自从PostgreSQL的内置复制机制在9.0中引入以来，repmgr就为其提供了高级支持。当前的repmgr系列repmgr 5支持PostgreSQL 9.3以及后续版本的主从复制，如级联复制、时间线切换和通过复制协议进行基础备份。
2.1 编译安装
tar -zxvf repmgr-5.4.1.tar.gz
chown -R postgres:postgres /tmp/repmgr-5.4.1
su - postgres
cd /tmp/repmgr-5.4.1
./configure make install
验证安装成功：
repmgr --help
2.2 修改配置文件
node_id=1
node_name='pg1'
conninfo='host=pg1 user=repmgr dbname=repmgr connect_timeout=2'
data_directory='/postgres/pgdata'
failover=automatic
promote_command='/postgres/pgsql-16/bin/repmgr standby promote -f etc/repmgr/repmgr.conf --log-to-file'
follow_command='/postgres/pgsql-16/bin/repmgr standby follow -f /etc/repmgr/repmgr.conf --log-to-file --upstream-node-id=%n'
service_start_command = 'pg_ctl start'
service_stop_command = 'pg_ctl stop'
service_restart_command = 'pg_ctl restart'
service_reload_command = 'pg_ctl reload -D /postgres/pgdata'
repmgrd_pid_file='/tmp/repmgrd.pid'
log_file='/tmp/repmgrd.log'
priority=100
2.3 注册数据库
repmgr primary register -f /etc/repmgr/repmgr.conf
repmgr standby register -f /etc/repmgr/repmgr.conf
2.4 查看集群节点状态
[postgres@pg2 ~]$ repmgr cluster show -f /etc/repmgr/repmgr.conf --verbose
NOTICE: using provided configuration file "/etc/repmgr/repmgr.conf"
INFO: connecting to database
ID | Name | Role | Status | Upstream | Location | Priority | Timeline | Connection string
----+------+---------+-----------+----------+----------+----------+----------+-----------------------------------------------------------------
1 | pg1 | primary | * running | | default | 100 | 1 | host=192.168.XXX.130 user=repmgr dbname=repmgr connect_timeout=2
2 | pg2 | standby | running | pg1 | default | 100 | 1 | host=192.168.XXX.131 user=repmgr dbname=repmgr connect_timeout=2
可以看到数据库的node ID、节点名称、节点角色（主/从）、状态和连接串等信息。
[postgres@pg2 ~]$ repmgr cluster show -f /etc/repmgr/repmgr.conf --verbose
NOTICE: using provided configuration file "/etc/repmgr/repmgr.conf"
INFO: connecting to database ERROR: connection to database failed DETAIL: connection to server at "192.168.XXX.130", port 5432 failed: Connection refused Is the server running on that host and accepting TCP/IP connections?
DETAIL: attempted to connect using: user=repmgr connect_timeout=2 dbname=repmgr host=192.168.XXX.130 fallback_application_name=repmgr options=-csearch_path=
ID | Name | Role | Status | Upstream | Location | Priority | Timeline | Connection string
----+------+---------+-----------+----------+----------+----------+----------+-----------------------------------------------------------------
1 | pg1 | primary | - failed | ? | default | 100 | | host=192.168.XXX.130 user=repmgr dbname=repmgr connect_timeout=2 2 | pg2 | primary | * running | | default | 100 | 2 |
host=192.168.XXX.131 user=repmgr dbname=repmgr connect_timeout=2 WARNING: following issues were detected - when attempting to connect to node "pg1" (ID: 1),
following error encountered : "connection to server at "192.168.XXX.130", port 5432 failed: Connection refused Is the server running on that host and accepting TCP/IP connections?"
4.1 测试不执行
/postgres/pgsql-16/bin/repmgr -h pg1 -U repmgr -d repmgr -f /etc/repmgr/repmgr.conf standby clone --dry-run
4.2 执行克隆操作
/postgres/pgsql-16/bin/repmgr -h pg1 -U repmgr -d repmgr -f /etc/repmgr/repmgr.conf standby clone
4.3 注册从库到集群
repmgr standby register -f /etc/repmgr/repmgr.conf
本文作者：高 强(上海新炬中北团队）
本文来源：“IT那活儿”公众号
