switchover
在主备机正常时，出于维护的需要，将备机切换为主机，可保证切换过程中数据不丢失。
查看集群实例主备状态：1节点为主库，2节点为备库
$ gs_om -t status --detail
[ Cluster State ]
cluster_state : Normal
redistributing : No
current_az : AZ_ALL
[ Datanode State ]
node node_ip instance state | node node_ip instance state
--------------------------------------------------------------------------------------------------------------------------------------------------------------------
1 cen7-og1-02 192.168.229.53 6001 /opt/MogDB/data/dn P Primary Normal | 2 cen7-og1-03 192.168.229.54 6002 /opt/MogDB/data/dn S Standby Normal
在备节点执行切换主备操作：
$ gs_ctl switchover -D /opt/MogDB/data/dn
[2021-01-15 02:44:55.125][1034][][gs_ctl]: gs_ctl switchover ,datadir is /opt/MogDB/data/dn
[2021-01-15 02:44:55.125][1034][][gs_ctl]: switchover term (1)
[2021-01-15 02:44:55.137][1034][][gs_ctl]: waiting for server to switchover…
[2021-01-15 02:45:06.250][1034][][gs_ctl]: done
[2021-01-15 02:45:06.250][1034][][gs_ctl]: switchover completed (/opt/MogDB/data/dn)
确认集群主备状态：1节点为备库，2节点为主库
$ gs_om -t status --detail
[ Cluster State ]
cluster_state : Normal
redistributing : No
current_az : AZ_ALL
[ Datanode State ]
node node_ip instance state | node node_ip instance state
--------------------------------------------------------------------------------------------------------------------------------------------------------------------
1 cen7-og1-02 192.168.229.53 6001 /opt/MogDB/data/dn P Standby Normal | 2 cen7-og1-03 192.168.229.54 6002 /opt/MogDB/data/dn S Primary Normal
保存数据库主备机器信息：确保gs_om -t refreshconf 命令执行成功，否则再次重启会影响数据库状态。
$ gs_om -t refreshconf
Generating dynamic configuration file for all nodes.
Successfully generated dynamic configuration file.
failover
测试1：在主机异常时，将备机切换为主机。
查看集群实例主备状态：1节点为备库，2节点为主库
$ gs_om -t status --detail
[ Cluster State ]
cluster_state : Normal
redistributing : No
current_az : AZ_ALL
[ Datanode State ]
node node_ip instance state | node node_ip instance state
--------------------------------------------------------------------------------------------------------------------------------------------------
1 og201.2.test 192.168.2.157 6001 /mogdata/db1 P Primary Normal | 2 og201.3.test 192.168.2.158 6002 /mogdata/db1 S Standby Normal
主节点关闭数据库，模拟主节点故障
$ gs_ctl stop -D /mogdata/db1
[2021-12-27 11:34:07.742][24807][][gs_ctl]: gs_ctl stopped ,datadir is /mogdata/db1
waiting for server to shut down......... done
server stopped
备节点执行主备切换操作：
$ gs_ctl failover -D /mogdata/db1
[2021-12-27 11:34:42.304][28315][][gs_ctl]: gs_ctl failover ,datadir is /mogdata/db1
[2021-12-27 11:34:42.304][28315][][gs_ctl]: failover term (1)
[2021-12-27 11:34:42.310][28315][][gs_ctl]: waiting for server to failover...
.[2021-12-27 11:34:43.327][28315][][gs_ctl]: done
[2021-12-27 11:34:43.327][28315][][gs_ctl]: failover completed (/mogdata/db1)
确认集群主备状态：备库切换为主库
$ gs_om -t status --detail
[ Cluster State ]
cluster_state : Degraded
redistributing : No
current_az : AZ_ALL
[ Datanode State ]
node node_ip instance state | node node_ip instance state
--------------------------------------------------------------------------------------------------------------------------------------------------
1 og201.2.test 192.168.2.157 6001 /mogdata/db1 P Down Manually stopped | 2 og201.3.test 192.168.2.158 6002 /mogdata/db1 S Primary Normal
在确定降为备机的节点以standy模式启动MogDB服务：
$$ gs_ctl start -D /mogdata/db1 -M standby
[2021-12-27 11:35:10.858][24918][][gs_ctl]: gs_ctl started,datadir is /mogdata/db1
[2021-12-27 11:35:11.010][24918][][gs_ctl]: waiting for server to start...
…
[2021-12-27 11:35:12.032][24918][][gs_ctl]: done
[2021-12-27 11:35:12.032][24918][][gs_ctl]: server started (/mogdata/db1)
确认集群状态：主备节点已顺利切换
$ gs_om -t status --detail
[ Cluster State ]
cluster_state : Normal
redistributing : No
current_az : AZ_ALL
[ Datanode State ]
node node_ip instance state | node node_ip instance state
--------------------------------------------------------------------------------------------------------------------------------------------------
1 og201.2.test 192.168.2.157 6001 /mogdata/db1 P Standby Normal | 2 og201.3.test 192.168.2.158 6002 /mogdata/db1 S Primary Normal
保存数据库主备机器信息：确保gs_om -t refreshconf 命令执行成功，否则再次重启会影响数据库状态。
$ gs_om -t refreshconf
Generating dynamic configuration file for all nodes.
Successfully generated dynamic configuration file.
测试2：在主机正常时，将备机切换为主机。
将主机重启为备机之后，备机将处于需要修复状态，需要对备机进行build操作。
$ gs_om -t status --detail
[ Cluster State ]
cluster_state : Normal
redistributing : No
current_az : AZ_ALL
[ Datanode State ]
node node_ip instance state | node node_ip instance state
--------------------------------------------------------------------------------------------------------------------------------------------------------------------
1 cen7-og1-02 192.168.229.53 6001 /opt/MogDB/data/dn P Standby Normal | 2 cen7-og1-03 192.168.229.54 6002 /opt/MogDB/data/dn S Primary Normal
备节点执行主备切换操作：
$ gs_ctl failover -D /opt/MogDB/data/dn
[2021-01-15 03:33:13.803][17292][][gs_ctl]: gs_ctl failover ,datadir is /opt/MogDB/data/dn
[2021-01-15 03:33:13.803][17292][][gs_ctl]: failover term (1)
[2021-01-15 03:33:13.810][17292][][gs_ctl]: waiting for server to failover…
[2021-01-15 03:33:14.823][17292][][gs_ctl]: done
[2021-01-15 03:33:14.823][17292][][gs_ctl]: failover completed (/opt/MogDB/data/dn)
确认集群主备状态：双主状态
$ gs_om -t status --detail
[ Cluster State ]
cluster_state : Unavailable
redistributing : No
current_az : AZ_ALL
[ Datanode State ]
node node_ip instance state | node node_ip instance state
--------------------------------------------------------------------------------------------------------------------------------------------------------------------
1 cen7-og1-02 192.168.229.53 6001 /opt/MogDB/data/dn P Primary Normal | 2 cen7-og1-03 192.168.229.54 6002 /opt/MogDB/data/dn S Primary Normal
在确定降为备机的节点关闭并以standy模式启动MogDB服务：
$ gs_ctl start -D /opt/MogDB/data/dn -M standby
[2021-01-15 03:03:08.695][9126][][gs_ctl]: gs_ctl started,datadir is /opt/MogDB/data/dn
[2021-01-15 03:03:08.864][9126][][gs_ctl]: waiting for server to start…
…
[2021-01-15 03:03:10.921][9126][][gs_ctl]: done
[2021-01-15 03:03:10.921][9126][][gs_ctl]: server started (/opt/MogDB/data/dn)
确认集群状态：1节点为主库，2节点为备库，但备库需要修复
$ gs_om -t status --detail
[ Cluster State ]
cluster_state : Degraded
redistributing : No
current_az : AZ_ALL
[ Datanode State ]
node node_ip instance state | node node_ip instance state
--------------------------------------------------------------------------------------------------------------------------------------------------------------------
1 cen7-og1-02 192.168.229.53 6001 /opt/MogDB/data/dn P Primary Normal | 2 cen7-og1-03 192.168.229.54 6002 /opt/MogDB/data/dn S Standby Need repair(WAL)
在备库所在节点执行修复命令：
[omm@cen7-og1-03 ~]$ gs_ctl build -D /opt/MogDB/data/dn [2021-01-15 03:23:57.702][30784][][gs_ctl]: gs_ctl incremental build ,datadir is /opt/MogDB/data/dn waiting for server to shut down… done server stopped [2021-01-15 03:23:58.726][30784][][gs_ctl]: fopen build pid file “/opt/MogDB/data/dn/gs_build.pid” success [2021-01-15 03:23:58.726][30784][][gs_ctl]: fprintf build pid file “/opt/MogDB/data/dn/gs_build.pid” success [2021-01-15 03:23:58.727][30784][][gs_ctl]: fsync build pid file “/opt/MogDB/data/dn/gs_build.pid” success … [2021-01-15 03:24:02.833][30784][dn_6001_6002][gs_ctl]: done [2021-01-15 03:24:02.833][30784][dn_6001_6002][gs_ctl]: server started (/opt/MogDB/data/dn) [2021-01-15 03:24:02.833][30784][dn_6001_6002][gs_ctl]: fopen build pid file “/opt/MogDB/data/dn/gs_build.pid” success [2021-01-15 03:24:02.833][30784][dn_6001_6002][gs_ctl]: fprintf build pid file “/opt/MogDB/data/dn/gs_build.pid” success [2021-01-15 03:24:02.835][30784][dn_6001_6002][gs_ctl]: fsync build pid file “/opt/MogDB/data/dn/gs_build.pid” success
确认集群状态：正常
$ gs_om -t status --detail
[ Cluster State ]
cluster_state : Normal
redistributing : No
current_az : AZ_ALL
[ Datanode State ]
node node_ip instance state | node node_ip instance state
--------------------------------------------------------------------------------------------------------------------------------------------------------------------
1 cen7-og1-02 192.168.229.53 6001 /opt/MogDB/data/dn P Primary Normal | 2 cen7-og1-03 192.168.229.54 6002 /opt/MogDB/data/dn S Standby Normal
保存数据库主备机器信息：确保gs_om -t refreshconf 命令执行成功，否则再次重启会影响数据库状态。
$ gs_om -t refreshconf
Generating dynamic configuration file for all nodes.
Successfully generated dynamic configuration file.
最后修改时间：2021-12-27 11:49:08
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