一 机器和vip资源

PostgreSQL

pg1: 192.168.56.105

pg2: 192.168.56.106

etcd

etcd: 192.168.56.104

vip

读写vip: 192.168.56.111

二 通过callback脚本实现vip漂移

客户端通过vip的方式访问PostgreSQL数据库可以多一层防护，Patroni支持用户配置在特定事件发生时触发的回调脚本。因此可以配置一个回调，在主备切换后动态加载vip。

加载vip的回调脚本/pgsql/loadvip.sh

pg1和pg2实例如下

[root@localhost ~]# cat /pgsql/loadvip.sh

#!/bin/bash

VIP=192.168.56.111

GATEWAY=192.168.56.1

DEV=enp0s8

action=$1

role=$2

cluster=$3

log()

{

  echo "loadvip: $*"|logger

}

load_vip()

{

ip a|grep -w ${DEV}|grep -w ${VIP} >/dev/null

if [ $? -eq 0 ] ;then

  log "vip exists, skip load vip"

else

  sudo ip addr add ${VIP}/32 dev ${DEV} >/dev/null

  rc=$?

  if [ $rc -ne 0 ] ;then

    log "fail to add vip ${VIP} at dev ${DEV} rc=$rc"

    exit 1

  fi

  log "added vip ${VIP} at dev ${DEV}"

  arping -U -I ${DEV} -s ${VIP} ${GATEWAY} -c 5 >/dev/null

  rc=$?

  if [ $rc -ne 0 ] ;then

    log "fail to call arping to gateway ${GATEWAY} rc=$rc"

    exit 1

  fi

  log "called arping to gateway ${GATEWAY}"

fi

}

unload_vip()

{

ip a|grep -w ${DEV}|grep -w ${VIP} >/dev/null

if [ $? -eq 0 ] ;then

  sudo ip addr del ${VIP}/32 dev ${DEV} >/dev/null

  rc=$?

  if [ $rc -ne 0 ] ;then

    log "fail to delete vip ${VIP} at dev ${DEV} rc=$rc"

    exit 1

  fi

  log "deleted vip ${VIP} at dev ${DEV}"

else

  log "vip not exists, skip delete vip"

fi

}

log "loadvip start args:'$*'"

case $action in

  on_start|on_restart|on_role_change)

    case $role in

      master)

        load_vip

        ;;

      replica)

        unload_vip

        ;;

      *)

        log "wrong role '$role'"

        exit 1

        ;;

    esac

    ;;

  *)

    log "wrong action '$action'"

    exit 1

    ;;

esac

修改patroni配置文件/etc/patroni.yml

pg1和pg2实例配置回调函数

postgresql:

...

  callbacks:

    on_start: /bin/bash /pgsql/loadvip.sh

    on_restart: /bin/bash /pgsql/loadvip.sh

    on_role_change: /bin/bash /pgsql/loadvip.sh

重新加载patroni配置

pg1和pg2实例重新加载配置信息

patronictl reload pgsql

三 vip发生可漂移

主从状态查看

-bash-4.2$ patronictl  list

vip信息查看

执行switchover操作

-bash-4.2$ patronictl switchover

主库vip漂移查看

/var/log/messages系统日志查看

注意：如果直接停止主库上的patroni，vip不会被drop掉。主库上的patroni被停掉后会触发备库failover成为新主库，此时主从2台机器上都有vip，但是由于新主执行了arping，一般不会影响应用访问。