集群安装信息参考：
系统初始化：http://blog.51cto.com/michaelkang/2167195
集群安装配置：http://blog.51cto.com/michaelkang/2170627
本文对敏感信息进行了替换！！！！
集群主备节点
master => gpnode615.kjh.com
standby => gpnode616.kjh.com状态查看工具 gpstate
命令 参数 作用
gpstate -b =》 显示简要状态
gpstate -c =》 显示主镜像映射
gpstart -d =》 指定数据目录（默认值：$MASTER_DATA_DIRECTORY）
gpstate -e =》 显示具有镜像状态问题的片段
gpstate -f =》 显示备用主机详细信息
gpstate -i =》 显示GRIPLUM数据库版本
gpstate -m =》 显示镜像实例同步状态
gpstate -p =》 显示使用端口
gpstate -Q =》 快速检查主机状态
gpstate -s =》 显示集群详细信息
gpstate -v =》 显示详细信息查看集群备用节点状态
gpstate -f
=>]:-Standby master details
=>]:-----------------------
=>]:- Standby address = gpnode616.kjh.com
=>]:- Standby data directory = /usr/local/gpdata/gpmaster/gpseg-1
=>]:- Standby port = 5432
=>]:- Standby PID = 45634
=>]:- Standby status = Standby host passive
=>]:--------------------------------------------------------------
=>]:--pg_stat_replication
=>]:--------------------------------------------------------------
=>]:--WAL Sender State: streaming
=>]:--Sync state: sync
=>]:--Sent Location: 0/C0006C0
=>]:--Flush Location: 0/C0006C0
=>]:--Replay Location: 0/C0006C0
=>]:--------------------------------------------------------------
以上信息显示standby状态正常！
切换步骤如下：
定义：
master => gpnode615.kjh.com （server1）
standby => gpnode616.kjh.com (server2）
MASTER_DATA_DIRECTORY => /usr/local/gpdata/gpmaster/gpseg-1
模拟master节点故障 （master节点执行）
pg_ctl stop -D $(MASTER_DATA_DIRECTORY)
or
pg_ctl stop -D /usr/local/gpdata/gpmaster/gpseg-1
再次查看standby节点状态
（master节点执行）
$ gpstate -f
=> gpadmin-[INFO]:-Starting gpstate with args: -f
=> gpadmin-[INFO]:-local Greenplum Version: 'postgres (Greenplum Database) 5.10.2 build => '
=> gpadmin-[CRITICAL]:-gpstate failed. (Reason='could not connect to server: Connection refused
Is the server running on host "localhost" (::1) and accepting
TCP/IP connections on port 5432?
could not connect to server: Connection refused
Is the server running on host "localhost" (127.0.0.1) and accepting
TCP/IP connections on port 5432?
') exiting...
集群进入异常状态，无法获取信息；激活备用节点
设置gpadmin账户的环境并使之生效
（standby节点，gpadmin账户操作）
修改.bashrc
su - gpadmin
cat >>/home/gpadmin/.bashrc<<-EOF
source /usr/local/greenplum-db/greenplum_path.sh
export MASTER_DATA_DIRECTORY=/usr/local/gpdata/gpmaster/gpseg-1
export PGPORT=5432
EOF
修改.bash_profile
su - gpadmin
cat >>/home/gpadmin/.bash_profile<<-EOF
source /usr/local/greenplum-db/greenplum_path.sh
export MASTER_DATA_DIRECTORY=/usr/local/gpdata/gpmaster/gpseg-1
export PGPORT=5432
EOF使之生效
source ~/.bashrc
source ~/.bash_profile激活standby节点
（standby节点，gpadmin账户操作）
gpactivatestandby -d /usr/local/gpdata/gpmaster/gpseg-1
=》]:------------------------------------------------------
=》]:-Standby data directory = /usr/local/gpdata/gpmaster/gpseg-1
=》]:-Standby port = 5432
=》]:-Standby running = yes
=》]:-Force standby activation = no
=》]:------------------------------------------------------确认切换：
Do you want to continue with standby master activation? Yy|Nn (default=N):
> y <== !!!初始化输出信息如下：
=》]:-found standby postmaster process
。。。。。。。。。。。。。。。。。
=》]:-Writing the gp_dbid file - /usr/local/gpdata/gpmaster/gpseg-1/gp_dbid...
=》]:-But found an already existing file.
=》]:-Hence removed that existing file.
=》]:-Creating a new file...
=》]:-Wrote dbid: 1 to the file.
=》]:-Now marking it as read only...
=》]:-Verifying the file...
=》]:------------------------------------------------------
=》]:-The activation of the standby master has completed successfully.
=》]:-cndh1322-6-16 is now the new primary master.
=》]:-You will need to update your user access mechanism to reflect
=》]:-the change of master hostname.
=》]:-operational, this could result in database corruption!
=》]:-MASTER_DATA_DIRECTORY is now /usr/local/gpdata/gpmaster/gpseg-1 if
=》]:-this has changed as a result of the standby master activation, remember
=》]:-to change this in any startup scripts etc, that may be configured
=》]:-to set this value.
=》]:-MASTER_PORT is now 5432, if this has changed, you
=》]:-Do not re-start the failed master while the fail-over master is
=》]:-may need to make additional configuration changes to allow access
=》]:-to the Greenplum instance.
。。。。。。。。。。。。再次查看standby节点状态
（standby节点，gpadmin账户操作）
gpstate -f
=>]:-Starting gpstate with args: -f
=>]:-local Greenplum Version: 'postgres (Greenplum Database) 5.10.2 build =>
=>]:-Obtaining Segment details from master...
=>]:-Standby master instance not configured
=>]:--------------------------------------------------------------
=>]:--pg_stat_replication
=>]:--------------------------------------------------------------
=>]:-No entries found.
=>]:--------------------------------------------------------------
集群可以查看状态，无法获取信息备用节点信息，此时集群可以访问；将原有主节点添加为standby （master节点，gpadmin账户操作）
注意这里添加的时候，会check master的数据库目录，要把原master节点的的目录删除或者重命名
mv /usr/local/gpdata/gpmaster/gpseg-1 /usr/local/gpdata/gpmaster/gpseg-1.bak
将原有主节点先添加为standby 节点
（standby节点，gpadmin账户操作）
gpinitstandby -s gpnode615.kjh.com
=>]:-Validating environment and parameters for standby initialization...
=>]:-Checking for filespace directory /usr/local/gpdata/gpmaster/gpseg-1 on gpnode615.kjh.com
=>]:------------------------------------------------------
=>]:-Greenplum standby master initialization parameters
=>]:------------------------------------------------------
=>]:-Greenplum master hostname = gpnode616.kjh.com
=>]:-Greenplum master data directory = /usr/local/gpdata/gpmaster/gpseg-1
=>]:-Greenplum master port = 5432
=>]:-Greenplum standby master hostname = gpnode615.kjh.com
=>]:-Greenplum standby master port = 5432
=>]:-Greenplum standby master data directory = /usr/local/gpdata/gpmaster/gpseg-1
=>]:-Greenplum update system catalog = On
=>]:------------------------------------------------------
=>]:- Filespace locations
=>]:------------------------------------------------------
=>]:-pg_system -> /usr/local/gpdata/gpmaster/gpseg-1
#确认添加从节点
Do you want to continue with standby master initialization? Yy|Nn (default=N):
> y
=>]:-Syncing Greenplum Database extensions to standby
=>]:-The packages on gpnode615.kjh.com are consistent.
=>]:-Adding standby master to catalog...
=>]:-Database catalog updated successfully.
=>]:-Updating pg_hba.conf file...
=>]:-pg_hba.conf files updated successfully.
=>]:-Updating filespace flat files...
=>]:-Filespace flat file updated successfully.
=>]:-Starting standby master
=>]:-Checking if standby master is running on host: gpnode615.kjh.com in directory: /usr/local/gpdata/gpmaster/gpseg-1
=>:-Cleaning up pg_hba.conf backup files...
=>:-Backup files of pg_hba.conf cleaned up successfully.
=>:-Successfully created standby master on gpnode615.kjh.com查看集群备用节点状态
gpstate -f
=》]:-Obtaining Segment details from master...
=》]:-Standby master details
=》]:-----------------------
=》]:- Standby address = gpnode615.kjh.com
=》]:- Standby data directory = /usr/local/gpdata/gpmaster/gpseg-1
=》]:- Standby port = 5432
=》]:- Standby PID = 29968
=》]:- Standby status = Standby host passive
=》]:--------------------------------------------------------------
=》]:--pg_stat_replication
=》]:--------------------------------------------------------------
=》]:--WAL Sender State: streaming
=》]:--Sync state: sync
=》]:--Sent Location: 0/140000A8
=》]:--Flush Location: 0/140000A8
=》]:--Replay Location: 0/140000A8
=》]:--------------------------------------------------------------
以上信息显示新添加 gpnode615.kjh.com standby状态正常！将master 切换至原节点
gpnode615.kjh.com
操作方法按照主备切换方法反向操作即可；
#### 现集群状态：
standby => gpnode615.kjh.com
master => gpnode616.kjh.com
以下操作，按照现集群角色配置！！！
#### 模拟master节点故障
（gpnode616.kjh.com 节点执行）
pg_ctl stop -D /usr/local/gpdata/gpmaster/gpseg-1
#### 激活standby节点
（gpnode615.kjh.com 节点，gpadmin账户操作）
gpactivatestandby -d /usr/local/gpdata/gpmaster/gpseg-1
#### 添加standby
（gpnode616.kjh.com节点，gpadmin账户操作）
注意这里添加的时候，会check master的数据库目录，要把原master节点的的目录删除或者重命名
mv /usr/local/gpdata/gpmaster/gpseg-1 /usr/local/gpdata/gpmaster/gpseg-1.bak
#### 将原有主节点先添加为standby 节点,
（gpnode615.kjh.com节点，gpadmin账户操作）
gpinitstandby -s gpnode616.kjh.com
#### 验证
gpstate -f
Standby address =
Standby data directory = /usr/local/gpdata/gpmaster/gpseg-1
Standby port = 5432
Standby PID = 136489
Standby status = Standby host passive