db2(192.168.52.128) master/ONLINE. Roles: reader(192.168.52.129),writer(192.168.52.120)

db3(192.168.52.131) slave/ONLINE. Roles: reader(192.168.52.128),reader(192.168.52.131)

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[root@oraclem1 ~]#

Writer已经变成了db2了。

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（3）在monitor上查看后台日志，可以看到如下描述

[root@oraclem1 mysql-mmm]# tail -f /var/log/mysql-mmm/mmm_mond.log 

......

2015/04/14 01:34:11  WARN Check 'rep_backlog' on 'db1' is in unknown state! Message: UNKNOWN: Connect error (host = 192.168.52.129:3306, user = mmm_monitor)! Lost connection to MySQL server at 'reading initial communication packet', system error: 111

2015/04/14 01:34:11  WARN Check 'rep_threads' on 'db1' is in unknown state! Message: UNKNOWN: Connect error (host = 192.168.52.129:3306, user = mmm_monitor)! Lost connection to MySQL server at 'reading initial communication packet', system error: 111

2015/04/14 01:34:21 ERROR Check 'mysql' on 'db1' has failed for 10 seconds! Message: ERROR: Connect error (host = 192.168.52.129:3306, user = mmm_monitor)! Lost connection to MySQL server at 'reading initial communication packet', system error: 111

2015/04/14 01:34:23 FATAL State of host 'db1' changed from ONLINE to HARD_OFFLINE (ping: OK, mysql: not OK)

2015/04/14 01:34:23  INFO Removing all roles from host 'db1':

2015/04/14 01:34:23  INFO     Removed role 'reader(192.168.52.128)' from host 'db1'

2015/04/14 01:34:23  INFO     Removed role 'writer(192.168.52.120)' from host 'db1'

2015/04/14 01:34:23  INFO Orphaned role 'writer(192.168.52.120)' has been assigned to 'db2'

2015/04/14 01:34:23  INFO Orphaned role 'reader(192.168.52.128)' has been assigned to 'db3'

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9.3 停止db2，看writer自动切换到db1

（1）启动db1，并设置为online

[root@data01 ~]# service mysql start

Starting MySQL.................. SUCCESS!

[root@data01 ~]#

在monitor上设置db1为online

[root@oraclem1 ~]# mmm_control set_onlinedb1;

OK: State of 'db1' changed to ONLINE. Nowyou can wait some time and check its new roles!

[root@oraclem1 ~]#

在monitor上查看状态

[root@oraclem1 ~]# mmm_control show

db1(192.168.52.129) master/ONLINE. Roles: reader(192.168.52.131)

db2(192.168.52.128) master/ONLINE. Roles: reader(192.168.52.129),writer(192.168.52.120)

db3(192.168.52.131) slave/ONLINE. Roles: reader(192.168.52.128)

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[root@oraclem1 ~]#

OK，这里要启动db1，并且将db1设置成online，是因为mmm的配置里面master只能在db1和db2之间切换，在自动切换成功的情况下，必须保证要切换的对象master是online的，不然切换就会失败因为切换对象没有online。

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（2）停止db2

[root@data02 ~]# service mysql stop

Shutting down MySQL.. SUCCESS!

[root@data02 ~]#

（3）在monitor上查看master是否自动从db2切换到db1了

[root@oraclem1 ~]# mmm_control show

db1(192.168.52.129) master/ONLINE. Roles: reader(192.168.52.131),writer(192.168.52.120)

db2(192.168.52.128) master/HARD_OFFLINE. Roles:

db3(192.168.52.131)slave/ONLINE. Roles: reader(192.168.52.129), reader(192.168.52.128)

?

[root@oraclem1 ~]#

OK，writer已经自动变成db1了，db2处于HARD_OFFLINE状态，自动切换成功了。

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（4）去查看monitor后台日志

[root@oraclem1 mysql-mmm]# tail -f /var/log/mysql-mmm/mmm_mond.log

......

2015/04/14 01:56:13 ERROR Check 'mysql' on 'db2' has failed for 10 seconds! Message: ERROR: Connect error (host = 192.168.52.128:3306, user = mmm_monitor)! Lost connection to MySQL server at 'reading initial communication packet', system error: 111

2015/04/14 01:56:14 FATAL State of host 'db2' changed from ONLINE to HARD_OFFLINE (ping: OK, mysql: not OK)