本文介绍了如何使用PGPool-II结合PG流复制，搭建双机集群，实现实时读写分离、负载均衡和HA主备切换。详细配置包括：主机规划、SSH密钥配置、pgpool安装、pgpool环境变量、pool_hba.conf、pcp.conf、pgpool.conf的设置，以及主备切换的模拟和数据线同步。通过这种方式，可以在主节点故障时，自动将服务切换到备节点，保证服务不间断。
基于PG的流复制能实现热备切换，但是是要手动建立触发文件实现，对于一些HA场景来说，需要当主机down了后，备机自动切换，经查询资料知道pgpool-II可以实现这种功能。本文基于PG流复制基础上 ，以pgpool-II实现主备切换。在配置pgpool之前需分别在两台规划机上安装好pg数据库，且配置好了流复制环境，关于流复制配置参考前文：http://www.jianshu.com/p/12bc931ebba3。
pgpool双机集群架构图.png
基于PGPool的双机集群如上图所示：pg主节点和备节点实现流复制热备，pgpool1，pgpool2作为中间件，将主备pg节点加入集群，实现读写分离，负载均衡和HA故障自动切换。两pgpool节点可以委托一个虚拟ip节点作为应用程序访问的地址，两节点之间通过watchdog进行监控，当pgpool1宕机时，pgpool2会自动接管虚拟ip继续对外提供不间断服务。
一 主机规划
主机名 | IP | 角色 | 端口
:----:|:----:|:----:|:----:|:----:|:----:
master| 192.168.0.108 |PGMaster|5432
| 192.168.0.108|pgpool1|9999
slave|192.168.0.109|PGSlave|5432
| 192.168.0.109|pgpool2|9999
vip|192.168.0.150|虚拟ip|9999
建立好主机规划之后，在master，slave上两台机器设置下host
[root@localhost ~]# vi .bashrc
#编辑内容如下：
192.168.0.108 master
192.168.0.109 slave
192.168.0.150 vip
二 配置ssh秘钥
在master,slave机器上都生成ssh如下：
[root@localhost ~]# su - postgres
[postgres@localhost ~]$ ssh-keygen -t rsa
[postgres@localhost ~]$ cat ~/.ssh/id_rsa.pub >> ~/.ssh/authorized_keys
[postgres@localhost ~]$ chmod 600 ~/.ssh/authorized_keys
分别将master的公钥复制到slave，slave的公钥复制到master。
#master端
[postgres@localhost ~]$ scp ~/.ssh/authorized_keys postgres@slave:~/.ssh/
#slave端
[postgres@localhost ~]$ scp ~/.ssh/authorized_keys postgres@master:~/.ssh/
验证下ssh配置是否成功
#master端
[postgres@slave ~]$ ssh postgres@slave
Last login: Tue Dec 20 21:22:50 2016 from master
#slave端
[postgres@slave ~]$ ssh postgres@master
Last login: Tue Dec 20 21:22:50 2016 from slave
证明ssh信任关系配置成功。
三 安装pgpool
# 下载pgpool
[root@master opt]# wget http://www.pgpool.net/mediawiki/images/pgpool-II-3.6.0.tar.gz
# 解压
[root@master opt]# tar -zxvf pgpool-II-3.6.0.tar.gz
# 文件权限设置为postgres(其实并非一定装在postgres账户，只不过之前ssh设置都在postgres下，为了方便)
[root@master opt]# chown -R postgres.postgres /opt/pgpool-II-3.6.0
[root@master ~]# su - postgres
[postgres@master opt]$ cd pgpool-II-3.6.0
[postgres@master pgpool-II-3.6.0]$ ./configure –prefix=/opt/pgpool -with-pgsql=path -with-pgsql=/home/postgres
[postgres@master pgpool-II-3.6.0]$ make
[postgres@master pgpool-II-3.6.0]$ make install
安装pgpool相关函数，并非强制，可选安装，为了系统稳定，建议安装
安装pg_reclass,pg_recovery
[postgres@master pgpool-II-3.6.0]$ cd src/sql
[postgres@master sql]$ make
[postgres@master sql]$ make install
[postgres@master sql]$ psql -f insert_lock.sql
安装全部结束。
四 配置pgpool
4.1 配置pgpool环境变量
pgpool装在了postgres账户下，在该账户中添加环境变量，master,slave节点都执行。
[postgres@master ~]$ cd /home/postgres
[postgres@master ~]$ vim .bashrc
#编辑内容如下
PGPOOLHOME=/opt/pgpool
export PGPOOLHOME
PATH=$PATH:$HOME/.local/bin:$HOME/bin:$PGHOME/bin:$PGPOOLHOME/bin
export PATH
4.2 配置pool_hba.conf
pool_hba.conf是对登录用户进行验证的，要和pg的pg_hba.conf保持一致，要么都是trust，要么都是md5验证方式，这里采用了md5验证方式如下设置：
[postgres@master ~]$ cd /opt/pgpool/etc
[postgres@etc~]$ cp pool_hba.conf.sample pool_hba.conf
[postgres@etc~]$ vim pool_hba.conf
#编辑内容如下
# "local" is for Unix domain socket connections only
local all all md5
# IPv4 local connections:
host all all 0.0.0.0/0 md5
host all all 0/0 md5
4.3 配置pcp.conf
pcp.conf配置用于pgpool自己登陆管理使用的，一些操作pgpool的工具会要求提供密码等，配置如下：
[postgres@master ~]$ cd /opt/pgpool/etc
[postgres@etc~]$ cp pcp.conf.sample pcp.conf
# 使用pg_md5生成配置的用户名密码
[postgres@etc~]$ pg_md5 nariadmin
6b07583ba8af8e03043a1163147faf6a
#pcp.conf是pgpool管理器自己的用户名和密码，用于管理集群。
[postgres@etc~]$ vim pcp.conf
#编辑内容如下
postgres:6b07583ba8af8e03043a1163147faf6a
#保存退出！
#在pgpool中添加pg数据库的用户名和密码
[postgres@etc~]$ pg_md5 -p -m -u postgres pool_passwd
#数据库登录用户是postgres,这里输入登录密码，不能出错
#输入密码后，在pgpool/etc目录下会生成一个pool_passwd文件
4.4 配置系统命令权限
配置 ifconfig, arping 执行权限 ，执行failover_stream.sh需要用到，可以让其他普通用户执行。
[root@master ~]# chmod u+s /sbin/ifconfig
[root@master ~]# chmod u+s /usr/sbin
4.5 配置pgpool.conf
查看本机网卡，配置后面的delegate_IP需要
[postgres@etc~]$ ifconfig
网卡名称.png
配置master上的pgpool.conf:
[postgres@master ~]$ cd /opt/pgpool/etc
[postgres@etc~]$ cp pgpool.conf.sample pgpool.conf
[postgres@etc~]$ vim pgpool.conf
编辑内容如下：
# CONNECTIONS
listen_addresses = '*'
port = 9999
pcp_listen_addresses = '*'
pcp_port = 9898
# - Backend Connection Settings -
backend_hostname0 = 'master'
backend_port0 = 5432
backend_weight0 = 1
backend_data_directory0 = '/home/postgres/data'
backend_flag0 = 'ALLOW_TO_FAILOVER'
backend_hostname1 = 'slave'
backend_port1 = 5432
backend_weight1 = 1
backend_data_directory1 = '/home/postgres/data'
backend_flag1 = 'ALLOW_TO_FAILOVER'
# - Authentication -
enable_pool_hba = on
pool_passwd = 'pool_passwd'
# FILE LOCATIONS
pid_file_name = '/opt/pgpool/pgpool.pid'
replication_mode = off
load_balance_mode = on
master_slave_mode = on
master_slave_sub_mode = 'stream'
sr_check_period = 5
sr_check_user = 'repuser'
sr_check_password = 'repuser'
sr_check_database = 'postgres'
#------------------------------------------------------------------------------
# HEALTH CHECK 健康检查
#------------------------------------------------------------------------------
health_check_period = 10 # Health check period
# Disabled (0) by default
health_check_timeout = 20
# Health check timeout
# 0 means no timeout
health_check_user = 'postgres'
# Health check user
health_check_password = 'nariadmin' #数据库密码
# Password for health check user
health_check_database = 'postgres'
#必须设置，否则primary数据库down了，pgpool不知道，不能及时切换。从库流复制还在连接数据，报连接失败。
#只有下次使用pgpool登录时，发现连接不上，然后报错，这时候，才知道挂了，pgpool进行切换。
#主备切换的命令行配置
#------------------------------------------------------------------------------
# FAILOVER AND FAILBACK
#------------------------------------------------------------------------------
failover_command = '/opt/pgpool/failover_stream.sh %H '
#------------------------------------------------------------------------------
# WATCHDOG
#------------------------------------------------------------------------------
# - Enabling -
use_watchdog = on
# - Watchdog communication Settings -
wd_hostname = 'master'
# Host name or IP address of this watchdog
# (change requires restart)
wd_port = 9000
# port number for watchdog service
# (change requires restart)
# - Virtual IP control Setting -
delegate_IP = 'vip'
# delegate IP address
# If this is empty, virtual IP never bring up.
# (change requires restart)
if_cmd_path = '/sbin'
# path to the directory where if_up/down_cmd exists
# (change requires restart)
if_up_cmd = 'ifconfig eth1:0 inet $_IP_$ netmask 255.255.255.0'
# startup delegate IP command
# (change requires restart)
# eth1根据现场机器改掉
if_down_cmd = 'ifconfig eth1:0 down'
# shutdown delegate IP command
# (change requires restart)
# eth1根据现场机器改掉
# -- heartbeat mode --
wd_heartbeat_port = 9694
# Port number for receiving heartbeat signal
# (change requires restart)
wd_heartbeat_keepalive = 2
# Interval time of sending heartbeat signal (sec)
# (change requires restart)
wd_heartbeat_deadtime = 30
# Deadtime interval for heartbeat signal (sec)
# (change requires restart)
heartbeat_destination0 = 'slave'
# Host name or IP address of destination 0
# for sending heartbeat signal.
# (change requires restart)
heartbeat_destination_port0 = 9694
# Port number of destination 0 for sending
# heartbeat signal. Usually this is the
# same as wd_heartbeat_port.
# (change requires restart)
heartbeat_device0 = 'eth1'
# Name of NIC device (such like 'eth0')
# used for sending/receiving heartbeat
# signal to/from destination 0.
# This works only when this is not empty
# and pgpool has root privilege.
# (change requires restart)
# eth1根据现场机器改掉
# - Other pgpool Connection Settings -
other_pgpool_hostname0 = 'slave' #对端
# Host name or IP address to connect to for other pgpool 0
# (change requires restart)
other_pgpool_port0 = 9999
# Port number for othet pgpool 0
# (change requires restart)
other_wd_port0 = 9000
# Port number for othet watchdog 0
# (change requires restart)
配置slave上的pgpool.conf:
# CONNECTIONS
listen_addresses = '*'
port = 9999
pcp_listen_addresses = '*'
pcp_port = 9898
# - Backend Connection Settings -
backend_hostname0 = 'master'
backend_port0 = 5432
backend_weight0 = 1
backend_data_directory0 = '/home/postgres/data'
backend_flag0 = 'ALLOW_TO_FAILOVER'
backend_hostname1 = 'slave'
backend_port1 = 5432
backend_weight1 = 1
backend_data_directory1 = '/home/postgres/data'
backend_flag1 = 'ALLOW_TO_FAILOVER'
# - Authentication -
enable_pool_hba = on
pool_passwd = 'pool_passwd'
# FILE LOCATIONS
pid_file_name = '/opt/pgpool/pgpool.pid'
replication_mode = off
load_balance_mode = on
master_slave_mode = on
master_slave_sub_mode = 'stream'
sr_check_period = 5
sr_check_user = 'repuser'
sr_check_password = 'repuser'
sr_check_database = 'postgres'
#------------------------------------------------------------------------------
# HEALTH CHECK 健康检查
#------------------------------------------------------------------------------
health_check_period = 10 # Health check period
# Disabled (0) by default
health_check_timeout = 20
# Health check timeout
# 0 means no timeout
health_check_user = 'postgres'
# Health check user
health_check_password = 'nariadmin' #数据库密码
# Password for health check user
health_check_database = 'postgres'
#必须设置，否则primary数据库down了，pgpool不知道，不能及时切换。从库流复制还在连接数据，报连接失败。
#只有下次使用pgpool登录时，发现连接不上，然后报错，这时候，才知道挂了，pgpool进行切换。
#主备切换的命令行配置
#------------------------------------------------------------------------------
# FAILOVER AND FAILBACK
#------------------------------------------------------------------------------
failover_command = '/opt/pgpool/failover_stream.sh %H '
#------------------------------------------------------------------------------
# WATCHDOG
#------------------------------------------------------------------------------
# - Enabling -
use_watchdog = on
# - Watchdog communication Settings -
wd_hostname = 'slave' #本端
# Host name or IP address of this watchdog
# (change requires restart)
wd_port = 9000
# port number for watchdog service
# (change requires restart)
# - Virtual IP control Setting -
delegate_IP = 'vip'
# delegate IP address
# If this is empty, virtual IP never bring up.
# (change requires restart)
if_cmd_path = '/sbin'
# path to the directory where if_up/down_cmd exists
# (change requires restart)
if_up_cmd = 'ifconfig eth1:0 inet $_IP_$ netmask 255.255.255.0'
# startup delegate IP command
# (change requires restart)
# eth1根据现场机器改掉
if_down_cmd = 'ifconfig eth1:0 down'
# shutdown delegate IP command
# (change requires restart)
# eth1根据现场机器改掉
# -- heartbeat mode --
wd_heartbeat_port = 9694
# Port number for receiving heartbeat signal
# (change requires restart)
wd_heartbeat_keepalive = 2
# Interval time of sending heartbeat signal (sec)
# (change requires restart)
wd_heartbeat_deadtime = 30
# Deadtime interval for heartbeat signal (sec)
# (change requires restart)
heartbeat_destination0 = 'master' #对端
# Host name or IP address of destination 0
# for sending heartbeat signal.
# (change requires restart)
heartbeat_destination_port0 = 9694
# Port number of destination 0 for sending
# heartbeat signal. Usually this is the
# same as wd_heartbeat_port.
# (change requires restart)
heartbeat_device0 = 'eth1'
# Name of NIC device (such like 'eth0')
# used for sending/receiving heartbeat
# signal to/from destination 0.
# This works only when this is not empty
# and pgpool has root privilege.
# (change requires restart)
# eth1根据现场机器改掉
# - Other pgpool Connection Settings -
other_pgpool_hostname0 = 'master' #对端
# Host name or IP address to connect to for other pgpool 0
# (change requires restart)
other_pgpool_port0 = 9999
# Port number for othet pgpool 0
# (change requires restart)
other_wd_port0 = 9000
# Port number for othet watchdog 0
# (change requires restart)
配置文件里，故障处理配置的是failover_command = '/opt/pgpool/failover_stream.sh %H '，因此，需要在/opt/pgpool目录中写个failover_stream.sh脚本：
[postgres@master ~]$ cd /opt/pgpool
[postgres@pgpool~]$ touch failover_stream.sh
[postgres@pgpool~]$ vim failover_stream.sh
注意这里使用了promote 而不是触发文件，触发文件来回切换有问题，编辑内容如下：
#! /bin/sh
# Failover command for streaming replication.
# Arguments: $1: new master hostname.
new_master=$1
trigger_command="$PGHOME/bin/pg_ctl promote -D $PGDATA"
# Prompte standby database.
/usr/bin/ssh -T $new_master $trigger_command
exit 0;
如果是其他用户创建的，需要赋予postgres可执行权限，例如
[root@opt ~]$ chown -R postgres.postgres /opt/pgpool
[root@opt ~]]$ chmod 777 /opt/pgpool/failover_stream.sh
五 PGPool集群管理
启动之前在master,slave节点创建两个日志文件：
[root@master ~]# mkdir /var/log/pgpool
[root@master ~]# chown -R postgres.postgres /var/log/pgpool
[root@master ~]# mkdir /var/run/pgpool
[root@master ~]# chown -R postgres.postgres /var/run/pgpool
5.1 启动集群
分别启动primary,standby的pg库
#master上操作
[postgres@master ~]$ pg_ctl start -D $PGDATA
#slave上操作
[postgres@slave ~]$ pg_ctl start -D $PGDATA
分别启动pgpool命令：
#master上操作
# -D会重新加载pg nodes的状态如down或up
[postgres@master ~]$ pgpool -n -d -D > /var/log/pgpool/pgpool.log 2>&1 &
[1] 3557
#slave上操作
[postgres@slave ~]$ pgpool -n -d -D > /var/log/pgpool/pgpool.log 2>&1 &
[1] 3557
注意快速终止pgpool命令：
[postgres@ ~]$ pgpool -m fast stop
启动pgpool后，查看集群节点状态:
[postgres@master ~]$ psql -h vip -p 9999
psql (9.6.1)
#提示输入密码：
Type "help" for help.
postgres=# show pool_nodes;
node_id | hostname | port | status | lb_weight | role | select_cnt | load_balance_node | replication_delay
---------+----------+------+--------+-----------+---------+------------+-------------------+-------------------
0 | master | 5432 | up | 0.500000 | primary | 0 | false | 0
1 | slave | 5432 | up | 0.500000 | standby | 0 | true | 0
(2 rows)
#在slave上节点也是psql -h vip -p 9999，双pgpool使用虚拟ip，做到高可用。
发现当前主备节点都是正常的up状态。
5.2 Pgpool的HA
5.2.1 模拟master端pgpool宕机
在master节点上停止pgpool服务
[postgres@master ~]$ pgpool -m fast stop
#稍等片刻后，访问集群
[postgres@master ~]$ psql -h vip -p 9999
psql (9.6.1)
#提示输入密码：
Type "help" for help.
postgres=# show pool_nodes;
node_id | hostname | port | status | lb_weight | role | select_cnt | load_balance_node | replication_delay
---------+----------+------+--------+-----------+---------+------------+-------------------+-------------------
0 | master | 5432 | up | 0.500000 | primary | 0 | false | 0
1 | slave | 5432 | up | 0.500000 | standby | 0 | true | 0
(2 rows)
#访问成功，在master节点上的pgpool宕机后，由slave节点的pgpool接管vip和集群服务，并未中断应用访问。
#在master上重新启动pgpool后，定制slave上的pgpool服务，结果一样。
5.2.2模拟master端pg primary宕机
[postgres@master ~]$ pg_ctl stop
#master端打印
2017-07-24 18:52:37.751 PDT [28154] STATEMENT: SELECT pg_current_xlog_location()
2017-07-24 18:52:37.760 PDT [2553] LOG: received fast shutdown request
2017-07-24 18:52:37.760 PDT [2553] LOG: aborting any active transactions
2017-07-24 18:52:37.762 PDT [28156] FATAL: canceling authentication due to timeout
2017-07-24 18:52:37.763 PDT [2555] LOG: shutting down
2017-07-24 18:52:37.768 PDT [28158] FATAL: the database system is shutting down
2017-07-24 18:52:37.775 PDT [28159] FATAL: the database system is shutting down
2017-07-24 18:52:39.653 PDT [2553] LOG: database system is shut down
#slave端打印
2017-07-24 18:52:41.455 PDT [2614] LOG: invalid record length at 0/2A000098: wanted 24, got 0
2017-07-24 18:52:47.333 PDT [2614] LOG: received promote request
2017-07-24 18:52:47.333 PDT [2614] LOG: redo done at 0/2A000028
2017-07-24 18:52:47.333 PDT [2614] LOG: last completed transaction was at log time 2017-07-24 18:17:00.946759-07
2017-07-24 18:52:47.336 PDT [2614] LOG: selected new timeline ID: 10
2017-07-24 18:52:47.841 PDT [2614] LOG: archive recovery complete
2017-07-24 18:52:47.851 PDT [2613] LOG: database system is ready to accept connections
#日志清楚看到主机down机了，slave切换了。
#稍等片刻后，访问集群
[postgres@master ~]$ psql -h vip -p 9999
Password:
psql (10beta1)
Type "help" for help.
postgres=# show pool_nodes;
node_id | hostname | port | status | lb_weight | role | select_cnt | load_balance_node | replication_delay
---------+----------+------+--------+-----------+---------+------------+-------------------+-------------------
0 | master | 5432 | down | 0.500000 | standby | 0 | false | 0
1 | slave | 5432 | up | 0.500000 | primary | 0 | true | 0
(2 rows)
#slave已经被切换成primary，且master节点状态是down
5.2.3 修复master节点重新加入集群
master节点down机后，slave节点已经被切换成了primary，修复好master后应重新加入节点，作为primary的standby。
修复master端并启动操作：
[postgres@master ~]$ cd $PGDATA
[postgres@master data]$ mv recovery.done recovery.conf #一定要把.done改成.conf
[postgres@master data]$ pg_ctl start
在pgpool集群中加入节点状态:
#注意master的node_id是0，所以-n 0
[postgres@master data]$ pcp_attach_node -d -U postgres -h vip -p 9898 -n 0
#提示输入密码，输入pcp管理密码。
#查看当前状态
postgres=# show pool_nodes;
node_id | hostname | port | status | lb_weight | role | select_cnt | load_balance_node | replication_delay
---------+----------+------+--------+-----------+---------+------------+-------------------+-------------------
0 | master | 5432 | up | 0.500000 | standby | 0 | false | 0
1 | slave | 5432 | up | 0.500000 | primary | 0 | true | 0
(2 rows)
5.2.4 主机直接down机
当前slave节点是primay，我们直接将slave服务器直接关机后，发现实现了主备切换，slave已经down了，而master已经被切换成了primary：
[postgres@master ~]$ psql -h vip -p 9999
Password:
psql (10beta1)
Type "help" for help.
postgres=# show pool_nodes;
node_id | hostname | port | status | lb_weight | role | select_cnt | load_balance_node | replication_delay
---------+----------+------+--------+-----------+---------+------------+-------------------+-------------------
0 | master | 5432 | up | 0.500000 | primary | 0 | true | 0
1 | slave | 5432 | down | 0.500000 | standby | 0 | false | 0
(2 rows)
5.3 数据线同步
在主备切换时，修复节点并重启后，由于primary数据发生变化，或修复的节点数据发生变化再按照流复制模式加入集群，很可能报时间线不同步错误：
#slave机器重启后，由于master或slave数据不同步产生了
[postgres@slave data]$ mv recovery.done recovery.conf
[postgres@slave data]$ pg_ctl start
waiting for server to start....2017-07-24 19:31:44.563 PDT [2663] LOG: listening on IPv4 address "0.0.0.0", port 5432
2017-07-24 19:31:44.563 PDT [2663] LOG: listening on IPv6 address "::", port 5432
2017-07-24 19:31:44.565 PDT [2663] LOG: listening on Unix socket "/tmp/.s.PGSQL.5432"
2017-07-24 19:31:44.584 PDT [2664] LOG: database system was shut down at 2017-07-24 19:31:30 PDT
2017-07-24 19:31:44.618 PDT [2664] LOG: entering standby mode
2017-07-24 19:31:44.772 PDT [2664] LOG: consistent recovery state reached at 0/2D000098
2017-07-24 19:31:44.772 PDT [2663] LOG: database system is ready to accept read only connections
2017-07-24 19:31:44.772 PDT [2664] LOG: invalid record length at 0/2D000098: wanted 24, got 0
2017-07-24 19:31:44.798 PDT [2668] LOG: fetching timeline history file for timeline 11 from primary server
2017-07-24 19:31:44.826 PDT [2668] FATAL: could not start WAL streaming: ERROR: requested starting point 0/2D000000 on timeline 10 is not in this server's history
DETAIL: This server's history forked from timeline 10 at 0/2B0001B0.
2017-07-24 19:31:44.826 PDT [2664] LOG: new timeline 11 forked off current database system timeline 10 before current recovery point 0/2D000098
done
产生这种情况，需要根据pg_rewind工具同步数据时间线，具体分5步走。
5.3.1停掉需要做同步的节点pg服务
[postgres@slave ] pg_ctl stop
5.3.2 同步master节点上时间线
[postgres@slave data]$ pg_rewind --target-pgdata=/home/postgres/data --source-server='host=master port=5432 user=postgres dbname=postgres password=nariadmin'
servers diverged at WAL location 0/2B0001B0 on timeline 10
rewinding from last common checkpoint at 0/2B000108 on timeline 10
Done!
5.3.3 修改pg_hba.conf与 recovery.done文件
#pg_hba.conf与 recovery.done都是同步master上来的，要改成slave自己的
[postgres@slave ] cd $PGDATA
[postgres@slave data]$ mv recovery.done recovery.conf
[postgres@slave data]$ vi pg_hba.conf
#slave改成master(相当于slave的流复制对端)
host replication repuser master md5
[postgres@slave data]$ vi recovery.conf
#slave改成master(相当于slave的流复制对端)
primary_conninfo = 'host=master port=5432 user=repuser password=repuser'
5.3.4 重启pg服务
[postgres@slave data]$ pg_ctl start
waiting for server to start....2017-07-24 19:47:06.821 PDT [2722] LOG: listening on IPv4 address "0.0.0.0", port 5432
2017-07-24 19:47:06.821 PDT [2722] LOG: listening on IPv6 address "::", port 5432
2017-07-24 19:47:06.907 PDT [2722] LOG: listening on Unix socket "/tmp/.s.PGSQL.5432"
2017-07-24 19:47:06.930 PDT [2723] LOG: database system was interrupted while in recovery at log time 2017-07-24 19:25:42 PDT
2017-07-24 19:47:06.930 PDT [2723] HINT: If this has occurred more than once some data might be corrupted and you might need to choose an earlier recovery target.
2017-07-24 19:47:06.961 PDT [2723] LOG: entering standby mode
2017-07-24 19:47:06.966 PDT [2723] LOG: redo starts at 0/2B0000D0
2017-07-24 19:47:06.971 PDT [2723] LOG: consistent recovery state reached at 0/2B01CA30
2017-07-24 19:47:06.972 PDT [2722] LOG: database system is ready to accept read only connections
2017-07-24 19:47:06.972 PDT [2723] LOG: invalid record length at 0/2B01CA30: wanted 24, got 0
2017-07-24 19:47:06.982 PDT [2727] LOG: started streaming WAL from primary at 0/2B000000 on timeline 11
done
server started
5.3.5 重新加入集群
#注意slave的node_id是1，所以-n 1
[postgres@slave data]$ pcp_attach_node -d -U postgres -h vip -p 9898 -n 1
Password: #提示输入密码，输入pcp管理密码。
DEBUG: recv: tos="m", len=8
DEBUG: recv: tos="r", len=21
DEBUG: send: tos="C", len=6
DEBUG: recv: tos="c", len=20
pcp_attach_node -- Command Successful
DEBUG: send: tos="X", len=4
5.3.6 查看集群节点状态
[postgres@slave data]$ psql -h vip -p 9999
Password:
psql (10beta1)
Type "help" for help.
postgres=# show pool_nodes;
node_id | hostname | port | status | lb_weight | role | select_cnt | load_balance_node | replication_delay
---------+----------+------+--------+-----------+---------+------------+-------------------+-------------------
0 | master | 5432 | up | 0.500000 | primary | 0 | true | 0
1 | slave | 5432 | up | 0.500000 | standby | 0 | false | 0
(2 rows)
全部恢复工作完成。
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