基于repmgr的postgresql主备高可用方案

数据库架构之美

修改于 2019-12-27 20:10:28

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修改于 2019-12-27 20:10:28

文章被收录于专栏：数据库架构之美

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。