本文介紹gpdb的master故障及恢復測試以及segment故障恢復測試。

環境介紹：
Gpdb版本：5.5.0 二進制版本
操作系統版本： centos linux 7.0
Master segment: 192.168.1.225/24 hostname: mfsmaster
Stadnby segemnt: 192.168.1.227/24 hostname: server227
Segment 節點1： 192.168.1.227/24 hostname: server227
Segment 節點2： 192.168.1.17/24 hostname: server17
Segment 節點3： 192.168.1.11/24 hostname: server11
每個segment節點上分別運行一個primary segment和一個mirror segment

一、查看原始狀態

select * from gp_segment_configuration;

$ gpstate -f 20180320:13:50:38:021814 gpstate:mfsmaster:gpadmin-[INFO]:-Starting gpstate with args: -f 20180320:13:50:38:021814 gpstate:mfsmaster:gpadmin-[INFO]:-local Greenplum Version: 'postgres (Greenplum Database) 5.5.0 build commit:67afa18296aa238d53a2dfcc724da60ed2f944f0' 20180320:13:50:38:021814 gpstate:mfsmaster:gpadmin-[INFO]:-master Greenplum Version: 'PostgreSQL 8.3.23 (Greenplum Database 5.5.0 build commit:67afa18296aa238d53a2dfcc724da60ed2f944f0) on x86_64-pc-linux-gnu, compiled by GCC gcc (GCC) 6.2.0, 64-bit compiled on Feb 17 2018 15:23:55' 20180320:13:50:38:021814 gpstate:mfsmaster:gpadmin-[INFO]:-Obtaining Segment details from master... 20180320:13:50:38:021814 gpstate:mfsmaster:gpadmin-[INFO]:-Standby master details 20180320:13:50:38:021814 gpstate:mfsmaster:gpadmin-[INFO]:----------------------- 20180320:13:50:38:021814 gpstate:mfsmaster:gpadmin-[INFO]:- Standby address = server227 20180320:13:50:38:021814 gpstate:mfsmaster:gpadmin-[INFO]:- Standby data directory = /home/gpadmin/master/gpseg-1 20180320:13:50:38:021814 gpstate:mfsmaster:gpadmin-[INFO]:- Standby port = 5432 20180320:13:50:38:021814 gpstate:mfsmaster:gpadmin-[INFO]:- Standby PID = 22279 20180320:13:50:38:021814 gpstate:mfsmaster:gpadmin-[INFO]:- Standby status = Standby host passive 20180320:13:50:38:021814 gpstate:mfsmaster:gpadmin-[INFO]:-------------------------------------------------------------- 20180320:13:50:38:021814 gpstate:mfsmaster:gpadmin-[INFO]:--pg_stat_replication 20180320:13:50:38:021814 gpstate:mfsmaster:gpadmin-[INFO]:-------------------------------------------------------------- 20180320:13:50:38:021814 gpstate:mfsmaster:gpadmin-[INFO]:--WAL Sender State: streaming 20180320:13:50:38:021814 gpstate:mfsmaster:gpadmin-[INFO]:--Sync state: sync 20180320:13:50:38:021814 gpstate:mfsmaster:gpadmin-[INFO]:--Sent Location: 0/CF2C470 20180320:13:50:38:021814 gpstate:mfsmaster:gpadmin-[INFO]:--Flush Location: 0/CF2C470 20180320:13:50:38:021814 gpstate:mfsmaster:gpadmin-[INFO]:--Replay Location: 0/CF2C470 20180320:13:50:38:021814 gpstate:mfsmaster:gpadmin-[INFO]:--------------------------------------------------------------

二、master主從切換
1、模擬當前主庫宕機，這里直接采用killall gpadmin用戶下的所有進程來模擬

2、在master standby節點（227服務器上）進行執行切換命令，提升227為master

$ gpactivatestandby -d master/gpseg-1/ 20180320:13:53:20:030558 gpactivatestandby:server227:gpadmin-[INFO]:------------------------------------------------------ 20180320:13:53:20:030558 gpactivatestandby:server227:gpadmin-[INFO]:-Standby data directory = /home/gpadmin/master/gpseg-1 20180320:13:53:20:030558 gpactivatestandby:server227:gpadmin-[INFO]:-Standby port = 5432 20180320:13:53:20:030558 gpactivatestandby:server227:gpadmin-[INFO]:-Standby running = yes 20180320:13:53:20:030558 gpactivatestandby:server227:gpadmin-[INFO]:-Force standby activation = no 20180320:13:53:20:030558 gpactivatestandby:server227:gpadmin-[INFO]:------------------------------------------------------ Do you want to continue with standby master activation? Yy|Nn (default=N): > y 20180320:13:53:26:030558 gpactivatestandby:server227:gpadmin-[INFO]:-found standby postmaster process 20180320:13:53:26:030558 gpactivatestandby:server227:gpadmin-[INFO]:-Updating transaction files filespace flat files... 20180320:13:53:26:030558 gpactivatestandby:server227:gpadmin-[INFO]:-Updating temporary files filespace flat files... 20180320:13:53:26:030558 gpactivatestandby:server227:gpadmin-[INFO]:-Promoting standby... 20180320:13:53:26:030558 gpactivatestandby:server227:gpadmin-[DEBUG]:-Waiting for connection... 20180320:13:53:27:030558 gpactivatestandby:server227:gpadmin-[INFO]:-Standby master is promoted 20180320:13:53:27:030558 gpactivatestandby:server227:gpadmin-[INFO]:-Reading current configuration... 20180320:13:53:27:030558 gpactivatestandby:server227:gpadmin-[DEBUG]:-Connecting to dbname='postgres' 20180320:13:53:27:030558 gpactivatestandby:server227:gpadmin-[INFO]:-Writing the gp_dbid file - /home/gpadmin/master/gpseg-1/gp_dbid... 20180320:13:53:27:030558 gpactivatestandby:server227:gpadmin-[INFO]:-But found an already existing file. 20180320:13:53:27:030558 gpactivatestandby:server227:gpadmin-[INFO]:-Hence removed that existing file. 20180320:13:53:27:030558 gpactivatestandby:server227:gpadmin-[INFO]:-Creating a new file... 20180320:13:53:27:030558 gpactivatestandby:server227:gpadmin-[INFO]:-Wrote dbid: 1 to the file. 20180320:13:53:27:030558 gpactivatestandby:server227:gpadmin-[INFO]:-Now marking it as read only... 20180320:13:53:27:030558 gpactivatestandby:server227:gpadmin-[INFO]:-Verifying the file... 20180320:13:53:27:030558 gpactivatestandby:server227:gpadmin-[INFO]:------------------------------------------------------ 20180320:13:53:27:030558 gpactivatestandby:server227:gpadmin-[INFO]:-The activation of the standby master has completed successfully. 20180320:13:53:27:030558 gpactivatestandby:server227:gpadmin-[INFO]:-server227 is now the new primary master. 20180320:13:53:27:030558 gpactivatestandby:server227:gpadmin-[INFO]:-You will need to update your user access mechanism to reflect 20180320:13:53:27:030558 gpactivatestandby:server227:gpadmin-[INFO]:-the change of master hostname. 20180320:13:53:27:030558 gpactivatestandby:server227:gpadmin-[INFO]:-Do not re-start the failed master while the fail-over master is 20180320:13:53:27:030558 gpactivatestandby:server227:gpadmin-[INFO]:-operational, this could result in database corruption! 20180320:13:53:27:030558 gpactivatestandby:server227:gpadmin-[INFO]:-MASTER_DATA_DIRECTORY is now /home/gpadmin/master/gpseg-1 if 20180320:13:53:27:030558 gpactivatestandby:server227:gpadmin-[INFO]:-this has changed as a result of the standby master activation, remember 20180320:13:53:27:030558 gpactivatestandby:server227:gpadmin-[INFO]:-to change this in any startup scripts etc, that may be configured 20180320:13:53:27:030558 gpactivatestandby:server227:gpadmin-[INFO]:-to set this value. 20180320:13:53:27:030558 gpactivatestandby:server227:gpadmin-[INFO]:-MASTER_PORT is now 5432, if this has changed, you 20180320:13:53:27:030558 gpactivatestandby:server227:gpadmin-[INFO]:-may need to make additional configuration changes to allow access 20180320:13:53:27:030558 gpactivatestandby:server227:gpadmin-[INFO]:-to the Greenplum instance. 20180320:13:53:27:030558 gpactivatestandby:server227:gpadmin-[INFO]:-Refer to the Administrator Guide for instructions on how to re-activate 20180320:13:53:27:030558 gpactivatestandby:server227:gpadmin-[INFO]:-the master to its previous state once it becomes available. 20180320:13:53:27:030558 gpactivatestandby:server227:gpadmin-[INFO]:-Query planner statistics must be updated on all databases 20180320:13:53:27:030558 gpactivatestandby:server227:gpadmin-[INFO]:-following standby master activation. 20180320:13:53:27:030558 gpactivatestandby:server227:gpadmin-[INFO]:-When convenient, run ANALYZE against all user databases. 20180320:13:53:27:030558 gpactivatestandby:server227:gpadmin-[INFO]:------------------------------------------------------

3、測試提升后的主庫是否正常

$ psql -d postgres -c 'ANALYZE' postgres=# select * from gp_segment_configuration;

4、這里可能需要同步配置一下pg_hba.conf文件，才能通過客戶端進行遠程連接

到這里我們已經完成了master節點的故障切換工作。

三、添加新的master standby
1、 在225服務器上執行gpstart -a命令啟動gpdb數據庫的時候報錯”error: Standby active, this node no more can act as master”。當standby 提升為master的時候，原master服務器從故障中恢復過來，需要以standby的角色加入

2、在原master服務器225上的數據進行備份

$ cd master/ $ ls gpseg-1 $ mv gpseg-1/ backup-gpseg-1

3、在當前master服務器227上進行 gpinitstandby添加225為standby

$ gpinitstandby -s mfsmaster $ gpstate -f

四、primary segment和mirror segment切換
1、首先我們來捋一下當前的數據庫環境
Master segment: 192.168.1.227/24 hostname: server227
Stadnby segemnt: 192.168.1.225/24 hostname: mfsmaster
Segment 節點1： 192.168.1.227/24 hostname: server227
Segment 節點2： 192.168.1.17/24 hostname: server17
Segment 節點3： 192.168.1.11/24 hostname: server11
每個segment節點上分別運行一個primary segment和一個mirror segment

2、接著我們采用同樣的方式把227服務器上gpadmin用戶的所有進行殺掉

$ killall -u gpadmin

3、在225服務器上執行切換master命令

$ gpactivatestandby -d master/gpseg-1/

4、完成切換后使用客戶端工具連接查看segment狀態，可以看到227服務器上的server227
的primary和mirror節點都已經宕機了。

5、這里為了方面查看，我們使用greenplum-cc-web工具來查看集群狀態

$ gpcmdr --start hbjy

需要將pg_hba.conf文件還原回去，因為227上所有的segment已經宕掉，執行gpstop -u命令會有報錯

在segment status頁面中可以看到當前segment的狀態是異常的。server11上有兩組的primary segment，這很危險，如果不幸server11也宕機了，整個集群的狀態就變成不可用了。

6、將server227做為master standby重新加入集群

$ cd master/ $ mv gpseg-1/ backupgpseg-1 $ gpinitstandby -s server227

7、在master上重啟集群

$ gpstop -M immediate $ gpstart -a

8、在master上恢復集群

$ gprecoverseg

雖然所有的segment均已啟動，但server11上有還是有兩組的primary segment

9、在master上恢復segment節點分布到原始狀態

$ gprecoverseg -r

參考文檔：
http://greenplum.org/docs/520/admin_guide/highavail/topics/g-restoring-master-mirroring-after-a-recovery.html

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