以下是工作上实现postgres主备切换功能所用到的代码和步骤，中间走了不少弯路，在此记录下。所用到的操作系统为centos 7.5，安装了两台服务器，hostname为VM7的为Master，VM8则为Slave。
1、安装pg10
vm7（Mater）,vm8（Slave）均需安装:
[root@springcloud-vm7 ~]# yum install –y https://download.postgresql.org/pub/repos/yum/reporpms/EL-7-x86_64/pgdg-redhat-repo-latest.noarch.rpm [root@springcloud-vm7 ~]# yum install postgresql10 -y [root@springcloud-vm7 ~]# yum install postgresql10-server -y [root@springcloud-vm7 ~]# systemctl enable postgresql-10 [root@springcloud-vm7 ~]# /usr/pgsql-10/bin/postgresql-10-setup initdb [root@springcloud-vm7 ~]# systemctl start postgresql-10 [root@springcloud-vm7 ~]# systemctl status postgresql-10
其他环境设置
vm7（Mater）,vm8（Slave）均需安装:
# hosts [root@springcloud-vm7 ~]# vi /etc/hosts ... 10.0.0.14 springcloud-vm7 vm7 10.0.0.15 springcloud-vm8 vm8 # disable selinux [root@springcloud-vm7 ~]# sed -i '7s/=.*$/=disabled/' /etc/selinux/config [root@springcloud-vm7 ~]# setenforce 0 # set timezone [root@springcloud-vm7 ~]# timedatectl set-timezone Asia/Shanghai # postgres⽤用户环境 [root@springcloud-vm7 ~]# su - postgres -bash-4.2$ vi ~/.bash_profile 。。。 PATH=$PATH:/usr/pgsql-10/bin;export PATH -bash-4.2$ . ~/.bash_profile #注意：~/.bash_profile改后为： PGDATA=/usr/local/pgsql/data PATH=/usr/local/pgsql/bin:$PATH export PGDATA PATH
安装nginx充当给azure做探测的服务（probe）：
[root@springcloud-vm7 ~]# yum install -y epel-release [root@springcloud-vm7 ~]# yum install -y nginx [root@springcloud-vm7 ~]# vi /etc/nginx/nginx.conf ... listen 5999 default_server; #修改监听端口在5999上
由于Azure上LB的floatingIP限制，它会将流量量导向probe成功的后端机器器，并且只能有⼀一台probe成功。
参考官⽅方例例⼦子，它是⽤用iptable来阻⽌止probe：https://github.com/Azure/azure-quickstart-templates/tree/master/haproxy-redundant-floatingip-ubuntu
azure的LSB设置：
注意：负载均衡的probe端⼝口设置成5999，floatingIP设置启⽤用
2、配置master
[root@springcloud-vm7 ~]# su – postgres # 创建复制⽤用户 -bash-4.2$ psql -c "create role repl replication login password 'postgres'" # 创建⼀一个slot -bash-4.2$ psql -c "select pg_create_physical_replication_slot('slot_vm7')" pg_create_physical_replication_slot ------------------------------------- (slot_vm7,) (1 row) # 配置参数 -bash-4.2$ cd $PGDATA -bash-4.2$ vi postgresql.conf 。。。 listen_addresses = '*' archive_mode = on archive_command = 'cp -n %p $PGDATA/arch/%f' log_timezone = 'Asia/Shanghai' timezone = 'Asia/Shanghai' 。。。 # 创建arch⽬目录 -bash-4.2$ mkdir $PGDATA/arch/ # 配置pg_hba.conf -bash-4.2$ vi pg_hba.conf 。。。 host replication repl 10.0.0.0/24 md5 # 重启 -bash-4.2$ pg_ctl restart 注意：如果是首次安装，需要在防火墙中开放5432端口 #查看各端口网络连接情况 [root@springcloud-vm7 ~]# netstat –na #安装iptables防火墙 [root@springcloud-vm7 ~]# yum install iptables-services #编辑iptables防火墙配置 [root@springcloud-vm7 ~]# vi /etc/sysconfig/iptables 。。。 -A INPUT -m state --state NEW -m tcp -p tcp --dport 5432 -j ACCEPT
3、配置slave
[root@springcloud-vm8 ~]# su – postgres # 直接⽤用repl⽤用户备份到$PGDATA⽬目录 -bash-4.2$ rm -rf /var/lib/pgsql/10/data -bash-4.2$ /usr/pgsql-10/bin/pg_basebackup -R -Pv -h vm7 -U repl -D $PGDATA Password: #postgres pg_basebackup: initiating base backup, waiting for checkpoint to complete pg_basebackup: checkpoint completed pg_basebackup: write-ahead log start point: 0/2000028 on timeline 1 pg_basebackup: starting background WAL receiver 24421/24421 kB (100%), 1/1 tablespace pg_basebackup: write-ahead log end point: 0/20000F8 pg_basebackup: waiting for background process to finish streaming ... pg_basebackup: base backup completed # 修改recovery.conf⽂文件 -bash-4.2$ vi $PGDATA/recovery.conf standby_mode = 'on' primary_conninfo = 'user=repl password=postgres host=vm7 port=5432 sslmode=prefer sslcompression=1 krbsrvname=postgres target_session_attrs=any' primary_slot_name = 'slot_vm7' restore_command = 'cp $PGDATA/arch/%f %p' archive_cleanup_command = 'pg_archivecleanup $PGDATA/arch %r' recovery_target_timeline = 'latest' # 重启 -bash-4.2$ pg_ctl restart
4、检查
#主库上检查下： -bash-4.2$ psql -xc "select * from pg_stat_replication" -[ RECORD 1 ]----+------------------------------ pid | 90512 usesysid | 16384 usename | repl application_name | walreceiver client_addr | 10.0.0.11 client_hostname | client_port | 44464 backend_start | 2019-07-09 18:36:25.005202+08 backend_xmin | state | streaming sent_lsn | 0/F0004A0 write_lsn | 0/F0004A0 flush_lsn | 0/F0004A0 replay_lsn | 0/F0004A0 write_lag | flush_lag | replay_lag | sync_priority | 0 sync_state | async -bash-4.2$ pg_controldata ... -bash-4.2$ psql -xc "select * from pg_replication_slots" ... #被库上检查： -bash-4.2$ psql -xc "select * from pg_stat_wal_receiver" ... -bash-4.2$ /usr/pgsql-10/bin/pg_controldata ... -bash-4.2$ psql -xc "select pg_is_in_recovery()" -[ RECORD 1 ]-----+-- pg_is_in_recovery | t
5、安装keepalived
vm7（Mater）,vm8（Slave）均需安装:
[root@springcloud-vm7 data]# yum install keepalived -y [root@springcloud-vm7 data]# systemctl enable keepalived [root@springcloud-vm7 data]# systemctl start keepalived [root@springcloud-vm7 data]# cd /etc/keepalived/ [root@springcloud-vm7 ~]# vi /etc/keepalived/keepalived.conf ! Configuration File for keepalived global_defs { notification_email { admin@example.com } notification_email_from pg@example.com smtp_server 127.0.0.1 smtp_connect_timeout 30 router_id PG_HA #主备库需要一致 } vrrp_script chk_pg_alived { script "/sbin/ss -ntlp4 | grep :5432 > /dev/null" # 探测端⼝口判断数据库存活，1分钟失败则认为失败 interval 10 weight 20 fall 6 } vrrp_instance VI_1 { state MASTER # 主库上填MASTER, 备库上为BACKUP interface eth0 # 填写当前网卡名称，可以用IP Ad命令查看 virtual_router_id 61 priority 100 #备库的优先级设为90 advert_int 3 !nopreempt preempt_delay 60 unicast_src_ip 10.0.0.14 # 云主机只能使⽤用单播⽅方式，这⾥里里填本机ip unicast_peer { 10.0.0.15 #另⼀台ip } authentication { auth_type PASS auth_pass 1111 } virtual_ipaddress { 139.217.92.247 #虚拟ip } track_script { chk_pg_alived } notify_master "/etc/keepalived/master.sh" notify_backup "/etc/keepalived/backup.sh" } # 切换成master时会执⾏行行的脚本，通过判断数据库状态决定是否promote [root@springcloud-vm7 keepalived]# vi master.sh #!/bin/bash export PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin # allow probe from azure systemctl restart nginx dbstate=`su - postgres -c "psql -Atc 'select pg_is_in_recovery()'"` if [ $dbstate != "t" ]; then exit 0 fi # promote the slave to master su - postgres -c "/usr/pgsql-10/bin/pg_ctl promote" sleep 5 echo "select pg_create_physical_replication_slot('slot_vm7')" | su – postgres -c "psql" #注意slot的名字主备库要相应修改⼀⼀对应（Slave中改为slot_vm8） #保存后修改脚本文件权限 [root@springcloud-vm7 keepalived]# chmod 777 master.sh #切换成slave时会执⾏行行的脚本 [root@springcloud-vm7 keepalived]# vi backup.sh #!/bin/bash export PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin # block probe from azure systemctl stop nginx # check pg state dbstate=`su - postgres -c "psql -Atc 'select pg_is_in_recovery()'"` if [ $dbstate = "t" ]; then exit 0 fi # change master to slave if [ ! -f /var/lib/pgsql/10/data/recovery.conf ] ; then cat > /var/lib/pgsql/10/data/recovery.conf << EOF standby_mode = 'on' primary_conninfo = 'user=repl password=postgres host=vm8 port=5432 sslmode=prefer sslcompression=1 krbsrvname=postgres target_session_attrs=any' #注意slot的名字主备库要相应修改⼀⼀对应（Slave中改为vm7） primary_slot_name = 'slot_vm8' #注意slot的名字主备库要相应修改⼀⼀对应（Slave中改为slot_vm7） restore_command = 'cp $PGDATA/arch/%f %p' archive_cleanup_command = 'pg_archivecleanup $PGDATA/arch %r' recovery_target_timeline = 'latest' EOF fi sleep 60 su - postgres -c "/usr/pgsql-10/bin/pg_ctl stop" systemctl start postgresql-10 #注意slot的名字主备库要相应修改⼀⼀对应 #保存后修改脚本文件权限 [root@springcloud-vm7 keepalived]# chmod 777 backup.sh
6、测试
6.1、 关闭Master服务器
6.2、 在Slave服务器中监控keepalived： journalctl -f -u keepalived
6.3、 在Slave服务器中查询postgres日志：tail -fn20 /var/lib/pgsql/10/data/log/postgresql-Tue.log
6.4、 在Slave服务器中监控IP是否发生了漂移： ip a
6.5、 在Slave服务器中查看主备状态： psql -xc "select pg_is_in_recovery()"
6.6、在Slave服务器中创建新表：psql -c 'create table t2 (id integer)'
6.7、 Master服务器启动后再看主备状态：psql -xc "select pg_is_in_recovery()"
