PostgreSQL使用repmgr配置级联复制

最近的项目要求配置共享存储的四节点集群,使集群能够形成负载均衡。

 

但是大家知道,PostgreSQL不支持使用同一数据目录生成多个实例,在执行pg_ctl start的时候,如果指定的数据目录有实例在运行,则该实例会发生错误导致数据库down掉。故而,我们选择了基于pgpool-II + repmgr的策略来实现基于NAS共享存储的负载均衡策略。架构如下图所示:

 

PostgreSQL使用repmgr配置级联复制_第1张图片

 

共享磁盘的实现方法多种多样,本文主要讲解repmgr的使用方法:

 

(零)准备工作

本例中,准备了四台虚拟机,IP地址分别为:

192.168.100.1 node1

192.168.100.2 node2

192.168.100.3 node3

192.168.100.4 node4

NAS存储中,分别创建目录data1、data2、data3、data4,并挂载到各数据节点上。*注意目录权限必须为700

 

 

在所有节点安装repmgr。其中,只有node1节点上执行initdb,而node2、node3、node4均不初始化

 

在node1节点的postgresql.conf添加以下配置:

hot_standby = on
wal_level = 'replica'
max_wal_senders = 50

 

 

创建repmgr用户及数据库

[Harvest@node1 ~] createuser -s repmgr
[Harvest@node1 ~] createdb repmgr -O repmgr

 

配置pg_hba.conf,添加以下规则:

local    replication     repmgr                                              trust
host     replication     repmgr                 127.0.0.1/32                 trust
host     replication     repmgr                 192.168.100.0/0              trust
local    repmgr          repmgr                                              trust
host     repmgr          repmgr                 127.0.0.1/32                 trust
host     repmgr          repmgr                 192.168.100.0/0              trust

 

启动数据库,并在node2(或node3、node4)测试是否可以通过repmgr连接到数据库

[Harvest@node1 ~] pg_ctl start

[Harvest@node2 ~] psql 'host=node1 user=repmgr dbname=repmgr connect_timeout=2'

 

 

(一)安装repmgr

首先,解压repmgr并安装:

[Harvest@node1 opt]cd repmgr-x.x.x
[Harvest@node1 repmgr-x.x.x] ./configure && make && make install #执行configure的时候需要sed和pg_config两个应用,基本上linux系统都会自带sed,pg_config安装了postgresql也都会有

 

(二)配置node1

在node1上创建配置文件repmgr1.conf:

 node_id=1
 node_name=node1
 conninfo='host=node1 user=repmgr dbname=repmgr connect_timeout=2'
 data_directory='/opt/data/data1' 

 

接下来将node1注册为主服务器:

[Harvest@node1 ~] repmgr -f repmgr1.conf primary register

如果屏幕中回显如下,则注册成功:

INFO: connecting to primary database...
NOTICE: attempting to install extension "repmgr"
NOTICE: "repmgr" extension successfully installed
NOTICE: primary node record (id: 1) registered
 

验证集群状态

[Harvest@node1 ~]repmgr -f repmgr.conf cluster show

回显如下:

  ID | Name  | Role    | Status    | Upstream | Connection string
 ----+-------+---------+-----------+----------+--------------------------------------------------------
  1  | node1 | primary | * running |          | host=node1 dbname=repmgr user=repmgr connect_timeout=2

 

(二)添加node2

如上所述配置repmgr2.conf:

 node_id=2
 node_name=node2
 conninfo='host=node2 user=repmgr dbname=repmgr connect_timeout=2'
 data_directory='/opt/data/data2' 

 

创建node2备份,该步骤会使用pg_basebackup命令将node1节点的数据目录备份到data2目录中

[Harvest@node2 ~] repmgr -h node1 -U repmgr -d repmgr -f repmgr.conf standby clone

回显如下所示说明备份成功

 NOTICE: using configuration file "/etc/repmgr.conf"
 NOTICE: destination directory "/opt/data/data2" provided
 INFO: connecting to source node
 NOTICE: checking for available walsenders on source node (2 required)
 INFO: sufficient walsenders available on source node (2 required)
 INFO: creating directory "/opt/data/data2"...
 NOTICE: starting backup (using pg_basebackup)...
 HINT: this may take some time; consider using the -c/--fast-checkpoint option
 INFO: executing:
      pg_basebackup -l "repmgr base backup" -D /opt/data/data2 -h node1 -U repmgr -X stream
 NOTICE: standby clone (using pg_basebackup) complete
 NOTICE: you can now start your PostgreSQL server
 HINT: for example: pg_ctl -D /opt/data/data2 start

注册node2

[Harvest@node2 ~] repmgr -f repmgr.conf standby register

回显如下:

NOTICE: standby node "node2" (ID: 2) successfully registered

验证集群状态

[Harvest@node1 ~]repmgr -f repmgr.conf cluster show
     ID | Name  | Role    | Status    | Upstream | Location | Connection string
    ----+-------+---------+-----------+----------+----------+--------------------------------------
     1  | node1 | primary | * running |          | default  | host=node1 dbname=repmgr user=repmgr
     2  | node2 | standby |   running | node1    | default  | host=node2 dbname=repmgr user=repmgr

 

(三)注册node3、node4

node3、node4在配置上与node2相同,唯一的区别在于增加了'--upstream-node-id=2'这个参数,它指定了数据流的来源:

[Harvest@node3 ~] repmgr -h node2 -U repmgr -d repmgr -f /etc/repmgr.conf standby clone --upstream-node-id=2
[Harvest@node3 ~] repmgr -f /etc/repmgr.conf standby register --upstream-node-id=2

 

同理node4的数据流来源为node3:

[Harvest@node4 ~] repmgr -h node3 -U repmgr -d repmgr -f /etc/repmgr.conf standby clone --upstream-node-id=3
[Harvest@node4 ~] repmgr -f /etc/repmgr.conf standby register --upstream-node-id=3

 

以上,使用repmgr的级联复制配置完成。

 

参考

1.repmgr手册 :https://repmgr.org/docs/current/index.html

2.中文版手册:http://citusdb.cn/?p=1068

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