主备环境切换

A.主从机器都正常运行的情况下切换

切换前:
主库：192.168.56.111
从库：192.168.56.112

切换后：
主库：192.168.56.112
从库：192.168.56.111

------------------------切换前的主库上的操作(192.168.56.111)-----------------------------------------------

1.停止主库，目的是停止生成新的业务数据
./mysqladmin -h localhost -u root -p -S /db/mysqlmha/data/mysql.sock shutdown

------------------------切换前的从库上的操作(192.168.56.112)-----------------------------------------------

1.查看从库日志是否已经应用完成
mysql> show slave status \G;
*************************** 1. row ***************************
               Slave_IO_State: Waiting for master to send event
                  Master_Host: 192.168.56.111
                  Master_User: repl
                  Master_Port: 3306
                Connect_Retry: 60
              Master_Log_File: binlog.000020
          Read_Master_Log_Pos: 82884208
               Relay_Log_File: slave-relay.000009
                Relay_Log_Pos: 51508938
        Relay_Master_Log_File: binlog.000020
             Slave_IO_Running: Yes
            Slave_SQL_Running: Yes
              Replicate_Do_DB:
          Replicate_Ignore_DB: information_schema,performance_schema
           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: 82884208
              Relay_Log_Space: 51509107
              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:
  Replicate_Ignore_Server_Ids:
             Master_Server_Id: 1
                  Master_UUID: 6455cec0-c03b-11e6-b85e-080027d12c51
             Master_Info_File: /db/mysqlmha/data/master.info
                    SQL_Delay: 0
          SQL_Remaining_Delay: NULL
      Slave_SQL_Running_State: Slave has read all relay log; waiting for the slave I/O thread to update it
           Master_Retry_Count: 86400
                  Master_Bind:
      Last_IO_Error_Timestamp:
     Last_SQL_Error_Timestamp:
               Master_SSL_Crl:
           Master_SSL_Crlpath:
           Retrieved_Gtid_Set:
            Executed_Gtid_Set:
                Auto_Position: 0
1 row in set (0.00 sec)

ERROR:
No query specified

2.停止从库同步io进程
mysql>stop slave io_thread

3.重置从库
mysql> stop slave;
mysql> reset master;
这个时候binlog日志文件重置,从binlog.000001开始

mysql> reset slave;
这个时候slave-relay日志重置,从slave-relay.000001开始

4.修改my.cnf配置文件
注释掉#read-only=1

5.重启从库
./mysqld_safe --defaults-file=/db/mysqlmha/conf/my.cnf --user=mysql
这个时候之前的从库就变成了主库

6.创建复制账号
mysql> grant replication slave ON *.* TO identified by 'mysql';
mysql> flush privileges; 

7.查找复制的文件和位置
mysql> show master status;
+---------------+----------+--------------+------------------+-------------------+
| File          | Position | Binlog_Do_DB | Binlog_Ignore_DB | Executed_Gtid_Set |
+---------------+----------+--------------+------------------+-------------------+
| binlog.000001 |      408 |              |                  |                   |
+---------------+----------+--------------+------------------+-------------------+
1 row in set (0.00 sec)

----------------切换前的主库上操作(192.168.56.111)--------------------------------------------------------
1.修改my.cnf文件,加上只读参数
read-only=1

2.启动之前的主库
./mysqld_safe --defaults-file=/db/mysqlmha/conf/my.cnf --user=mysql

3.重置
mysql> reset master;

4.配置复制
change master to master_host='192.168.56.112',
       master_port=3306,
       master_user='repl',
       master_password='mysql',
       master_log_file='binlog.000001',
       master_log_pos=408;

5.启动复制
mysql> start slave;

这样就完成了主从角色切换.

-- The End --