PostgreSQL高可用之repmgr（1主2从+1witness）+Pgpool-II实现主从切换+读写分离
【摘要】 一、总体架构 二、环境申请 三、配置4台主机之间的互信 四、配置repmgr 4.1、主库修改pg_hba.conf参数文件 4.2、主库修改postgresql.conf参数文件 4.3、主库创建相关用户和数据库 4.4、4个节点分别修改repmgr.conf 4.5、在主库注册主库服务 4.6、克隆备库1和备库2 4.6.1、4个节点都配~/.pgpass密码文件 4.6.2、克隆备库...
一、总体架构
本文最终需要实现的目标：
1、1主2从流复制
2、读写分离+负载均衡（pgpool-II）
3、主从自动切换（repmgr）
所有的节点：安装操作系统、创建PG用户目录、安装PG软件、安装repmgr
主库：只初始化主库、启动主库归档
二、环境申请
先申请4台机器，6.66节点最后再申请，反正docker容器都是即开即用的。
-- 主库
docker rm -f lhrrepmgr64361
docker run -d --name lhrrepmgr64361 -h lhrrepmgr64361 \
--net=pg-network --ip 172.72.6.61 \
-p 64361:5432 \
-v /sys/fs/cgroup:/sys/fs/cgroup \
--privileged=true lhrbest/lhrpgall:1.0 \
/usr/sbin/init
docker network connect bridge lhrrepmgr64361
-- 从库1
docker rm -f lhrrepmgr64362
docker run -d --name lhrrepmgr64362 -h lhrrepmgr64362 \
--net=pg-network --ip 172.72.6.62 \
-p 64362:5432 \
-v /sys/fs/cgroup:/sys/fs/cgroup \
--privileged=true lhrbest/lhrpgall:1.0 \
/usr/sbin/init
docker network connect bridge lhrrepmgr64362
-- 从库2
docker rm -f lhrrepmgr64363
docker run -d --name lhrrepmgr64363 -h lhrrepmgr64363 \
--net=pg-network --ip 172.72.6.63 \
-p 64363:5432 \
-v /sys/fs/cgroup:/sys/fs/cgroup \
--privileged=true lhrbest/lhrpgall:1.0 \
/usr/sbin/init
docker network connect bridge lhrrepmgr64363
-- Witness库
docker rm -f lhrrepmgr64364
docker run -d --name lhrrepmgr64364 -h lhrrepmgr64364 \
--net=pg-network --ip 172.72.6.64 \
-p 64364:5432 \
-v /sys/fs/cgroup:/sys/fs/cgroup \
--privileged=true lhrbest/lhrpgall:1.0 \
/usr/sbin/init
docker network connect bridge lhrrepmgr64364
-- 重启4台机器
docker restart lhrrepmgr64361 lhrrepmgr64362 lhrrepmgr64363 lhrrepmgr64364
[root@docker35 ~]# docker ps | grep repmgr
31d3d31c1073 lhrbest/lhrpgall:1.0 "/usr/sbin/init" 41 hours ago Up 41 hours 5433-5435/tcp, 0.0.0.0:64364->5432/tcp lhrrepmgr64364
572d4ea2c072 lhrbest/lhrpgall:1.0 "/usr/sbin/init" 41 hours ago Up 41 hours 5433-5435/tcp, 0.0.0.0:64363->5432/tcp lhrrepmgr64363
6ded416b2016 lhrbest/lhrpgall:1.0 "/usr/sbin/init" 41 hours ago Up 41 hours 5433-5435/tcp, 0.0.0.0:64362->5432/tcp lhrrepmgr64362
fa38b58b8f3d lhrbest/lhrpgall:1.0 "/usr/sbin/init" 41 hours ago Up 41 hours 5433-5435/tcp, 0.0.0.0:64361->5432/tcp lhrrepmgr64361
[root@docker35 ~]#
👉 注意：
1、镜像lhrbest/lhrpgall:1.0中，申请的4台主机均已安装好PG 13和repmgr软件
2、PG安装方式为编译安装，数据库已初始化完成，用户为pg13
3、该镜像里已安装了PG13、PG12、PG11、PG10和PG9.6这几个版本，均为编译安装，本文使用PG13来操作
三、配置4台主机之间的互信
-- 只在主库61节点上，以root用户执行：
chmod +x sshUserSetup.sh
./sshUserSetup.sh -user pg13 -hosts "172.72.6.61 172.72.6.62 172.72.6.63 172.72.6.64" -advanced exverify -confirm
-- 在每台主机修改权限，否则报错：Bad owner or permissions on /home/pg13/.ssh/config
chmod 600 /home/pg13/.ssh/config
依次输入：yes，回车和密码即可。
脚本下载：https://share.weiyun.com/57HUxNi
验证：
ssh pg13@lhrrepmgr64361 date
ssh pg13@lhrrepmgr64362 date
ssh pg13@lhrrepmgr64363 date
ssh pg13@lhrrepmgr64364 date
第二次执行时不再提示输入yes，并且可以成功执行命令，则表示SSH对等性配置成功。
执行过程：
[pg13@lhrrepmgr64361 /]# ssh pg13@lhrrepmgr64362 date
Tue Apr 27 17:15:04 CST 2021
[root@lhrrepmgr64361 /]#
[pg13@lhrrepmgr64361 /]# ssh pg13@lhrrepmgr64363 date
Tue Apr 27 17:15:08 CST 2021
[root@lhrrepmgr64361 /]#
[pg13@lhrrepmgr64361 /]# ssh pg13@lhrrepmgr64364 date
Tue Apr 27 17:15:13 CST 2021
[pg13@lhrrepmgr64361 /]#
四、配置repmgr
4.1、主库修改pg_hba.conf参数文件
-- 进入主库
docker exec -it lhrrepmgr64361 bash
su - pg13
cat >> /pg13/pgdata/pg_hba.conf <<"EOF"
local repmgr repmgr md5
host repmgr repmgr 127.0.0.1/32 md5
host repmgr repmgr 172.72.6.0/24 md5
local replication repmgr md5
host replication repmgr 127.0.0.1/32 md5
host replication repmgr 172.72.6.0/24 md5
EOF
4.2、主库修改postgresql.conf参数文件
-- 修改参数
cat >> /pg13/pgdata/postgresql.conf <<"EOF"
# 归档参数
wal_level='replica'
archive_mode='on'
archive_command='test ! -f /pg13/archive/%f && cp %p /pg13/archive/%f'
restore_command='cp /pg13/archive/%f %p'
# 主从流复制
hot_standby=on
max_wal_senders=10
wal_sender_timeout=60s
wal_keep_size=16MB
# 主从切换参数，启用PG数据库的复制槽，PG12不需要"use_replication_slots=true"这个参数了。
max_replication_slots=10
wal_log_hints=on
# 自动切换
shared_preload_libraries ='repmgr'
EOF
-- 重启
pg_ctl start
-- 查询
psql -U postgres -h 192.168.66.35 -p 64361
select * from pg_settings where name in ('wal_level','archive_mode','archive_command');
-- 切换归档
select pg_switch_wal();
4.3、主库创建相关用户和数据库
-- 创建相关用户和数据库
su - pg13
createuser -s repmgr
createdb repmgr -O repmgr
psql -h 127.0.0.1 -c "alter user repmgr with password 'lhr';"
psql -h 127.0.0.1 -c "alter user repmgr set search_path to repmgr, \"\$user\",public;"
结果：
[root@lhrrepmgr64361 /]# systemctl start pg13
[root@lhrrepmgr64361 /]# systemctl status pg13
● pg13.service - PostgreSQL database server
Loaded: loaded (/etc/systemd/system/pg13.service; disabled; vendor preset: disabled)
Active: active (running) since Tue 2021-04-27 16:25:24 CST; 6s ago
Docs: man:postgres(1)
Process: 769 ExecStart=/pg13/pg13/bin/pg_ctl start -D ${PGDATA} -s -o -p ${PGPORT} -w -t 300 (code=exited, status=0/SUCCESS)
Main PID: 771 (postgres)
CGroup: /docker/a777ef12d5ff83a9d47be51a98531bd45b42d2b008f7a25f894f3244ce9cc0d4/system.slice/pg13.service
├─771 /pg13/pg13/bin/postgres -D /pg13/pgdata -p 5432
├─772 postgres: logger
├─774 postgres: checkpointer
├─775 postgres: background writer
├─776 postgres: walwriter
├─777 postgres: autovacuum launcher
├─778 postgres: stats collector
└─779 postgres: logical replication launcher
Apr 27 16:25:23 lhrrepmgr64361 systemd[1]: Starting PostgreSQL database server...
Apr 27 16:25:24 lhrrepmgr64361 pg_ctl[769]: 2021-04-27 16:25:24.024 CST [771] LOG: redirecting log output to logging collector process
Apr 27 16:25:24 lhrrepmgr64361 pg_ctl[769]: 2021-04-27 16:25:24.024 CST [771] HINT: Future log output will appear in directory "pg_log".
Apr 27 16:25:24 lhrrepmgr64361 systemd[1]: Started PostgreSQL database server.
[root@lhrrepmgr64361 /]# su - pg13
Last login: Tue Apr 27 16:24:50 CST 2021 on pts/0
[pg13@lhrrepmgr64361 ~]$
[pg13@lhrrepmgr64361 ~]$ createuser -s repmgr
[pg13@lhrrepmgr64361 ~]$
[pg13@lhrrepmgr64361 ~]$ createdb repmgr -O repmgr
[pg13@lhrrepmgr64361 ~]$
[pg13@lhrrepmgr64361 ~]$ psql -h 127.0.0.1 -c "alter user repmgr with password 'lhr'"
ALTER ROLE
[pg13@lhrrepmgr64361 ~]$
[pg13@lhrrepmgr64361 ~]$ psql -h 127.0.0.1 -c "alter user repmgr set search_path to repmgr, \"\$user\",public";
ALTER ROLE
C:\Users\lhrxxt>psql -U postgres -h 192.168.66.35 -p 64361
Password for user postgres:
psql (13.2)
Type "help" for help.
postgres=# \du
List of roles
Role name | Attributes | Member of
-----------+------------------------------------------------------------+-----------
postgres | Superuser, Create role, Create DB, Replication, Bypass RLS | {}
repmgr | Superuser, Create role, Create DB | {}
postgres=# \l
List of databases
Name | Owner | Encoding | Collate | Ctype | Access privileges
-----------+----------+----------+------------+------------+-----------------------
postgres | postgres | UTF8 | en_US.utf8 | en_US.utf8 |
repmgr | repmgr | UTF8 | en_US.utf8 | en_US.utf8 |
template0 | postgres | UTF8 | en_US.utf8 | en_US.utf8 | =c/postgres +
| | | | | postgres=CTc/postgres
template1 | postgres | UTF8 | en_US.utf8 | en_US.utf8 | =c/postgres +
| | | | | postgres=CTc/postgres
(4 rows)
4.4、4个节点分别修改repmgr.conf
-- 以pg13用户修改
su - pg13
-- 主库
cat > /pg13/pg13/repmgr.conf << "EOF"
node_id=1
node_name=lhrrepmgr64361
conninfo='host=172.72.6.61 user=repmgr password=lhr dbname=repmgr connect_timeout=2'
data_directory='/pg13/pgdata'
pg_bindir='/pg13/pg13/bin'
EOF
-- 从库1
cat > /pg13/pg13/repmgr.conf << "EOF"
node_id=2
node_name=lhrrepmgr64362
conninfo='host=172.72.6.62 user=repmgr password=lhr dbname=repmgr connect_timeout=2'
data_directory='/pg13/pgdata'
pg_bindir='/pg13/pg13/bin'
EOF
-- 从库2
cat > /pg13/pg13/repmgr.conf << "EOF"
node_id=3
node_name=lhrrepmgr64363
conninfo='host=172.72.6.63 user=repmgr password=lhr dbname=repmgr connect_timeout=2'
data_directory='/pg13/pgdata'
pg_bindir='/pg13/pg13/bin'
EOF
-- witness节点
cat > /pg13/pg13/repmgr.conf << "EOF"
node_id=4
node_name=lhrrepmgr64364
conninfo='host=172.72.6.64 user=repmgr password=lhr dbname=repmgr connect_timeout=2'
data_directory='/pg13/pgdata'
pg_bindir='/pg13/pg13/bin'
EOF
-- 测试
psql 'host=172.72.6.61 user=repmgr password=lhr dbname=repmgr connect_timeout=2'
psql 'host=172.72.6.62 user=repmgr password=lhr dbname=repmgr connect_timeout=2'
psql 'host=172.72.6.63 user=repmgr password=lhr dbname=repmgr connect_timeout=2'
psql 'host=172.72.6.64 user=repmgr password=lhr dbname=repmgr connect_timeout=2'
4.5、在主库注册主库服务
-- 注册服务
repmgr -f /pg13/pg13/repmgr.conf primary register
-- 查询
repmgr -f /pg13/pg13/repmgr.conf cluster show
psql -U repmgr -h 192.168.66.35 -p 64361 -d repmgr
执行过程：
[pg13@lhrrepmgr64361 pg13]$ repmgr -f /pg13/pg13/repmgr.conf primary register
INFO: connecting to primary database...
NOTICE: attempting to install extension "repmgr"
NOTICE: "repmgr" extension successfully installed
NOTICE: primary node record (ID: 1) registered
[pg13@lhrrepmgr64361 pg13]$
[pg13@lhrrepmgr64361 pg13]$ repmgr -f /pg13/pg13/repmgr.conf cluster show
ID | Name | Role | Status | Upstream | Location | Priority | Timeline | Connection string
----+----------------+---------+-----------+----------+----------+----------+----------+---------------------------------------------------------------------------
1 | lhrrepmgr64361 | primary | * running | | default | 100 | 1 | host=172.72.6.61 user=repmgr password=lhr dbname=repmgr connect_timeout=2
C:\Users\lhrxxt>psql -U repmgr -h 192.168.66.35 -p 64361 -d repmgr
Password for user repmgr:
psql (13.2)
Type "help" for help.
repmgr=# select * from repmgr.nodes;
node_id | upstream_node_id | active | node_name | type | location | priority | conninfo | repluser | slot_name | config_file
---------+------------------+--------+----------------+---------+----------+----------+---------------------------------------------------------------------------+----------+-----------+------------------------
1 | | t | lhrrepmgr64361 | primary | default | 100 | host=172.72.6.61 user=repmgr password=lhr dbname=repmgr connect_timeout=2 | repmgr | | /pg13/pg13/repmgr.conf
(1 row)
4.6、克隆备库1和备库2
4.6.1、4个节点都配~/.pgpass密码文件
su - pg13
echo "*:*:*:repmgr:lhr" > ~/.pgpass
chmod 0600 ~/.pgpass
-- 测试，若不需要密码，那就证明配置正确
psql 'host=172.72.6.61 user=repmgr dbname=repmgr connect_timeout=2'
psql 'host=172.72.6.62 user=repmgr dbname=repmgr connect_timeout=2'
psql 'host=172.72.6.63 user=repmgr dbname=repmgr connect_timeout=2'
psql 'host=172.72.6.64 user=repmgr dbname=repmgr connect_timeout=2'
4.6.2、克隆备库1
-- 其中--dry-run表示不真实执行克隆过程，只是检查是否有问题
repmgr -h 172.72.6.61 -U repmgr -d repmgr -f /pg13/pg13/repmgr.conf standby clone --force --dry-run
-- 执行克隆命令，其实还是调用pg_basebackup
repmgr -h 172.72.6.61 -U repmgr -d repmgr -f /pg13/pg13/repmgr.conf standby clone --force
-- 启动
pg_ctl -D /pg13/pgdata start
-- 查询
psql
select * from pg_stat_wal_receiver;
执行过程：
[pg13@lhrrepmgr64362 ~]$ repmgr -h 172.72.6.61 -U repmgr -d repmgr -f /pg13/pg13/repmgr.conf standby clone --force --dry-run
NOTICE: destination directory "/pg13/pgdata" provided
INFO: connecting to source node
DETAIL: connection string is: host=172.72.6.61 user=repmgr dbname=repmgr
DETAIL: current installation size is 29 MB
INFO: "repmgr" extension is installed in database "repmgr"
WARNING: target data directory appears to be a PostgreSQL data directory
DETAIL: target data directory is "/pg13/pgdata"
HINT: use -F/--force to overwrite the existing data directory
INFO: replication slot usage not requested; no replication slot will be set up for this standby
INFO: parameter "max_wal_senders" set to 10
NOTICE: checking for available walsenders on the source node (2 required)
INFO: sufficient walsenders available on the source node
DETAIL: 2 required, 10 available
NOTICE: checking replication connections can be made to the source server (2 required)
INFO: required number of replication connections could be made to the source server
DETAIL: 2 replication connections required
WARNING: data checksums are not enabled and "wal_log_hints" is "off"
DETAIL: pg_rewind requires "wal_log_hints" to be enabled
NOTICE: standby will attach to upstream node 1
HINT: consider using the -c/--fast-checkpoint option
INFO: all prerequisites for "standby clone" are met
[pg13@lhrrepmgr64362 ~]$ repmgrrepmgr -h 172.72.6.61 -U repmgr -d repmgr -f /pg13/pg13/repmgr.conf standby clone^C
[pg13@lhrrepmgr64362 ~]$ repmgr -h 172.72.6.61 -U repmgr -d repmgr -f /pg13/pg13/repmgr.conf standby clone
NOTICE: destination directory "/pg13/pgdata" provided
INFO: connecting to source node
DETAIL: connection string is: host=172.72.6.61 user=repmgr dbname=repmgr
DETAIL: current installation size is 29 MB
ERROR: target data directory appears to be a PostgreSQL data directory
DETAIL: target data directory is "/pg13/pgdata"
HINT: use -F/--force to overwrite the existing data directory
[pg13@lhrrepmgr64362 ~]$ repmgr -h 172.72.6.61 -U repmgr -d repmgr -f /pg13/pg13/repmgr.conf standby clone --force
NOTICE: destination directory "/pg13/pgdata" provided
INFO: connecting to source node
DETAIL: connection string is: host=172.72.6.61 user=repmgr dbname=repmgr
DETAIL: current installation size is 29 MB
INFO: replication slot usage not requested; no replication slot will be set up for this standby
NOTICE: checking for available walsenders on the source node (2 required)
NOTICE: checking replication connections can be made to the source server (2 required)
WARNING: data checksums are not enabled and "wal_log_hints" is "off"
DETAIL: pg_rewind requires "wal_log_hints" to be enabled
WARNING: directory "/pg13/pgdata" exists but is not empty
NOTICE: -F/--force provided - deleting existing data directory "/pg13/pgdata"
NOTICE: starting backup (using pg_basebackup)...
HINT: this may take some time; consider using the -c/--fast-checkpoint option
INFO: executing:
/pg13/pg13/bin/pg_basebackup -l "repmgr base backup" -D /pg13/pgdata -h 172.72.6.61 -p 5432 -U repmgr -X stream
Password:
WARNING: skipping special file "./.s.PGSQL.5432"
WARNING: skipping special file "./.s.PGSQL.5432"
NOTICE: standby clone (using pg_basebackup) complete
NOTICE: you can now start your PostgreSQL server
HINT: for example: pg_ctl -D /pg13/pgdata start
HINT: after starting the server, you need to register this standby with "repmgr standby register"
[pg13@lhrrepmgr64362 ~]$ pg_ctl -D /pg13/pgdata start
waiting for server to start....2021-04-27 19:14:08.750 CST [9298] LOG: redirecting log output to logging collector process
2021-04-27 19:14:08.750 CST [9298] HINT: Future log output will appear in directory "pg_log".
done
server started
[pg13@lhrrepmgr64362 ~]$ psql
psql (13.2)
Type "help" for help.
postgres=# select * from pg_stat_wal_receiver;
pid | status | receive_start_lsn | receive_start_tli | written_lsn | flushed_lsn | received_tli | last_msg_send_time | last_msg_receipt_time | latest_end_lsn | latest_end_time | slot_name | sender_host | sender_port | conninfo
------+-----------+-------------------+-------------------+-------------+-------------+--------------+-------------------------------+-------------------------------+----------------+-------------------------------+-----------+-------------+-------------+-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
9304 | streaming | 0/3000000 | 1 | 0/30001F0 | 0/30001F0 | 1 | 2021-04-27 19:15:08.862599+08 | 2021-04-27 19:15:08.862719+08 | 0/30001F0 | 2021-04-27 19:14:08.830865+08 | | 172.72.6.61 | 5432 | user=repmgr password=******** channel_binding=disable connect_timeout=2 dbname=replication host=172.72.6.61 port=5432 application_name=lhrrepmgr64362 fallback_application_name=walreceiver sslmode=disable sslcompression=0 ssl_min_protocol_version=TLSv1.2 gssencmode=disable krbsrvname=postgres target_session_attrs=any
(1 row)
信息“NOTICE: standby clone (using pg_basebackup) complete”表示测试完成。
八、总结
1、由于主从切换需要启动数据库，所以，在整个环境中，所有的PG数据库均不能使用systemctl来管理，否则切换会出现问题。
2、若要清除节点的注册信息，也可以进入主库中，操作repmgr.nodes表信息。
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