在Azure雲上實現postgres主備切換

　　如下是工做上實現postgres主備切換功能所用到的代碼和步驟，中間走了很多彎路，在此記錄下。所用到的操做系統爲centos 7.5，安裝了兩臺服務器，hostname爲VM7的爲Master，VM8則爲Slave。

 

　　一、安裝pg10

　　vm7（Mater）,vm8（Slave）均需安裝:

[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

　

　　其餘環境設置

　　vm7（Mater）,vm8（Slave）均需安裝:

# 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⽤用戶環境
[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改後爲：
PGDATA=/usr/local/pgsql/data
PATH=/usr/local/pgsql/bin:$PATH
export PGDATA PATH

 

　　安裝nginx充當給azure作探測的服務（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;   #修改監聽端口在5999上

 

　　因爲Azure上LB的floatingIP限制，它會將流量量導向probe成功的後端機器器，而且只能有⼀一臺probe成功。

　　參考官⽅方例例⼦子，它是⽤用iptable來阻⽌止probe：https://github.com/Azure/azure-quickstart-templates/tree/master/haproxy-redundant-floatingip-ubuntu

 

　　azure的LSB設置：

　　注意：負載均衡的probe端⼝口設置成5999，floatingIP設置啓⽤用

 

　　二、配置master

[root@springcloud-vm7 ~]# su – postgres

# 建立複製⽤用戶
-bash-4.2$ psql -c "create role repl replication login password 'postgres'"

# 建立⼀一個slot
-bash-4.2$ psql -c "select pg_create_physical_replication_slot('slot_vm7')"

pg_create_physical_replication_slot
-------------------------------------
(slot_vm7,)
(1 row)

# 配置參數
-bash-4.2$ cd $PGDATA
-bash-4.2$ vi postgresql.conf
。。。
listen_addresses = '*'
archive_mode = on
archive_command = 'cp -n %p $PGDATA/arch/%f'
log_timezone = 'Asia/Shanghai'
timezone = 'Asia/Shanghai'
。。。
# 建立arch⽬目錄
-bash-4.2$ mkdir $PGDATA/arch/

# 配置pg_hba.conf
-bash-4.2$ vi pg_hba.conf
。。。
host replication repl 10.0.0.0/24 md5

# 重啓
-bash-4.2$ pg_ctl restart


注意：若是是首次安裝，須要在防火牆中開放5432端口
#查看各端口網絡鏈接狀況
[root@springcloud-vm7 ~]# netstat –na

#安裝iptables防火牆
[root@springcloud-vm7 ~]# yum install iptables-services 

#編輯iptables防火牆配置
[root@springcloud-vm7 ~]# vi /etc/sysconfig/iptables 
。。。
-A INPUT -m state --state NEW -m tcp -p tcp --dport 5432 -j ACCEPT

 

　　三、配置slave

 [root@springcloud-vm8 ~]# su – postgres

# 直接⽤用repl⽤用戶備份到$PGDATA⽬目錄
-bash-4.2$ 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'

# 重啓
-bash-4.2$ pg_ctl restart

 

　　四、檢查

#主庫上檢查下：
-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"
...

#被庫上檢查：
-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

 

　　五、安裝keepalived

　　vm7（Mater）,vm8（Slave）均需安裝:

[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     #主備庫須要一致
}

vrrp_script chk_pg_alived {
script "/sbin/ss -ntlp4 | grep :5432 > /dev/null" # 探測端⼝口判斷數據庫存活，1分鐘失敗則認爲失敗
interval 10
weight 20
fall 6
}

vrrp_instance VI_1 {
state MASTER # 主庫上填MASTER, 備庫上爲BACKUP
interface eth0  # 填寫當前網卡名稱，能夠用IP Ad命令查看
virtual_router_id 61
priority 100 #備庫的優先級設爲90
advert_int 3
!nopreempt
preempt_delay 60
unicast_src_ip 10.0.0.14 # 雲主機只能使⽤用單播⽅方式，這⾥裏里填本機ip
unicast_peer {
10.0.0.15 #另⼀臺ip
}

authentication {
auth_type PASS
auth_pass 1111
}

virtual_ipaddress {
139.217.92.247  #虛擬ip
}

track_script {
chk_pg_alived
}

notify_master "/etc/keepalived/master.sh"
notify_backup "/etc/keepalived/backup.sh"
}

# 切換成master時會執⾏行行的腳本，經過判斷數據庫狀態決定是否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的名字主備庫要相應修改⼀⼀對應（Slave中改成slot_vm8）


#保存後修改腳本文件權限
[root@springcloud-vm7 keepalived]# chmod 777 master.sh

#切換成slave時會執⾏行行的腳本
[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的名字主備庫要相應修改⼀⼀對應（Slave中改成vm7）
primary_slot_name = 'slot_vm8' #注意slot的名字主備庫要相應修改⼀⼀對應（Slave中改成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的名字主備庫要相應修改⼀⼀對應

#保存後修改腳本文件權限
[root@springcloud-vm7 keepalived]# chmod 777 backup.sh

 

　　六、測試

　　6.一、  關閉Master服務器

 

 

　　6.二、 在Slave服務器中監控keepalived：  journalctl -f -u keepalived

 

　　6.三、  在Slave服務器中查詢postgres日誌：tail -fn20 /var/lib/pgsql/10/data/log/postgresql-Tue.log

 

　　6.四、 在Slave服務器中監控IP是否發生了漂移： ip a

 

 

　　6.五、  在Slave服務器中查看主備狀態：  psql -xc "select pg_is_in_recovery()"

  

 

　　6.六、在Slave服務器中建立新表：psql -c 'create table t2 (id integer)'

 

 

　　6.七、  Master服務器啓動後再看主備狀態：psql -xc "select pg_is_in_recovery()"