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mysql-MMM主主复制
MMM（Master-Master replication manager for MySQL）是一套支持双主故障切换和双主日常管理的脚本程序,主要管理双主复制，而实际上在应用中只有一个主负责写的操作，另一台待机冗余，或者负责读的一部分操作。还可以结合主从复制，分离读写请求。
mmm分为agent端和monitor端，agent端部署在数据库节点上，monitor部署在监控管理端。monitor在整个数据库集群中是唯一存在的单点故障的点，因为monitor端只复制监控和管理agent节点，任务量非常的轻，一般不会出现什么故障的，而且monitor端在为agent数据库云服务器分配完vip地址后，即使停止了monitor服务，也不会影响业务的，只需要及时的修复即可。实在不放心可以为monitor部署keepalived.
环境
| 主机名： | 系统： | IP地址： | 安装软件： | 数据库角色 |
| m1 | centos6.5 | 192.168.100.150 | mysql mysql-server mysql-mmm* | master |
| m2 | centos6.5 | 192.168.100.151 | mysql mysql-server mysql-mmm* | master |
| m3 | centos6.5 | 192.168.100.152 | mysql mysql-server mysql-mmm* | slave |
| m4 | centos6.5 | 192.168.100.153 | mysql mysql-server mysql-mmm* | slave |
| monitor | centos6.5 | 192.168.100.154 | mysql mysql-mmm* | monitor监控 |
数据库角色，和对应vip：
| 主机： | vip | 角色 |
|
| m1 | 192.168.100.250
| write | 负责写的操作 |
| m2 | write | 平时不工作，待机冗余 |
| m3 | 192.168.100.201 | read | 读的操作 |
| m4 | 192.168.100.202 | read | 读的操作 |
修改主机名：依次修改m1 m2 m3 m4 monitor
分别在m1 - m4 安装mysql服务：
[root@m1 ~]# yum -y install mysql mysql-server mysql-devel
[root@m2 ~]# yum -y install mysql mysql-server mysql-devel
[root@m3 ~]# yum -y install mysql mysql-server mysql-devel
[root@m4 ~]# yum -y install mysql mysql-server mysql-devel
修改m1的mysql主配置文件：
[root@m1 ~]# vi /etc/my.cnf
[mysqld]
datadir=/var/lib/mysql
socket=/var/lib/mysql/mysql.sock
log-error=/var/lib/mysql/mysql.err
slow_query_log_file=/var/lib/mysql/slow_query_log.log
user=mysql
character-set-server=utf8
log-bin=mysql-bin
server-id=150
binlog-ignore-db=mysql,information_schema
log-slave-updates
sync_binlog=1
auto_increment_increment=2
auto_increment_offset=1
[client]
default_character_set=utf8
[mysqld_safe]
log-error=/var/log/mysqld.log
pid-file=/var/run/mysqld/mysqld.pid
启动mysql服务，查看是否启动
[root@m1 ~]# /etc/init.d/mysqld start
[root@m1 ~]# netstat -utpln |grep 3306tcp 0 0 0.0.0.0:3306 0.0.0.0:* LISTEN 1359/mysqld
将mysql的主配置文件同步到m2、m3、m4服务器上
[root@m1 ~]# for i in 1 2 3;do scp /etc/my.cnf root@192.168.100.15$i:/etc/;done
The authenticity of host '192.168.100.151 (192.168.100.151)' can't be established.
RSA key fingerprint is 6b:3d:8b:50:dc:45:ea:58:38:6e:5d:0d:9b:8f:04:f2.
Are you sure you want to continue connecting (yes/no)? yes
Warning: Permanently added '192.168.100.151' (RSA) to the list of known hosts.
root@192.168.100.151's password:
my.cnf 100% 465 0.5KB/s 00:00
The authenticity of host '192.168.100.152 (192.168.100.152)' can't be established.
RSA key fingerprint is 6b:3d:8b:50:dc:45:ea:58:38:6e:5d:0d:9b:8f:04:f2.
Are you sure you want to continue connecting (yes/no)? yes
Warning: Permanently added '192.168.100.152' (RSA) to the list of known hosts.
root@192.168.100.152's password:
my.cnf 100% 465 0.5KB/s 00:00
The authenticity of host '192.168.100.153 (192.168.100.153)' can't be established.
RSA key fingerprint is 6b:3d:8b:50:dc:45:ea:58:38:6e:5d:0d:9b:8f:04:f2.
Are you sure you want to continue connecting (yes/no)? yes
Warning: Permanently added '192.168.100.153' (RSA) to the list of known hosts.
root@192.168.100.153's password:
my.cnf 100% 465 0.5KB/s 00:00
登陆数据库查看该数据库的bin-log文件名和偏移量：
记下File Position的信息，等会要在m1-m2-m3数据库上用到。
[root@m1 ~]# mysqladmin -uroot password 123123
[root@m1 ~]# mysql -uroot -p123123
mysql> show master status;
+------------------+----------+--------------+--------------------------+
| File | Position | Binlog_Do_DB | Binlog_Ignore_DB |
+------------------+----------+--------------+--------------------------+
| mysql-bin.000003 | 249 | | mysql,information_schema |
+------------------+----------+--------------+--------------------------+
1 row in set (0.00 sec)
授权允许复制
mysql> grant replication slave on *.* to 'replication'@'192.168.100.%' identified by '123123';
Query OK, 0 rows affected (0.02 sec)
##授权replication用户在192.168.100.0这个网段有对数据库复制的权限
mysql> flush privileges; ##刷新权限
Query OK, 0 rows affected (0.00 sec)
mysql> quit
Bye
更改m2数据库配置文件
这是m1服务器同步过来的配置文件，只需将server-id改了就可以了，server-id在mysql集群中是唯一的标识符，在这里以ip地址结尾定义了
[root@m2 ~]# sed -i '/server-id/s/150/151/g' /etc/my.cnf
[root@m2 ~]# grep id /etc/my.cnf
server-id=151
pid-file=/var/run/mysqld/mysqld.pid
启动登入数据库
[root@m2 ~]# /etc/init.d/mysqld start
[root@m2 ~]# mysqladmin -uroot password 123123
[root@m2 ~]# mysql -uroot -p123123
在m2上查看bin-log文件和偏移量记录下来，并授权用户复制权限
mysql> show master status;
+------------------+----------+--------------+--------------------------+
| File | Position | Binlog_Do_DB | Binlog_Ignore_DB |
+------------------+----------+--------------+--------------------------+
| mysql-bin.000003 | 249 | | mysql,information_schema |
+------------------+----------+--------------+--------------------------+
1 row in set (0.00 sec)
mysql> grant replication slave on *.* to 'replication'@'192.168.100.%' identified by '123123';
Query OK, 0 rows affected (0.01 sec)
mysql> flush privileges;
Query OK, 0 rows affected (0.05 sec)
在m1上添加另一个主m2 同步数据
[root@m1 ~]# mysql -uroot -p123123
mysql> change master to
-> master_host='192.168.100.151', ##m2的ip
-> master_user='replication', ##m2上面授权的用户
-> master_password='123123', ##m2上授权用户的密码
-> master_log_file='mysql-bin.000003', ##m2的bin-log文件（刚刚在m2上查到的）
-> master_log_pos=249; ##日志文件的偏移量
Query OK, 0 rows affected (0.08 sec)
指定完了以后启动同步
mysql> start slave;
Query OK, 0 rows affected (0.00 sec)
查看同步状态信息：
这两项都为yes算是成功了
Slave_IO_Running: Yes
Slave_SQL_Running: Yes
mysql> show slave status\G;
*************************** 1. row ***************************
Slave_IO_State: Waiting for master to send event
Master_Host: 192.168.100.151
Master_User: replication
Master_Port: 3306
Connect_Retry: 60
Master_Log_File: mysql-bin.000003
Read_Master_Log_Pos: 495
Relay_Log_File: mysqld-relay-bin.000002
Relay_Log_Pos: 497
Relay_Master_Log_File: mysql-bin.000003
Slave_IO_Running: Yes
Slave_SQL_Running: Yes
Replicate_Do_DB:
Replicate_Ignore_DB:
Replicate_Do_Table:
Replicate_Ignore_Table:
Replicate_Wild_Do_Table:
Replicate_Wild_Ignore_Table:
Last_Errno: 0
Last_Error:
Skip_Counter: 0
Exec_Master_Log_Pos: 495
Relay_Log_Space: 653
Until_Condition: None
Until_Log_File:
Until_Log_Pos: 0
Master_SSL_Allowed: No
Master_SSL_CA_File:
Master_SSL_CA_Path:
Master_SSL_Cert:
Master_SSL_Cipher:
Master_SSL_Key:
Seconds_Behind_Master: 0
Master_SSL_Verify_Server_Cert: No
Last_IO_Errno: 0
Last_IO_Error:
Last_SQL_Errno: 0
Last_SQL_Error:
1 row in set (0.00 sec)
ERROR:
No query specified
在m2上添加m2的另一个主m1：
mysql> change master to
-> master_host='192.168.100.150',
-> master_user='replication',
-> master_password='123123',
-> master_log_file='mysql-bin.000003',
-> master_log_pos=249;
Query OK, 0 rows affected (0.10 sec)
mysql> start slave;
Query OK, 0 rows affected (0.00 sec)
mysql> show slave status\G;
*************************** 1. row ***************************
Slave_IO_State: Waiting for master to send event
Master_Host: 192.168.100.150
Master_User: replication
Master_Port: 3306
Connect_Retry: 60
Master_Log_File: mysql-bin.000003
Read_Master_Log_Pos: 741
Relay_Log_File: mysqld-relay-bin.000002
Relay_Log_Pos: 497
Relay_Master_Log_File: mysql-bin.000003
Slave_IO_Running: Yes
Slave_SQL_Running: Yes
Replicate_Do_DB:
Replicate_Ignore_DB:
Replicate_Do_Table:
Replicate_Ignore_Table:
Replicate_Wild_Do_Table:
Replicate_Wild_Ignore_Table:
Last_Errno: 0
Last_Error:
Skip_Counter: 0
Exec_Master_Log_Pos: 741
Relay_Log_Space: 653
Until_Condition: None
Until_Log_File:
Until_Log_Pos: 0
Master_SSL_Allowed: No
Master_SSL_CA_File:
Master_SSL_CA_Path:
Master_SSL_Cert:
Master_SSL_Cipher:
Master_SSL_Key:
Seconds_Behind_Master: 0
Master_SSL_Verify_Server_Cert: No
Last_IO_Errno: 0
Last_IO_Error:
Last_SQL_Errno: 0
Last_SQL_Error:
1 row in set (0.00 sec)
ERROR:
No query specified
验证：
在m1和m2上各创建个库验证是否同步：
m1上创建
mysql> create database m1_test;
Query OK, 1 row affected (0.01 sec)
mysql> show databases;
+--------------------+
| Database |
+--------------------+
| information_schema |
| m1_test |
| mysql |
| test |
| |
+--------------------+
5 rows in set (0.00 sec)
m2上查看
mysql> show databases;
+--------------------+
| Database |
+--------------------+
| information_schema |
| m1_test |
| mysql |
| test |
+--------------------+
4 rows in set (0.07 sec)
m2上新建库
mysql> create database test_m2;
Query OK, 1 row affected (0.04 sec)
m1上查看
mysql> show databases;
+--------------------+
| Database |
+--------------------+
| information_schema |
| m1_test |
| mysql |
| test |
| test_m2 |
+--------------------+
5 rows in set (0.00 sec)
正常同步了。
在m3-m4从数据库上指定主的数据库
[root@m3 ~]# sed -i '/server-id/s/150/152/g' /etc/my.cnf
[root@m3 ~]# grep id /etc/my.cnf
server-id=152
pid-file=/var/run/mysqld/mysqld.pid
[root@m3 ~]# /etc/init.d/mysqld start
[root@m3 ~]# mysqladmin -uroot password 123123
[root@m3 ~]# mysql -uroot -p123123
mysql> change master to
-> master_host='192.168.100.150',
-> master_user='replication',
-> master_password='123123',
-> master_log_file='mysql-bin.000003',
-> master_log_pos=249;
Query OK, 0 rows affected (0.08 sec)
mysql> start slave;
Query OK, 0 rows affected (0.00 sec)
mysql> show slave status\G;
*************************** 1. row ***************************
Slave_IO_State: Waiting for master to send event
Master_Host: 192.168.100.150
Master_User: replication
Master_Port: 3306
Connect_Retry: 60
Master_Log_File: mysql-bin.000003
Read_Master_Log_Pos: 929
Relay_Log_File: mysqld-relay-bin.000002
Relay_Log_Pos: 931
Relay_Master_Log_File: mysql-bin.000003
Slave_IO_Running: Yes
Slave_SQL_Running: Yes
Replicate_Do_DB:
Replicate_Ignore_DB:
Replicate_Do_Table:
Replicate_Ignore_Table:
Replicate_Wild_Do_Table:
Replicate_Wild_Ignore_Table:
Last_Errno: 0
Last_Error:
Skip_Counter: 0
Exec_Master_Log_Pos: 929
Relay_Log_Space: 1087
Until_Condition: None
Until_Log_File:
Until_Log_Pos: 0
Master_SSL_Allowed: No
Master_SSL_CA_File:
Master_SSL_CA_Path:
Master_SSL_Cert:
Master_SSL_Cipher:
Master_SSL_Key:
Seconds_Behind_Master: 0
Master_SSL_Verify_Server_Cert: No
Last_IO_Errno: 0
Last_IO_Error:
Last_SQL_Errno: 0
Last_SQL_Error:
1 row in set (0.04 sec)
ERROR:
No query specified
mysql> show databases
-> ;
+--------------------+
| Database |
+--------------------+
| information_schema |
| m1_test |
| mysql |
| test |
| test_m2 |
+--------------------+
5 rows in set (0.08 sec)
mysql>
[root@m4 ~]# sed -i '/server-id/s/150/153/g' /etc/my.cnf
[root@m4 ~]# grep id /etc/my.cnf
server-id=153
pid-file=/var/run/mysqld/mysqld.pid
[root@m4 ~]# /etc/init.d/mysqld start
[root@m4 ~]# mysqladmin -uroot password 123123
[root@m4 ~]# mysql -uroot -p123123
mysql> change master to
-> master_host='192.168.100.150',
-> master_user='replication',
-> master_password='123123',
-> master_log_file='mysql-bin.000003',
-> master_log_pos=249;
Query OK, 0 rows affected (0.10 sec)
mysql> start slave;
Query OK, 0 rows affected (0.00 sec)
mysql> show slave status\G;
*************************** 1. row ***************************
Slave_IO_State: Waiting for master to send event
Master_Host: 192.168.100.150
Master_User: replication
Master_Port: 3306
Connect_Retry: 60
Master_Log_File: mysql-bin.000003
Read_Master_Log_Pos: 929
Relay_Log_File: mysqld-relay-bin.000002
Relay_Log_Pos: 931
Relay_Master_Log_File: mysql-bin.000003
Slave_IO_Running: Yes
Slave_SQL_Running: Yes
Replicate_Do_DB:
Replicate_Ignore_DB:
Replicate_Do_Table:
Replicate_Ignore_Table:
Replicate_Wild_Do_Table:
Replicate_Wild_Ignore_Table:
Last_Errno: 0
Last_Error:
Skip_Counter: 0
Exec_Master_Log_Pos: 929
Relay_Log_Space: 1087
Until_Condition: None
Until_Log_File:
Until_Log_Pos: 0
Master_SSL_Allowed: No
Master_SSL_CA_File:
Master_SSL_CA_Path:
Master_SSL_Cert:
Master_SSL_Cipher:
Master_SSL_Key:
Seconds_Behind_Master: 0
Master_SSL_Verify_Server_Cert: No
Last_IO_Errno: 0
Last_IO_Error:
Last_SQL_Errno: 0
Last_SQL_Error:
1 row in set (0.00 sec)
ERROR:
No query specified
mysql> show databases;
+--------------------+
| Database |
+--------------------+
| information_schema |
| m1_test |
| mysql |
| test |
| test_m2 |
+--------------------+
5 rows in set (0.00 sec)
安装mysql-mmm:
下载epel扩展yum源： 在所用服务器上执行
wget -O /etc/yum.repos.d/epel.repo http://mirrors.aliyun.com/repo/epel-6.repo
安装mmm软件： 在所有服务器上执行
yum -y install mysql-mmm*
授权： 在m1上授权，其他主机会自动同步权限
[root@m1 ~]# mysql -uroot -p123123
mysql> grant replication client on *.* to 'mmm_monitor'@'192.168.100.%' identified by 'monitor';
Query OK, 0 rows affected (0.02 sec)
mysql> grant super,replication client,process on *.* to 'mmm_agent'@'192.168.100.&' identified by 'agent';
Query OK, 0 rows affected (0.00 sec)
mysql> flush privileges;
Query OK, 0 rows affected (0.00 sec)
修改配置文件： mmm_common.conf（所有节点的通用配置文件）
[root@monitor ~]# vi /etc/mysql-mmm/mmm_common.conf
active_master_role writer
cluster_interface eth0
pid_path /var/run/mysql-mmm/mmm_agentd.pid
bin_path /usr/libexec/mysql-mmm/
replication_user replication ##复制同步的用户名
replication_password 123123 ##同步的密码
agent_user mmm_agent ##代理的用户名
agent_password agent ##代理密码
ip 192.168.100.150
mode master
peer db2
ip 192.168.100.151
mode master
peer db1
ip 192.168.100.152
mode slave
ip 192.168.100.153
mode slave
hosts db1, db2
ips 192.168.100.250 ##写的vip
mode exclusive ##独占模式
hosts db3, db4
ips 192.168.100.201, 192.168.100.202 ##读的vip
mode balanced ##平衡模式
同步配置文件到m1 m2 m3 m4 上：
[root@monitor ~]# for i in 150 151 152 153;do scp /etc/mysql-mmm/mmm_common.conf root@192.168.100.$i:/etc/mysql-mmm/;done
The authenticity of host '192.168.100.150 (192.168.100.150)' can't be established.
RSA key fingerprint is 6b:3d:8b:50:dc:45:ea:58:38:6e:5d:0d:9b:8f:04:f2.
Are you sure you want to continue connecting (yes/no)? yes
Warning: Permanently added '192.168.100.150' (RSA) to the list of known hosts.
root@192.168.100.150's password:
mmm_common.conf 100% 851 0.8KB/s 00:00
The authenticity of host '192.168.100.151 (192.168.100.151)' can't be established.
RSA key fingerprint is 6b:3d:8b:50:dc:45:ea:58:38:6e:5d:0d:9b:8f:04:f2.
Are you sure you want to continue connecting (yes/no)? yes
Warning: Permanently added '192.168.100.151' (RSA) to the list of known hosts.
root@192.168.100.151's password:
mmm_common.conf 100% 851 0.8KB/s 00:00
The authenticity of host '192.168.100.152 (192.168.100.152)' can't be established.
RSA key fingerprint is 6b:3d:8b:50:dc:45:ea:58:38:6e:5d:0d:9b:8f:04:f2.
Are you sure you want to continue connecting (yes/no)? yes
Warning: Permanently added '192.168.100.152' (RSA) to the list of known hosts.
root@192.168.100.152's password:
mmm_common.conf 100% 851 0.8KB/s 00:00
The authenticity of host '192.168.100.153 (192.168.100.153)' can't be established.
RSA key fingerprint is 6b:3d:8b:50:dc:45:ea:58:38:6e:5d:0d:9b:8f:04:f2.
Are you sure you want to continue connecting (yes/no)? yes
Warning: Permanently added '192.168.100.153' (RSA) to the list of known hosts.
root@192.168.100.153's password:
mmm_common.conf 100% 851 0.8KB/s 00:00
修改数据库mysql-m1到mysql-m4：
[root@m1 ~]# vi /etc/mysql-mmm/mmm_agent.conf
[root@m1 ~]# cat /etc/mysql-mmm/mmm_agent.conf
include mmm_common.conf
this db1
[root@m2 ~]# vi /etc/mysql-mmm/mmm_agent.conf
[root@m2 ~]# cat /etc/mysql-mmm/mmm_agent.conf
include mmm_common.conf
this db2
[root@m3 ~]# vi /etc/mysql-mmm/mmm_agent.conf
[root@m3 ~]# cat /etc/mysql-mmm/mmm_agent.conf
include mmm_common.conf
this db3
[root@m4 ~]# vi /etc/mysql-mmm/mmm_agent.conf
[root@m4 ~]# cat /etc/mysql-mmm/mmm_agent.conf
include mmm_common.conf
this db4
[root@monitor ~]# vi /etc/mysql-mmm/mmm_mon.conf
[root@monitor ~]# cat /etc/mysql-mmm/mmm_mon.conf
include mmm_common.conf
ip 127.0.0.1
pid_path /var/run/mysql-mmm/mmm_mond.pid
bin_path /usr/libexec/mysql-mmm
status_path /var/lib/mysql-mmm/mmm_mond.status
ping_ips 192.168.100.150, 192.168.100.151, 192.168.100.152, 192.168.100.153
##监测每个节点数据库：修改为每个服务器的真实ip地址
auto_set_online 60 ##自动上线时间，
monitor_user mmm_monitor ##监控服务的用户名
monitor_password monitor ##监控服务的密码，这两项是在m1上授权的
debug 0
启动服务：m1-m4的mmm-agent服务; 监控端的mmm-monitor服务
[root@m1 ~]# /etc/init.d/mysql-mmm-agent start
Starting MMM Agent Daemon: [确定]
[root@m1 ~]#
[root@m2 ~]#
[root@m2 ~]# /etc/init.d/mysql-mmm-agent start
Starting MMM Agent Daemon: [确定]
[root@m3 ~]# /etc/init.d/mysql-mmm-agent start
Starting MMM Agent Daemon: [确定]
[root@m4 ~]# /etc/init.d/mysql-mmm-agent start
Starting MMM Agent Daemon: [确定]
[root@monitor ~]# /etc/init.d/mysql-mmm-monitor start
Starting MMM Monitor Daemon: [确定]
查看各代理数据库状态
[root@monitor ~]# mmm_control show
db1(192.168.100.150) master/ONLINE. Roles: writer(192.168.100.250)
db2(192.168.100.151) master/ONLINE. Roles:
db3(192.168.100.152) slave/ONLINE. Roles: reader(192.168.100.201)
db4(192.168.100.153) slave/ONLINE. Roles: reader(192.168.100.202)
##发现写的请求交给db1的vip，读的请求交给db3 db4 vip
使用vip登录数据库：
先在m1上授权：因为设置了同步，只在一个数据库上授权，其他数据库会同步权限
[root@m1 ~]# mysql -uroot -p123123 -s
mysql> grant all on *.* to 'root'@192.168.100.154 identified by '123123';
mysql> flush privileges;
[root@monitor ~]# mysql -uroot -p123123 -h 192.168.100.250 -s
mysql> show databases;
Database
information_schema
m1_test
mysql
test
test_m2
登陆读的数据库：
[root@monitor ~]# mysql -uroot -p123123 -h 192.168.100.201 -s
mysql> show databases;
Database
information_schema
m1_test
mysql
test
test_m2
mysql>
在生产环境中，只需在应用服务器上，指定写数据的vip地址，和读数据的vip地址池即可。
测试：
模拟主服务器m1故障,将mysql停止了,再查看状态：
[root@m1 ~]# /etc/init.d/mysqld stop
停止 mysqld： [确定]
[root@m1 ~]#
[root@monitor ~]# mmm_control show
db1(192.168.100.150) master/HARD_OFFLINE. Roles: ##显示为离线状态
db2(192.168.100.151) master/ONLINE. Roles: writer(192.168.100.250) ##vip转移到db2
db3(192.168.100.152) slave/ONLINE. Roles: reader(192.168.100.201)
db4(192.168.100.153) slave/ONLINE. Roles: reader(192.168.100.202)
再把m1启动
[root@m1 ~]# /etc/init.d/mysqld start
正在启动 mysqld： [确定]
[root@m1 ~]#
[root@monitor ~]# mmm_control show
db1(192.168.100.150) master/AWAITING_RECOVERY. Roles: ##恢复状态
db2(192.168.100.151) master/ONLINE. Roles: writer(192.168.100.250)
db3(192.168.100.152) slave/ONLINE. Roles: reader(192.168.100.201)
db4(192.168.100.153) slave/ONLINE. Roles: reader(192.168.100.202)
[root@monitor ~]# mmm_control show
db1(192.168.100.150) master/ONLINE. Roles: ##在线状态
db2(192.168.100.151) master/ONLINE. Roles: writer(192.168.100.250)
db3(192.168.100.152) slave/ONLINE. Roles: reader(192.168.100.201)
db4(192.168.100.153) slave/ONLINE. Roles: reader(192.168.100.202)
模拟从数据库m3故障，将数据库mysql停止查看状态，再启动查看状态
[root@m3 ~]# /etc/init.d/mysqld stop
停止 mysqld： [确定]
此时会将读数据库db3的vip转移到db4；db4暂时负责读的操作
[root@monitor ~]# mmm_control show
db1(192.168.100.150) master/ONLINE. Roles:
db2(192.168.100.151) master/ONLINE. Roles: writer(192.168.100.250)
db3(192.168.100.152) slave/HARD_OFFLINE. Roles:
db4(192.168.100.153) slave/ONLINE. Roles: reader(192.168.100.201), reader(192.168.100.202)
[root@m3 ~]# /etc/init.d/mysqld start
正在启动 mysqld： [确定]
[root@m3 ~]#
在db3数据库恢复正常后，vip会转移回来，从新工作接受读的操作
[root@monitor ~]# mmm_control show
db1(192.168.100.150) master/ONLINE. Roles:
db2(192.168.100.151) master/ONLINE. Roles: writer(192.168.100.250)
db3(192.168.100.152) slave/ONLINE. Roles: reader(192.168.100.201)
db4(192.168.100.153) slave/ONLINE. Roles: reader(192.168.100.202)
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