的memcached命令(set, add, delete, incr/decr, flush_all, cas)。
Memcached 1.4.x的Repcached补丁
地址:http://mdounin.ru/
最新补丁:http://mdounin.ru/files/repcached-2.3.1-1.4.13.patch.gz
工作原理
repcached实现了memcached复制的功能,它是一个单master单slave的方案,但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,这时坏掉的master只能启用为slave,它们之间互换角色,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。
应用场景
用memcached做session共享或其它服务时会存在memcached的单点故障,如果memcached宕机,那么整个系统用户无法登陆(session)。
基于这种情况,采用repcached做memcached的主从冗余。
Repcached下载地址
http://sourceforge.net/projects/repcached/files/repcached/
Repcached安装方式
Repcached有两种安装方式:
1.补丁版本安装
先安装相应版本的memcached,然后对应版本的Repcached补丁。
2.整合版本安装
直接安装整合版本的memcached
方式一:补丁版本安装
1. 安装Memcache,相关安装方法可以参见博文:
http://ultrasql.blog.51cto.com/9591438/1632179
2. 下载对应的repcached版本补丁安装文件:
假设安装的memcahced版本为1.2.8,下载针对该版本最新的补丁:
wget http://softlayer-dal.dl.sourceforge.net/project/repcached/repcached/2.2.1-1.2.8/repcached-2.2.1-1.2.8.patch.gz
gzip -cd ../repcached-2.2.1-1.2.8.patch.gz | patch -p1
./configure --enable-replication
make && make install
方式二:整合版本安装
yum -y install gcc gcc-c++
安装libevent:
cd /tmp
wget http://downloads.sourceforge.net/levent/libevent-2.0.22-stable.tar.gz
tar zxvf libevent-2.0.22-stable.tar.gz
cd libevent-2.0.22-stable
./configure --prefix=/usr/
make && make install
将libevent的库文件添加到动态库中:
vi /etc/ld.so.conf
在最后添加如下行:
/usr/ //此处为要添加的libevent库目录
重新加载动态lib库
ldconfig
注意:如果无此步骤,在启动memcached时,会提示看不到libevent的库文件。
测试libevent是否安装成功:
ll /usr/lib/libevent*
3. 创建启动帐号:
groupadd memcached
useradd -g memcached memcached
4. 创建PID进程目录并修改所有者:
mkdir /var/run/memcached
chown -R memcached.memcached /var/run/memcached
5. 安装整合memcached-repcached包:
tar zxvf memcached-1.2.8-repcached-2.2.1.tar.gz
mv memcached-1.2.8-repcached-2.2.1 memcached
cd memcached
./configure --prefix=/usr/local/memcached --with-libevent=/usr/ --enable-replication --enable-64bit
注意:默认memcached单个进程只支持到2G内存,需要更大内存支持的话,需要打开64位支持,编译的时候加参数:
--enable-64bit
make && make install
提示编译出错:
make all-recursive
make[1]: Entering directory `/usr/local/memcached‘
Making all in doc
make[2]: Entering directory `/usr/local/memcached/doc‘
make[2]: Nothing to be done for `all‘.
make[2]: Leaving directory `/usr/local/memcached/doc‘
make[2]: Entering directory `/usr/local/memcached‘
gcc -DHAVE_CONFIG_H -I. -DNDEBUG -m64 -g -O2 -MT memcached-memcached.o -MD
MP -MF .deps/memcached-memcached.Tpo -c -o memcached-memcached.o `test -f
memcached.c‘ || echo ‘./‘`memcached.c
memcached.c: In function ‘add_iov’:
memcached.c:697: error: ‘IOV_MAX’ undeclared (first use in this function)
memcached.c:697: error: (Each undeclared identifier is reported only once
memcached.c:697: error: for each function it appears in.)
make[2]: *** [memcached-memcached.o] Error 1
make[2]: Leaving directory `/usr/local/memcached‘
make[1]: *** [all-recursive] Error 1
make[1]: Leaving directory `/usr/local/memcached‘
make: *** [all] Error 2
解决方案:
vi memcached.c
将下面的几行
/* FreeBSD 4.x doesn‘t have IOV_MAX exposed. */
#ifndef IOV_MAX
#if defined(__FreeBSD__) || defined(__APPLE__)
# define IOV_MAX 1024
#endif
#endif
修改为
/* FreeBSD 4.x doesn‘t have IOV_MAX exposed. */
#ifndef IOV_MAX
# define IOV_MAX 1024
#endif
重新编译和安装:
make && make install
修改memcached目录所有者:
cd ..
chown -R memcached.memcached memcached
配置主从复制
参数说明:
-x 设置从哪个IP上进行同步。
-X 指定数据同步的端口。
Memcached默认服务端口是11211,默认同步监听端口是11212。
启动Master:
/usr/local/memcached/bin/memcached -d -m 100 -l 192.168.11.51 -p 11211 -u memcached -c 1024 -x 192.168.11.52 -X 11212 -P /var/run/memcached/memcached-rep.pid
查看监听端口:
netstat -tupln | grep memcached
tcp 0 0 192.168.11.51:11211 0.0.0.0:* LISTEN 18634/memcached
tcp 0 0 192.168.11.51:11212 0.0.0.0:* LISTEN 18634/memcached
udp 0 0 192.168.11.51:11211 0.0.0.0:* 18634/memcached
启动Slave:
/usr/local/memcached/bin/memcached -d -m 100 -l 192.168.11.52 -p 11211 -u memcached -c 1024 -x 192.168.11.51 -X 11212 -P /var/run/memcached/memcached-rep.pid
说明:-x 192.168.11.51用于同步的Master的IP地址。
查看监听端口:
netstat -tupln | grep memcached
tcp 0 0 192.168.11.52:11211 0.0.0.0:* LISTEN 24262/memcached
udp 0 0 192.168.11.52:11211 0.0.0.0:* 24262/memcached
验证数据同步
在Master创建数据:
[[email protected] bin]# telnet 192.168.1.10 11211
Trying 192.168.1.10…
Connected to 192.168.1.10.
Escape character is ‘^]’.
get key1
END
set key1 0 0 2
aa
STORED
quit
Connection closed by foreign host.
在Slave获取数据:
[[email protected] bin]# telnet 192.168.1.11 11211
Trying 192.168.1.11…
Connected to 192.168.1.11.
Escape character is ‘^]’.
get key1
VALUE key1 0 2
aa
END
quit
Connection closed by foreign host.
在Slave创建数据:
[[email protected] bin]# telnet 192.168.1.11 11211
Trying 192.168.1.11…
Connected to 192.168.1.11.
Escape character is ‘^]’.
get key2
END
set key2 0 0 3
bbb
STORED
get key2
VALUE key2 0 3
bbb
END
quit
Connection closed by foreign host.
在Master获取数据:
[[email protected] bin]# telnet 192.168.1.10 11211
Trying 192.168.1.10…
Connected to 192.168.1.10.
Escape character is ‘^]’.
get key2
VALUE key2 0 3
bbb
END
quit
Connection closed by foreign host.
Memcached高可用
启动Master和Slave时不要加-l参数指定监听地址,否则keepalived无法监听VIP的地址。
然后配置上keepalived就可以作为高可用了。
以下是keppalived配置信息,在此就不多数了,相信大家都熟悉keepalived的作用了
MASTER 主机 配置信息
! Configuration File for keepalived
global_defs {
notification_email {
[email protected]
}
notification_email_from [email protected]
smtp_server 127.0.0.1
smtp_connect_timeout 30
router_id LVS_DEVEL
}
vrrp_instance VI_1 {
state MASTER
interface eth1
virtual_router_id 51
priority 101 主机 为 101
advert_int 1
authentication {
auth_type PASS 验证类型
auth_pass 1111 验证密码自己修改即可,记得主备机上的密码要一致
}
virtual_ipaddress {
192.168.1.120 虚拟IP 地址
}
}
SLAVE 从机 配置信息
! Configuration File for keepalived
global_defs {
notification_email {
[email protected]
}
notification_email_from [email protected]
smtp_server 127.0.0.1
smtp_connect_timeout 30
router_id LVS_DEVEL
}
vrrp_instance VI_1 {
state MASTER
interface eth1
virtual_router_id 51
priority 100 从机 为 100
advert_int 1
authentication {
auth_type PASS 验证类型
auth_pass 1111 验证密码自己修改即可,记得主备机上的密码要一致
}
virtual_ipaddress {
192.168.1.120 虚拟IP 地址
}
}
通过虚拟IP进行memcached 存取操作
[[email protected] happy]# telnet 192.168.1.120 11211
Trying 192.168.1.120…
Connected to 192.168.1.120.
Escape character is ‘^]’.
set key 0 0 6
123456
STORED
get key
VALUE key 0 6
123456
END
get key1
VALUE key1 0 2
aa
END
quit
Connection closed by foreign host.
OK keepalived + memcached主备模式到此设置完成了,下面我们来停止一台机器上的keepalived模拟down机,然后再用虚拟IP 192.168.1.120链接memcached并对其进行读写,看下能否正常访问到memcached数据就知道了主备模式是否健全了
[[email protected] happy]# telnet 192.168.1.120 11211
Trying 192.168.1.120…
Connected to 192.168.1.120.
Escape character is ‘^]’.
get key
VALUE key 0 6
123456
END
get key1
VALUE key1 0 2
aa
END
quit
Connection closed by foreign host.
OK MEMCACHED一切正常,不仅memcached实现了内存复制,而且keepalived运行也一切正常,至此一个完整可靠的memcached主备模式构建完成了。。。
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