在Azure雲上實現postgres主備切換
阿新 • • 發佈：2019-09-05
以下是工作上實現postgres主備切換功能所用到的程式碼和步驟，中間走了不少彎路，在此記錄下。所用到的作業系統為centos 7.5，安裝了兩臺伺服器，hostname為VM7的為Master，VM8則為Slave。
1、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
其他環境設定
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/=.*$/=disabled/' /etc/selinux/config [root@springcloud-vm7 ~]# setenforce 0 # set timezone [root@springcloud-vm7 ~]# timedatectl set-timezone Asia/Shanghai # postgres⽤使用者環境 [root@springcloud-vm7 ~]# su - postgres -bash-4.2$ vi ~/.bash_profile 。。。 PATH=$PATH:/usr/pgsql-10/bin;export PATH -bash-4.2$ . ~/.bash_profile #注意：~/.bash_profile改後為： PGDATA=/usr/local/pgsql/data PATH=/usr/local/pgsql/bin:$PATH export PGDATA PATH
安裝nginx充當給azure做探測的服務（probe）：
[root@springcloud-vm7 ~]# yum install -y epel-release [root@springcloud-vm7 ~]# yum install -y nginx [root@springcloud-vm7 ~]# vi /etc/nginx/nginx.conf ... listen 5999 default_server; #修改監聽埠在5999上
由於Azure上LB的floatingIP限制，它會將流量量導向probe成功的後端機器器，並且只能有⼀一臺probe成功。
參考官⽅方例例⼦子，它是⽤用iptable來阻⽌止probe：https://github.com/Azure/azure-quickstart-templates/tree/master/haproxy-redundant-floatingip-ubuntu
azure的LSB設定：
注意：負載均衡的probe端⼝口設定成5999，floatingIP設定啟⽤用
2、配置master
[root@springcloud-vm7 ~]# su – postgres
# 建立複製⽤使用者
-bash-4.2$ 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)
# 配置引數
-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
# 重啟
-bash-4.2$ pg_ctl restart
注意：如果是首次安裝，需要在防火牆中開放5432埠
#檢視各埠網路連線情況
[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
3、配置slave
[root@springcloud-vm8 ~]# su – postgres # 直接⽤用repl⽤使用者備份到$PGDATA⽬目錄 -bash-4.2$ rm -rf /var/lib/pgsql/10/data -bash-4.2$ /usr/pgsql-10/bin/pg_basebackup -R -Pv -h vm7 -U repl -D $PGDATA Password: #postgres pg_basebackup: initiating base backup, waiting for checkpoint to complete pg_basebackup: checkpoint completed pg_basebackup: write-ahead log start point: 0/2000028 on timeline 1 pg_basebackup: starting background WAL receiver 24421/24421 kB (100%), 1/1 tablespace pg_basebackup: write-ahead log end point: 0/20000F8 pg_basebackup: waiting for background process to finish streaming ... pg_basebackup: base backup completed # 修改recovery.conf⽂檔案 -bash-4.2$ 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 $PGDATA/arch %r' recovery_target_timeline = 'latest' # 重啟 -bash-4.2$ pg_ctl restart
4、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
5、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 {
[email protected]
}
notification_email_from [email protected]
smtp_server 127.0.0.1
smtp_connect_timeout 30
router_id PG_HA #主備庫需要一致
}
vrrp_script chk_pg_alived {
script "/sbin/ss -ntlp4 | grep :5432 > /dev/null" # 探測端⼝口判斷資料庫存活，1分鐘失敗則認為失敗
interval 10
weight 20
fall 6
}
vrrp_instance VI_1 {
state MASTER # 主庫上填MASTER, 備庫上為BACKUP
interface eth0 # 填寫當前網絡卡名稱，可以用IP Ad命令檢視
virtual_router_id 61
priority 100 #備庫的優先順序設為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，這⾥裡里填本機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時會執⾏行行的指令碼，通過判斷資料庫狀態決定是否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中改為slot_vm8）
#儲存後修改指令碼檔案許可權
[root@springcloud-vm7 keepalived]# chmod 777 master.sh
#切換成slave時會執⾏行行的指令碼
[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中改為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中改為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
#儲存後修改指令碼檔案許可權
[root@springcloud-vm7 keepalived]# chmod 777 backup.sh
6、測試
6.1、 關閉Master伺服器
6.2、 在Slave伺服器中監控keepalived： journalctl -f -u keepalived
6.3、 在Slave伺服器中查詢postgres日誌：tail -fn20 /var/lib/pgsql/10/data/log/postgresql-Tue.log
6.4、 在Slave伺服器中監控IP是否發生了漂移： ip a
6.5、 在Slave伺服器中檢視主備狀態： psql -xc "select pg_is_in_recovery()"
6.6、在Slave伺服器中建立新表：psql -c 'create table t2 (id integer)'
6.7、 Master伺服器啟動後再看主備狀態：psql -xc "select pg_is_in_recovery()"
&n