基于repmgr的postgresql主备高可用方案
- 2019 年 12 月 18 日
- 筆記
本文比较基础，主要介绍postgresql开源高可用工具repmgr的部署和使用，初学者可以根据本文步骤一步一步做下去，废话不多说，直接进入主题，本文以两台机器为例。
1.两台机器分别编译安装postgresql，步骤略。
2.主库配置
vi postgresql.conf wal_log_hints=on archive_mode=on archive_command=’test ! -f /pgarch/%f && cp %p /pgarch/%f’
创建管理用户和库
createuser -s repmgr createdb repmgr -O repmgr vi pg_hba.conf local replication repmgr trust host replication repmgr 127.0.0.1/32 trust host replication repmgr 192.168.1.1/32 trust host replication repmgr 192.168.1.2/32 trust local repmgr repmgr trust host repmgr repmgr 127.0.0.1/32 trust host repmgr repmgr 192.168.1.1/32 trust host repmgr repmgr 192.168.1.2/32 trust
备库连接测试
psql 'host=192.168.1.1 user=repmgr dbname=repmgr connect_timeout=2'
主库创建/etc/repmgr.conf
node_id=1 node_name=node1 conninfo='host=192.168.1.1 user=repmgr dbname=repmgr connect_timeout=2' data_directory='/pgdata'
注册主库
repmgr -f /etc/repmgr.conf primary register
查看：
repmgr -f /etc/repmgr.conf cluster show SELECT * FROM repmgr.nodes;
3.备库配置
创建/etc/repmgr.conf
node_id=2 node_name=node2 conninfo='host=192.168.1.2 user=repmgr dbname=repmgr connect_timeout=2' data_directory='/pgdata'
克隆备库，内部使用的是pg_basebackup来进行克隆，并且会自动创建recovery.conf文件
repmgr -h 192.168.1.1 -U repmgr -d repmgr -f /etc/repmgr.conf standby clone --dry-run repmgr -h 192.168.1.1 -U repmgr -d repmgr -f /etc/repmgr.conf standby clone
启动并注册备库
repmgr -f /etc/repmgr.conf standby register
查看集群状态
repmgr -f /etc/repmgr.conf cluster show [postgres@node2 pgdata]$ repmgr cluster show ID | Name | Role | Status | Upstream | Location | Priority | Timeline | Connection string ----+-------+---------+-----------+----------+----------+----------+----------+--------------------------------------------------------------- 1 | node1 | primary | * running | | default | 100 | 3 | host=192.168.1.1 user=repmgr dbname=repmgr connect_timeout=2 2 | node2 | standby | running | node1 | default | 100 | 3 | host=192.168.1.2 user=repmgr dbname=repmgr connect_timeout=2
查看复制状态
select * from pg_stat_replication; select * from pg_stat_wal_receiver;
切换测试，在备库操作，注意，切换操作需要配置主机间互信。
[postgres@DB2 .ssh]$ repmgr standby switchover NOTICE: executing switchover on node "node2" (ID: 2) NOTICE: local node "node2" (ID: 2) will be promoted to primary; current primary "node1" (ID: 1) will be demoted to standby NOTICE: stopping current primary node "node1" (ID: 1) NOTICE: issuing CHECKPOINT DETAIL: executing server command "pg_ctl -D '/pgdata' -W -m fast stop" INFO: checking for primary shutdown; 1 of 60 attempts ("shutdown_check_timeout") INFO: checking for primary shutdown; 2 of 60 attempts ("shutdown_check_timeout") INFO: checking for primary shutdown; 3 of 60 attempts ("shutdown_check_timeout") NOTICE: current primary has been cleanly shut down at location 0/14000028 NOTICE: promoting standby to primary DETAIL: promoting server "node2" (ID: 2) using "pg_ctl -w -D '/pgdata' promote" waiting for server to promote.... done server promoted NOTICE: waiting up to 60 seconds (parameter "promote_check_timeout") for promotion to complete NOTICE: STANDBY PROMOTE successful DETAIL: server "node2" (ID: 2) was successfully promoted to primary INFO: local node 1 can attach to rejoin target node 2 DETAIL: local node's recovery point: 0/14000028; rejoin target node's fork point: 0/14000098 NOTICE: setting node 1's upstream to node 2 WARNING: unable to ping "host=192.168.1.1 user=repmgr dbname=repmgr connect_timeout=2" DETAIL: PQping() returned "PQPING_NO_RESPONSE" NOTICE: starting server using "pg_ctl -w -D '/pgdata' start" NOTICE: NODE REJOIN successful DETAIL: node 1 is now attached to node 2 NOTICE: switchover was successful DETAIL: node "node2" is now primary and node "node1" is attached as standby NOTICE: STANDBY SWITCHOVER has completed successfully
此时查看状态，已经切换完成：
[postgres@GCCX4TMP .ssh]$ repmgr cluster show ID | Name | Role | Status | Upstream | Location | Priority | Timeline | Connection string ----+-------+---------+-----------+----------+----------+----------+----------+--------------------------------------------------------------- 1 | node1 | standby | running | node2 | default | 100 | 3 | host=192.168.1.1 user=repmgr dbname=repmgr connect_timeout=2 2 | node2 | primary | * running | | default | 100 | 4 | host=192.168.1.2 user=repmgr dbname=repmgr connect_timeout=2
看上面的切换日志其实可以看到切换的一个流程：
①停止主库
②备库promte为主库
③原主库执行rejoin操作：repmgr node rejoin -d 'host=192.168.1.1 dbname=repmgr user=repmgr' –force-rewind –config-files=postgresql.conf,postgresql.auto.conf –verbose
这里说下repmgr node rejoin操作，执行该命令之前先删除recovery.conf文件，并且要求数据库之前是干净的关闭，达到一个一致性状态。然后repmgr会检查数据库能否加入，如果不能的话就会使用pg_rewind进行恢复操作，至于pg_rewind的原理和用法见我上一篇文章。
后面的文章我们再介绍一下如何通过repmgrd实现auto failover。
