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主机与IP：
192.168.11.177 主库
192.168.11.180 备库
192.168.11.210 VIP
系统：
centos7.2
PGSQL9.6主从已安装配置完成（参考我之前的博客）
安装配置：
1、安装配置keepalived
主备安装：
# yum install -y keepalived
主配置：
# vi /etc/keepalived/keepalived.conf
bal_defs {
smtp_server 127.0.0.1
smtp_connect_timeout 30
router_id pg
}
vrrp_script chk_pgsql {
script "/etc/keepalived/scripts/pgsql_check.sh"
interval 2
weight -5
fall 2
rise 1
}
vrrp_instance VI_1 {
state BACKUP
interface eth0
virtual_router_id 61
priority 100
nopreempt
advert_int 1
authentication {
auth_type PASS
auth_pass 1111
}
track_script {
chk_pgsql
}
virtual_ipaddress {
192.168.11.210
}
}
备配置：
# vi /etc/keepalived/keepalived.conf
bal_defs {
smtp_server 127.0.0.1
smtp_connect_timeout 30
router_id pg
}
vrrp_script chk_pgsql {
script "/etc/keepalived/scripts/pgsql_check.sh"
interval 2
weight -5
fall 2
rise 1
}
vrrp_instance VI_1 {
state BACKUP
interface eth0
virtual_router_id 61
priority 80
nopreempt
advert_int 1
authentication {
auth_type PASS
auth_pass 1111
}
track_script {
chk_pgsql
}
virtual_ipaddress {
192.168.11.210
}
}
注意：
这里virtual_router_id按照默认的值51会出错bogus VRRP packet received on eth0 !!!，所以改值为61。
主备创建目录和脚本
# mkdir /etc/keepalived/scripts
# vi /etc/keepalived/scripts/pgsql_check.sh
#!/bin/bash
#判断pg是否活着
A=`ps -C postgres --no-header | wc -l`
#判断vip浮到哪里
B=`ip a | grep 192.168.11.210 | wc -l`
#判断是否是从库处于等待的状态
C=`ps -ef | grep postgres | grep 'startup process' | wc -l`
#判断从库链接主库是否正常
D=`ps -ef | grep postgres | grep 'receiver' | wc -l`
#判断主库连接从库是否正常
E=`ps -ef | grep postgres | grep 'sender' | wc -l`
#如果pg死了，将消息写入日记并且关闭keepalived
if [ $A -eq 0 ];then
echo "`date "+%Y-%m-%d--%H:%M:%S"` postgresql stop so vip stop " >> /etc/keepalived/log/check_pg.log
systemctl stop keepalived
else
#判断出主挂了，vip浮到了从，提升从的地位让他可读写
if [ $B -eq 1 -a $C -eq 1 -a $D -eq 0 ];then
su - postgres -c "pg_ctl promote -D /data/pg_data"
echo "`date "+%Y-%m-%d--%H:%M:%S"` standby promote " >> /etc/keepalived/log/check_pg.log
fi
#判断出自己是主并且和从失去联系
if [ $B -eq 1 -a $C -eq 0 -a $D -eq 0 -a $E -eq 0 ];then
sleep 10
echo "`date "+%Y-%m-%d--%H:%M:%S"` can't find standby " >> /etc/keepalived/log/check_pg.log
fi
fi
主备配置日志：
修改 /etc/sysconfig/keepalived
把KEEPALIVED_OPTIONS="-D" 修改为KEEPALIVED_OPTIONS="-D -d -S 0"
# vi /etc/rsyslog.conf
加入如下配置：
#keepalived -S 0
local0.*/var/log/keepalived.log
主备启动服务
# systemctl start keepalived.service
# systemctl enable keepalived.service
2、停止主库服务，并切换主库为备库
停止主库服务，之后发现主库上的VIP消失，备库上的VIP生成，备库变为主库，可以进行建库建表等操作。
原来的主库切换为备库：
$ cd /data/pg_data
$ rm -rf *
$ pg_basebackup -h 192.168.11.180 -U repuser -D /data/pg_data -X stream -P
$ mv recovery.done recovery.conf
$ vi recovery.conf
primary_conninfo = 'host=192.168.11.177 port=5432 user=repuser password=password123! keepalives_idle=60'
>>
primary_conninfo = 'host=192.168.11.180 port=5432 user=repuser password=password123! keepalives_idle=60'
启动主机keepalived
# systemctl start keepalived
3、检查验证
查看原来备库服务和库状态
$ ps -ef | grep postgres
postgres 1081 1 0 Aug07 ? 00:00:06 /usr/local/postgresql/bin/postgres -D /data/pg_data
postgres 1083 1081 0 Aug07 ? 00:00:01 postgres: checkpointer process
postgres 1084 1081 0 Aug07 ? 00:00:02 postgres: writer process
postgres 1085 1081 0 Aug07 ? 00:00:00 postgres: stats collector process
postgres 13961 1081 0 11:09 ? 00:00:00 postgres: wal writer process
postgres 13962 1081 0 11:09 ? 00:00:00 postgres: autovacuum launcher process
postgres 13963 1081 0 11:09 ? 00:00:00 postgres: archiver process last was 000000020000000000000010
postgres 27065 1081 0 11:25 ? 00:00:00 postgres: wal sender process repuser 192.168.11.177(47074) streaming 0/11000060
root 27922 3590 0 11:26 pts/1 00:00:00 grep --color=auto postgres
postgres=# SELECT pg_is_in_recovery from pg_is_in_recovery();
pg_is_in_recovery
-------------------
f
(1 row)
查看原来主库服务和库状态
$ ps -ef | grep postgres
postgres 2602 1 0 11:25 pts/1 00:00:00 /usr/local/postgresql/bin/postgres -D /data/pg_data
postgres 2603 2602 0 11:25 ? 00:00:00 postgres: startup process recovering 000000020000000000000011
postgres 2604 2602 0 11:25 ? 00:00:00 postgres: checkpointer process
postgres 2605 2602 0 11:25 ? 00:00:00 postgres: writer process
postgres 2606 2602 0 11:25 ? 00:00:00 postgres: stats collector process
postgres 2607 2602 0 11:25 ? 00:00:00 postgres: wal receiver process streaming 0/11000060
postgres 2613 2325 0 11:25 pts/1 00:00:00 grep --color=auto postgres
postgres=# SELECT pg_is_in_recovery from pg_is_in_recovery();
pg_is_in_recovery
-------------------
t
(1 row)
4、测试结果
PGSQL高可用测试结果如下：
高可用方案：
PGSQL 主从 + keepalived
资源：
192.168.11.177 主库（称为服务器A）
192.168.11.180 备库 (称为服务器B）
192.168.11.210 VIP
1)、模拟A的PGSQL服务停止
B接管VIP（自动）
B由从库变为主库（自动）
启动A的PGSQL服务，并把A配置为备库（手动）
2)、模拟B的PGSQL服务停止
A接管VIP（自动）
A由从库变为主库（自动）
启动B的PGSQL服务，并把B配置为备库（手动）
参考：
https://blog.csdn.net/vanilla_he/article/details/79001890
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