GreenPlum failover，primary和mirror切换实验 -- 重要
GP failover，primary和mirror切换实验
http://blog.sina.com.cn/s/blog_9869114e0101k1nc.html
一、恢复失败的segment
出现segment节点down，恢复GP的思路：
if
"segment down" then
case "determine case(errer,message,log,gpstate and so on)"
when "data error[missing or corrupted data directory]"
then
if "mirror segment是否可用" then
"gprecoverseg --从mirror segment中恢复primary segment丢失的部分"
else
"rebuild gp database system from backup file"
end if
when "进程错误--postmaster process not is running"
then
if "mirror segment是否可用" then
"gprecoverseg --从mirror segment中恢复primary segment丢失的部分"
else
"重启GP数据库--gpstop gpstart"
end if
when "主机出现故障--dns,network,host down and so on"
then
if "主机故障是否恢复" then
"故障恢复，切换主机在线"
if "mirror segment是否可用" then
"gprecoverseg --从mirror segment中恢复primary segment丢失的部分"
else
"重启GP数据库--gpstop gpstart"
end if
elsif "mirror segment是否可用"
then
"从备机上恢复primary segment丢失的数据 --gprecoverseg -p | -s"
else
"rebuild gp database system from backup file"
end if
end case
end if
a、当发生主机出现故障，主机所有的primary和mirror节点都会标注为down，并踢出集群。如果GP集群没有部署mirror segment，那么整个GP集群将会宕机。
b、通过gprecoverseg 工具恢复segment丢失的数据部分，恢复期间，数据库写的操作将暂时的延缓。
c、gpreceverseg完成之后，数据库将进行重新同步模式，并开始复制改变的文件。这些操作都都是通过后台进程来完成，在这个阶段数据库是可以进行正常的服务。
d、当重新同步完成，系统编程同步化状态，可以通过gpstate -m查询
e、主备切换--切换segment到预设角色（primary，mirror）。当出现segment故障时，mirror segment会替换故障的primary segment，成为primary segment，之前故障的primary segment在使用gprecoverseg恢复后，之前的primary不会切回primary segment，而是变为mirror segment。
二、Preferred role和current role的概念
当配置了mirror segment时，存在Preferred role和current role的概念，当primary segment节点down了，mirror segment节点会接管primary的位置，成为新的primary segment，之前down掉的primary segment在online后会成为mirror segment。那么预设角色是指正常情况下primary segment各种的位置，当前角色是只出现failover后，mirror取代之前的primary，当前的segment的角色。
# 显示primary、mirror segment存在的问题
gpstate -e
#显示mirror segment实例的当前角色，同步状态等信息
gpstate -m
#可以通过gprecover -r将处于当前角色的segment切回预设角色。
gprecoverseg -r
# 显示primary、mirror segment存在的问题
gpstate -e
案例1：
3个primary segment+3个mirror segment+ 1个master server模拟一个主机宕机的情况。
分析可能出现的问题：
一个主机host2宕机，上面相应的1个primary segment和1个mirror segment都
会down掉。由于做了mirror，host2 primary对于的mirror在host1上，会被激活，成为新的primary节点,当前的角色也从mirror切换成primary。故障的primary节点在online后，会成功新的mirror节点，当前角色从primary角色切换成mirror角色。
模拟故障前的信息确认：
$ gpstate --查看gp数据库的总体状态
- Master instance = Active --master状态
- Master standby = No master standby configured
- Total segment instance count from metadata = 6 --segment节点数
-----------------------------------------------------
- Primary Segment Status
-----------------------------------------------------
- Total primary segments = 3
- Total primary segment valid (at master) = 3
- Total primary segment failures (at master) = 0
- Total number of postmaster.pid files missing = 0
- Total number of postmaster.pid files found = 3
- Total number of postmaster.pid PIDs missing = 0
- Total number of postmaster.pid PIDs found = 3
- Total number of /tmp lock files missing = 0
- Total number of /tmp lock files found = 3
- Total number postmaster processes missing = 0
- Total number postmaster processes found = 3
-----------------------------------------------------
- Mirror Segment Status
-----------------------------------------------------
- Total mirror segments = 3
- Total mirror segment valid (at master) = 3
- Total mirror segment failures (at master) = 0
- Total number of postmaster.pid files missing = 0
- Total number of postmaster.pid files found = 3
- Total number of postmaster.pid PIDs missing = 0
- Total number of postmaster.pid PIDs found = 3
- Total number of /tmp lock files missing = 0
$ gpstate -m --查看mirror节点情况
-Obtaining Segment details from master...
--------------------------------------------------------------
--Current GPDB mirror list and status
--Type = Spread
--------------------------------------------------------------
- Mirror Datadir Port Status Data Status
- gp02 /gpsegment2/gpseg0 50000 Passive Synchronized
- gp03 /gpsegment2/gpseg1 50000 Passive Synchronized
- gp01 /gpsegment2/gpseg2 50000 Passive Synchronized
--------------------------------------------------------------
$ gpstate -e --显示primary、mirror segment存在的问题
-Gathering data from segments... ----------------------------------------------------- -Segment Mirroring Status Report ----------------------------------------------------- -All segments are running normally
模拟gp02的主机故障：
[gp02]# killall -u gpadmin --杀掉gp02的gpadmin下所有的进程
[root@gp02 ~]# killall -u gpadmin
[root@gp02 ~]# ps -ef | grep gpadmin
root 6733 3155 0 03:26 pts/0 00:00:00 grep gpadmin
查询故障后，gp数据库的状态：
$ gpstate -e
-----------------------------------------------------
-Segment Mirroring Status Report
-----------------------------------------------------
-Segments with Primary and Mirror Roles Switched
- Current Primary Port Mirror Port
- gp03 50000 gp02 40000
-----------------------------------------------------
-Primaries in Change Tracking
- Current Primary Port Change tracking size Mirror Port
- gp01 40000 100 MB gp02 50000
- gp03 50000 100 MB gp02 40000
--gp02的primary segment对于的mirror segment的位置：gp03的/gpsegment2/gpseg1。
显示mirror segment实例的当前角色，同步状态等信息
$ gpstate -m
[INFO]:-------------------------------------------------------------- [INFO]:--Current GPDB mirror list and status [INFO]:--Type = Spread
[INFO]:-------------------------------------------------------------- [INFO]:- Mirror Datadir Port Status Data Status [WARNING]:-gp02 /gpsegment2/gpseg0 50000 Failed
[INFO]:- gp03 /gpsegment2/gpseg1 50000 Acting as Primary Change Tracking [INFO]:- gp01 /gpsegment2/gpseg2 50000 Passive Synchronized [INFO]:-------------------------------------------------------------- [WARNING]:-1 segment(s) configured as mirror(s) are acting as primaries [WARNING]:-1 segment(s) configured as mirror(s) have failed [WARNING]:-1 mirror segment(s) acting as primaries are in change tracking
查询结果gpseg0 的mirror segment 状态为failed，gpseg1的mirror成为了primary节点。
[INFO]:----------------------------------------------------- [INFO]:- Segment Info [INFO]:- Hostname = gp02 [INFO]:- Address = gp02 [INFO]:- Datadir = /gpsegment2/gpseg0 [INFO]:- Port = 50000 [INFO]:- Mirroring Info [INFO]:- Current role = Mirror [INFO]:- Preferred role = Mirror [WARNING]:- Mirror status = Out of Sync <<<<<<<< [INFO]:- Status [WARNING]:- PID = Not found <<<<<<<< [WARNING]:- Configuration reports status as = Down <<<<<<<< [WARNING]:- Segment status = Down in configuration <<<<<<<< [INFO]:----------------------------------------------------- [INFO]:- Segment Info [INFO]:- Hostname = gp03 [INFO]:- Address = gp03 [INFO]:- Datadir = /gpsegment2/gpseg1 [INFO]:- Port = 50000 [INFO]:- Mirroring Info [INFO]:- Current role = Primary [INFO]:- Preferred role = Mirror [INFO]:- Mirror status = Change Tracking [INFO]:- Change Tracking Info [INFO]:- Change tracking data size = 100 MB [INFO]:- Status [INFO]:- PID = 5901 [INFO]:- Configuration reports status as = Up [INFO]:- Database status = Up [INFO]:----------------------------------------------------- [INFO]:- Segment Info [INFO]:- Hostname = gp02 [INFO]:- Address = gp02 [INFO]:- Datadir = /gpsegment1/gpseg1 [INFO]:- Port = 40000 [INFO]:- Mirroring Info [INFO]:- Current role = Mirror [INFO]:- Preferred role = Primary [WARNING]:- Mirror status = Out of Sync <<<<<<<< [INFO]:- Status [WARNING]:- PID = Not found <<<<<<<< [WARNING]:- Configuration reports status as = Down <<<<<<<< [WARNING]:- Segment status = Down in configuration <<<<<<<< [INFO]:-----------------------------------------------------
确定主机无故障后，恢复丢失的数据：
[gpadmin@gp01 gpsegment2]$ gprecoverseg
20140310:04:09:19:021098 gprecoverseg:gp01:gpadmin-[INFO]:-Starting gprecoverseg with args:
20140310:04:09:19:021098 gprecoverseg:gp01:gpadmin-[INFO]:-local Greenplum Version: 'postgres (Greenplum Database) 4.2.2.4 build 1 Community Edition'
20140310:04:09:19:021098 gprecoverseg:gp01:gpadmin-[INFO]:-master Greenplum Version: 'PostgreSQL 8.2.15 (Greenplum Database 4.2.2.4 build 1 Community Edition) on x86_64-unknown-linux-gnu, compiled by GCC gcc (GCC) 4.4.2 compiled on Oct 17 2012 11:52:28'
20140310:04:09:19:021098 gprecoverseg:gp01:gpadmin-[INFO]:-Obtaining Segment details from master...
20140310:04:09:20:021098 gprecoverseg:gp01:gpadmin-[INFO]:-Greenplum instance recovery parameters
20140310:04:09:20:021098 gprecoverseg:gp01:gpadmin-[INFO]:----------------------------------------------------------
20140310:04:09:20:021098 gprecoverseg:gp01:gpadmin-[INFO]:-Recovery type = Standard
20140310:04:09:20:021098 gprecoverseg:gp01:gpadmin-[INFO]:----------------------------------------------------------
20140310:04:09:20:021098 gprecoverseg:gp01:gpadmin-[INFO]:-Recovery 1 of 2
20140310:04:09:20:021098 gprecoverseg:gp01:gpadmin-[INFO]:----------------------------------------------------------
20140310:04:09:20:021098 gprecoverseg:gp01:gpadmin-[INFO]:- Synchronization mode = Incremental
20140310:04:09:20:021098 gprecoverseg:gp01:gpadmin-[INFO]:- Failed instance host = gp02
20140310:04:09:20:021098 gprecoverseg:gp01:gpadmin-[INFO]:- Failed instance address = gp02
20140310:04:09:20:021098 gprecoverseg:gp01:gpadmin-[INFO]:- Failed instance directory = /gpsegment2/gpseg0
20140310:04:09:20:021098 gprecoverseg:gp01:gpadmin-[INFO]:- Failed instance port = 50000
20140310:04:09:20:021098 gprecoverseg:gp01:gpadmin-[INFO]:- Failed instance replication port = 51000
20140310:04:09:20:021098 gprecoverseg:gp01:gpadmin-[INFO]:- Recovery Source instance host = gp01
20140310:04:09:20:021098 gprecoverseg:gp01:gpadmin-[INFO]:- Recovery Source instance address = gp01
20140310:04:09:20:021098 gprecoverseg:gp01:gpadmin-[INFO]:- Recovery Source instance directory = /gpsegment1/gpseg0
20140310:04:09:20:021098 gprecoverseg:gp01:gpadmin-[INFO]:- Recovery Source instance port = 40000
20140310:04:09:20:021098 gprecoverseg:gp01:gpadmin-[INFO]:- Recovery Source instance replication port = 41000
20140310:04:09:20:021098 gprecoverseg:gp01:gpadmin-[INFO]:- Recovery Target = in-place
20140310:04:09:20:021098 gprecoverseg:gp01:gpadmin-[INFO]:----------------------------------------------------------
20140310:04:09:20:021098 gprecoverseg:gp01:gpadmin-[INFO]:-Recovery 2 of 2
20140310:04:09:20:021098 gprecoverseg:gp01:gpadmin-[INFO]:----------------------------------------------------------
20140310:04:09:20:021098 gprecoverseg:gp01:gpadmin-[INFO]:- Synchronization mode = Incremental
20140310:04:09:20:021098 gprecoverseg:gp01:gpadmin-[INFO]:- Failed instance host = gp02
20140310:04:09:20:021098 gprecoverseg:gp01:gpadmin-[INFO]:- Failed instance address = gp02
20140310:04:09:20:021098 gprecoverseg:gp01:gpadmin-[INFO]:- Failed instance directory = /gpsegment1/gpseg1
20140310:04:09:20:021098 gprecoverseg:gp01:gpadmin-[INFO]:- Failed instance port = 40000
20140310:04:09:20:021098 gprecoverseg:gp01:gpadmin-[INFO]:- Failed instance replication port = 41000
20140310:04:09:20:021098 gprecoverseg:gp01:gpadmin-[INFO]:- Recovery Source instance host = gp03
20140310:04:09:20:021098 gprecoverseg:gp01:gpadmin-[INFO]:- Recovery Source instance address = gp03
20140310:04:09:20:021098 gprecoverseg:gp01:gpadmin-[INFO]:- Recovery Source instance directory = /gpsegment2/gpseg1
20140310:04:09:20:021098 gprecoverseg:gp01:gpadmin-[INFO]:- Recovery Source instance port = 50000
20140310:04:09:20:021098 gprecoverseg:gp01:gpadmin-[INFO]:- Recovery Source instance replication port = 51000
20140310:04:09:20:021098 gprecoverseg:gp01:gpadmin-[INFO]:- Recovery Target = in-place
20140310:04:09:20:021098 gprecoverseg:gp01:gpadmin-[INFO]:----------------------------------------------------------
Continue with segment recovery procedure Yy|Nn (default=N):
> y
20140310:04:09:23:021098 gprecoverseg:gp01:gpadmin-[INFO]:-2 segment(s) to recover
20140310:04:09:23:021098 gprecoverseg:gp01:gpadmin-[INFO]:-Ensuring 2 failed segment(s) are stopped
updating flat files
20140310:04:09:26:021098 gprecoverseg:gp01:gpadmin-[INFO]:-Updating configuration with new mirrors
20140310:04:09:27:021098 gprecoverseg:gp01:gpadmin-[INFO]:-Updating mirrors
.
20140310:04:09:28:021098 gprecoverseg:gp01:gpadmin-[INFO]:-Starting mirrors
20140310:04:09:28:021098 gprecoverseg:gp01:gpadmin-[INFO]:-Commencing parallel primary and mirror segment instance startup, please wait...
...
20140310:04:09:31:021098 gprecoverseg:gp01:gpadmin-[INFO]:-Process results...
20140310:04:09:31:021098 gprecoverseg:gp01:gpadmin-[INFO]:-Updating configuration to mark mirrors up
20140310:04:09:31:021098 gprecoverseg:gp01:gpadmin-[INFO]:-Updating primaries
20140310:04:09:31:021098 gprecoverseg:gp01:gpadmin-[INFO]:-Commencing parallel primary conversion of 2 segments, please wait...
..
20140310:04:09:33:021098 gprecoverseg:gp01:gpadmin-[INFO]:-Process results...
20140310:04:09:33:021098 gprecoverseg:gp01:gpadmin-[INFO]:-Done updating primaries
20140310:04:09:33:021098 gprecoverseg:gp01:gpadmin-[INFO]:-******************************************************************
20140310:04:09:33:021098 gprecoverseg:gp01:gpadmin-[INFO]:-Updating segments for resynchronization is completed.
20140310:04:09:33:021098 gprecoverseg:gp01:gpadmin-[INFO]:-For segments updated successfully, resynchronization will continue in the background.
20140310:04:09:33:021098 gprecoverseg:gp01:gpadmin-[INFO]:-
20140310:04:09:33:021098 gprecoverseg:gp01:gpadmin-[INFO]:-Use gpstate -s to check the resynchronization progress.
20140310:04:09:33:021098 gprecoverseg:gp01:gpadmin-[INFO]:-******************************************************************
a、gprecoverseg才用 Synchronization mode恢复gp02的segment节点丢失的数据。
b、采用增量同步的方式恢复/gpsegment1/gpseg1丢失的数据。--gp02 primary
c、采用增量同步的方式恢复/gpsegment2/gpseg0丢失的数据。--gp01 primary的mirror
恢复后查询gp数据库的状态：
$ gpstate -e --查询mirror存在的错误，查询显示gp02的primary节点被mirror替换掉，目前的primary的位置在gp03上。
[INFO]:-----------------------------------------------------
[INFO]:-Segment Mirroring Status Report
[INFO]:-----------------------------------------------------
[INFO]:-Segments with Primary and Mirror Roles Switched
[INFO]:- Current Primary Port Mirror Port
[INFO]:- gp03 50000 gp02 40000
$ gpstate -m
[INFO]:-Obtaining Segment details from master..
[INFO]:--------------------------------------------------------------
[INFO]:--Current GPDB mirror list and status
[INFO]:--Type = Spread
[INFO]:--------------------------------------------------------------
[INFO]:- Mirror Datadir Port Status Data Status
[INFO]:- gp02 /gpsegment2/gpseg0 50000 Passive Synchronized
[INFO]:- gp03 /gpsegment2/gpseg1 50000 Acting as Primary Synchronized
[INFO]:- gp01 /gpsegment2/gpseg2 50000 Passive Synchronized
[INFO]:--------------------------------------------------------------
[WARNING]:-1 segment(s) configured as mirror(s) are acting as primaries
切换current role到prefered role
[gpadmin@gp01 gpsegment2]$ gprecoverseg -r
20140310:04:35:51:021852 gprecoverseg:gp01:gpadmin-[INFO]:-Starting gprecoverseg with args: -r
20140310:04:35:51:021852 gprecoverseg:gp01:gpadmin-[INFO]:-local Greenplum Version: 'postgres (Greenplum Database) 4.2.2.4 build 1 Community Edition'
20140310:04:35:51:021852 gprecoverseg:gp01:gpadmin-[INFO]:-master Greenplum Version: 'PostgreSQL 8.2.15 (Greenplum Database 4.2.2.4 build 1 Community Edition) on x86_64-unknown-linux-gnu, compiled by GCC gcc (GCC) 4.4.2 compiled on Oct 17 2012 11:52:28'
20140310:04:35:51:021852 gprecoverseg:gp01:gpadmin-[INFO]:-Obtaining Segment details from master...
20140310:04:35:51:021852 gprecoverseg:gp01:gpadmin-[INFO]:-Greenplum instance recovery parameters
20140310:04:35:51:021852 gprecoverseg:gp01:gpadmin-[INFO]:----------------------------------------------------------
20140310:04:35:51:021852 gprecoverseg:gp01:gpadmin-[INFO]:-Recovery type = Rebalance
20140310:04:35:51:021852 gprecoverseg:gp01:gpadmin-[INFO]:----------------------------------------------------------
20140310:04:35:51:021852 gprecoverseg:gp01:gpadmin-[INFO]:-Unbalanced segment 1 of 2
20140310:04:35:51:021852 gprecoverseg:gp01:gpadmin-[INFO]:----------------------------------------------------------
20140310:04:35:51:021852 gprecoverseg:gp01:gpadmin-[INFO]:- Unbalanced instance host = gp03
20140310:04:35:51:021852 gprecoverseg:gp01:gpadmin-[INFO]:- Unbalanced instance address = gp03
20140310:04:35:51:021852 gprecoverseg:gp01:gpadmin-[INFO]:- Unbalanced instance directory = /gpsegment2/gpseg1
20140310:04:35:51:021852 gprecoverseg:gp01:gpadmin-[INFO]:- Unbalanced instance port = 50000
20140310:04:35:51:021852 gprecoverseg:gp01:gpadmin-[INFO]:- Unbalanced instance replication port = 51000
20140310:04:35:51:021852 gprecoverseg:gp01:gpadmin-[INFO]:- Balanced role = Mirror
20140310:04:35:51:021852 gprecoverseg:gp01:gpadmin-[INFO]:- Current role = Primary
20140310:04:35:51:021852 gprecoverseg:gp01:gpadmin-[INFO]:----------------------------------------------------------
20140310:04:35:51:021852 gprecoverseg:gp01:gpadmin-[INFO]:-Unbalanced segment 2 of 2
20140310:04:35:51:021852 gprecoverseg:gp01:gpadmin-[INFO]:----------------------------------------------------------
20140310:04:35:51:021852 gprecoverseg:gp01:gpadmin-[INFO]:- Unbalanced instance host = gp02
20140310:04:35:51:021852 gprecoverseg:gp01:gpadmin-[INFO]:- Unbalanced instance address = gp02
20140310:04:35:51:021852 gprecoverseg:gp01:gpadmin-[INFO]:- Unbalanced instance directory = /gpsegment1/gpseg1
20140310:04:35:51:021852 gprecoverseg:gp01:gpadmin-[INFO]:- Unbalanced instance port = 40000
20140310:04:35:51:021852 gprecoverseg:gp01:gpadmin-[INFO]:- Unbalanced instance replication port = 41000
20140310:04:35:51:021852 gprecoverseg:gp01:gpadmin-[INFO]:- Balanced role = Primary
20140310:04:35:51:021852 gprecoverseg:gp01:gpadmin-[INFO]:- Current role = Mirror
20140310:04:35:51:021852 gprecoverseg:gp01:gpadmin-[INFO]:----------------------------------------------------------
20140310:04:35:51:021852 gprecoverseg:gp01:gpadmin-[WARNING]:-This operation will cancel queries that are currently executing.
20140310:04:35:51:021852 gprecoverseg:gp01:gpadmin-[WARNING]:-Connections to the database however will not be interrupted.
Continue with segment rebalance procedure Yy|Nn (default=N):
> y
20140310:04:36:01:021852 gprecoverseg:gp01:gpadmin-[INFO]:-Getting unbalanced segments
20140310:04:36:01:021852 gprecoverseg:gp01:gpadmin-[INFO]:-Stopping unbalanced primary segments...
..
20140310:04:36:03:021852 gprecoverseg:gp01:gpadmin-[INFO]:-Triggering segment reconfiguration
20140310:04:36:07:021852 gprecoverseg:gp01:gpadmin-[INFO]:-Starting segment synchronization
............
20140310:04:36:20:021852 gprecoverseg:gp01:gpadmin-[INFO]:-******************************************************************
20140310:04:36:20:021852 gprecoverseg:gp01:gpadmin-[INFO]:-The rebalance operation has completed successfully.
20140310:04:36:20:021852 gprecoverseg:gp01:gpadmin-[INFO]:-There is a resynchronization running in the background to bring all
20140310:04:36:20:021852 gprecoverseg:gp01:gpadmin-[INFO]:-segments in sync.
20140310:04:36:20:021852 gprecoverseg:gp01:gpadmin-[INFO]:-
20140310:04:36:20:021852 gprecoverseg:gp01:gpadmin-[INFO]:-Use gpstate -s to check the resynchronization progress.
20140310:04:36:20:021852 gprecoverseg:gp01:gpadmin-[INFO]:-******************************************************************
查询切换后的状态：
$ gpstate -e
[INFO]:-Starting gpstate with args: -e
[INFO]:-local Greenplum Version: 'postgres (Greenplum Database) 4.2.2.4 build 1 Community Edition'
[INFO]:-master Greenplum Version: 'PostgreSQL 8.2.15 (Greenplum Database 4.2.2.4 build 1 Community Edition) on x86_64-unknown-linux-gnu, compiled by GCC gcc (GCC) 4.4.2 compiled on Oct 17 2012 11:52:28'
[INFO]:-Obtaining Segment details from master...
[INFO]:-Gathering data from segments...
[INFO]:-----------------------------------------------------
[INFO]:-Segment Mirroring Status Report
[INFO]:-----------------------------------------------------
[INFO]:-Segment Pairs in Resynchronization
[INFO]:- Current Primary Port Resync mode Est. resync progress Data synced Est. total to sync Est. resync end time Change tracking size Mirror Port
[INFO]:- gp02 40000 Incremental 100% 224 kB Sync complete; awaiting config change 100 MB gp03 50000
再次查询gp状态：
$ gpstate -e
[INFO]:-Starting gpstate with args: -e
[INFO]:-local Greenplum Version: 'postgres (Greenplum Database) 4.2.2.4 build 1 Community Edition'
[INFO]:-master Greenplum Version: 'PostgreSQL 8.2.15 (Greenplum Database 4.2.2.4 build 1 Community Edition) on x86_64-unknown-linux-gnu, compiled by GCC gcc (GCC) 4.4.2 compiled on Oct 17 2012 11:52:28'
[INFO]:-Obtaining Segment details from master...
[INFO]:-Gathering data from segments...
[INFO]:-----------------------------------------------------
[INFO]:-Segment Mirroring Status Report
[INFO]:-----------------------------------------------------
[INFO]:-All segments are running normally
查询prefer role和current role：
[INFO]:-----------------------------------------------------
[INFO]:--Master Configuration & Status
[INFO]:-----------------------------------------------------
[INFO]:- Master host = gp01
[INFO]:- Master postgres process ID = 12423
[INFO]:- Master data directory = /gpmaster/gpseg-1
[INFO]:- Master port = 5432
[INFO]:- Master current role= dispatch
[INFO]:- Greenplum initsystem version = 4.2.2.4 build 1 Community Edition
[INFO]:- Greenplum current version= PostgreSQL 8.2.15 (Greenplum Database 4.2.2.4 build 1 Community Edition) on x86_64-unknown-linux-gnu, compiled by GCC gcc (GCC) 4.4.2 compiled on Oct 17 2012 11:52:28
[INFO]:- Postgres version = 8.2.15
[INFO]:- Master standby = No master standby configured
[INFO]:-----------------------------------------------------
[INFO]:-Segment Instance Status Report
[INFO]:-----------------------------------------------------
[INFO]:- Segment Info
[INFO]:-Hostname = gp01
[INFO]:-Address = gp01
[INFO]:-Datadir = /gpsegment1/gpseg0
[INFO]:-Port= 40000
[INFO]:- Mirroring Info
[INFO]:-Current role = Primary
[INFO]:-Preferred role = Primary
[INFO]:-Mirror status = Synchronized
[INFO]:- Status
[INFO]:-PID = 12390
[INFO]:-Configuration reports status as = Up
[INFO]:-Database status = Up
[INFO]:-----------------------------------------------------
[INFO]:- Segment Info
[INFO]:-Hostname = gp02
[INFO]:-Address = gp02
[INFO]:-Datadir = /gpsegment2/gpseg0
[INFO]:-Port= 50000
[INFO]:- Mirroring Info
[INFO]:-Current role = Mirror
[INFO]:-Preferred role = Mirror
[INFO]:-Mirror status = Synchronized
[INFO]:- Status
[INFO]:-PID = 10689
[INFO]:-Configuration reports status as = Up
[INFO]:-Segment status = Up
[INFO]:-----------------------------------------------------
[INFO]:- Segment Info
[INFO]:-Hostname = gp02
[INFO]:-Address = gp02
[INFO]:-Datadir = /gpsegment1/gpseg1
[INFO]:-Port= 40000
[INFO]:- Mirroring Info
[INFO]:-Current role = Primary
[INFO]:-Preferred role = Primary
[INFO]:-Mirror status = Synchronized
[INFO]:- Status
[INFO]:-PID = 10695
[INFO]:-Configuration reports status as = Up
[INFO]:-Database status = Up
[INFO]:-----------------------------------------------------
[INFO]:- Segment Info
[INFO]:-Hostname = gp03
[INFO]:-Address = gp03
[INFO]:-Datadir = /gpsegment2/gpseg1
[INFO]:-Port= 50000
[INFO]:- Mirroring Info
[INFO]:-Current role = Mirror
[INFO]:-Preferred role = Mirror
[INFO]:-Mirror status = Synchronized
[INFO]:- Status
[INFO]:-PID = 10946
[INFO]:-Configuration reports status as = Up
[INFO]:-Segment status = Up
[INFO]:-----------------------------------------------------
[INFO]:- Segment Info
[INFO]:-Hostname = gp03
[INFO]:-Address = gp03
[INFO]:-Datadir = /gpsegment1/gpseg2
[INFO]:-Port= 40000
[INFO]:- Mirroring Info
[INFO]:-Current role = Primary
[INFO]:-Preferred role = Primary
[INFO]:-Mirror status = Synchronized
[INFO]:- Status
[INFO]:-PID = 5907
[INFO]:-Configuration reports status as = Up
[INFO]:-Database status = Up
[INFO]:-----------------------------------------------------
[INFO]:- Segment Info
[INFO]:-Hostname = gp01
[INFO]:-Address = gp01
[INFO]:-Datadir = /gpsegment2/gpseg2
[INFO]:-Port= 50000
[INFO]:- Mirroring Info
[INFO]:-Current role = Mirror
[INFO]:-Preferred role = Mirror
[INFO]:-Mirror status = Synchronized
[INFO]:- Status
[INFO]:-PID = 14134
[INFO]:-Configuration reports status as = Up
[INFO]:-Segment status = Up
current role切换回prefered role。
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