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WHAT IS REPMGR?

repmgr is an open-source tool suite for managing replication and failover in a cluster of PostgreSQL servers. It enhances PostgreSQL's built-in hot-standby capabilities with tools to set up standby servers, monitor replication, and perform administrative tasks such as failover or manual switchover operations.

repmgr has provided advanced support for PostgreSQL's built-in replication mechanisms since they were introduced in 9.0. The current repmgr series, repmgr 5, supports the latest developments in replication functionality introduced from PostgreSQL 9.3 such as cascading replication, timeline switching and base backups via the replication protocol.

OPEN SOURCE FROM 2NDQUADRANT

repmgr is developed by 2ndQuadrant, the global experts in PostgreSQL support, training, development, migration and consultancy.

repmgr is free and open-source software licensed under the GNU Public License (GPL) v3. This means you are free to use and modify repmgr as you see fit, however any modifications you make may only be distributed under the same terms.

repmgr compatibility matrix

repmgr version Supported? Latest release Supported PostgreSQL versions

repmgr 5.x YES 5.0.0 (2019-10-15) 9.3, 9.4, 9.5, 9.6, 10, 11, 12

repmgr 4.x NO 4.4 (2019-06-27) 9.3, 9.4, 9.5, 9.6, 10, 11

repmgr 3.x NO 3.3.2 (2017-05-30) 9.3, 9.4, 9.5, 9.6

repmgr 2.x NO 2.0.3 (2015-04-16) 9.0, 9.1, 9.2, 9.3, 9.4

我们使用 postgresql 12.4 版本,所有使用repmgr 5.x 版本

使用文档为:

/docs/5.0/index.html

环境描述:

repmgr1: 192.168.112.66 centos 7.0 postgresql 12.4

repmgr2: 192.168.112.67 centos 7.0 postgresql 12.4

1.安装

2.1. Requirements for installing repmgr

A dedicated system user for repmgr is not required; as many repmgr and repmgrd actions require direct access to the PostgreSQL data directory, these commands should be executed by the postgres user.

我们使用 postgres 用户进行安装.

Important

yum install flex libselinux-devel libxml2-devel libxslt-devel openssl-devel pam-devel readline-devel

2.3. Installing repmgr from source

获取源码

2.3.3. Installation of repmgr from source

./configure

make

make install

3.1. Prerequisites for setting up a basic replication cluster with repmgr

If you want repmgr to copy configuration files which are located outside the PostgreSQL data directory, and/or to test switchover functionality, you will also need passwordless SSH connections between both servers, and rsync should be installed.

两台机器配置一下postgres 用户的 ssh 互信

3.2. PostgreSQL configuration

On the primary server, a PostgreSQL instance must be initialised and running. The following replication settings may need to be adjusted:

max_wal_senders = 10

max_replication_slots = 10

wal_level = 'hot_standby'

hot_standby = on

archive_mode = on

archive_command = '/bin/true'

Tip

Rather than editing these settings in the default postgresql.conf file, create a separate file such as postgresql.replication.conf and

include it from the end of the main configuration file with: include 'postgresql.replication.conf'.

我们在主库 repmgr1 创建 postgresql.replication.conf 文件,将如上6个参数写入文件中.

编辑 postgresql.conf 文件,在最后一行加入 include 'postgresql.replication.conf'

重启主库进行验证:

postgres=# show max_wal_senders;

max_wal_senders

-----------------

10

(1 row)

3.3. Create the repmgr user and database

createuser -s repmgr

createdb repmgr -O repmgr

3.4. Configuring authentication in pg_hba.conf

local replication all trust

host replication all 127.0.0.1/32 trust

host replication all 192.168.112.66/24 trust

host replication all 192.168.112.67/24 trust

local repmgr all trust

host repmgr all 127.0.0.1/32 trust

host repmgr all 192.168.112.66/24 trust

host repmgr all 192.168.112.67/24 trust

3.6. repmgr configuration file

Create a repmgr.conf file on the primary server. The file must contain at least the following parameters:

node_id=1

node_name='repmgr1'

conninfo='host=repmgr1 user=repmgr dbname=repmgr connect_timeout=2'

data_directory='/pgsoft/data'

3.7. Register the primary server

[postgres@repmgr1 data]$ repmgr -f /pgsoft/data/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

3.8. Clone the standby server

Create a repmgr.conf file on the standby server.

node_id=2

node_name='repmgr2'

conninfo='host=repmgr2 user=repmgr dbname=repmgr connect_timeout=2'

data_directory='/pgsoft/data'

Use the --dry-run option to check the standby can be cloned:

[postgres@repmgr2 pgsoft]$ repmgr -h repmgr1 -U repmgr -d repmgr -f /pgsoft/repmgr.conf standby clone --dry-run

NOTICE: destination directory "/pgsoft/data" provided

INFO: connecting to source node

DETAIL: connection string is: host=repmgr1 user=repmgr dbname=repmgr

DETAIL: current installation size is 31 MB

INFO: "repmgr" extension is installed in database "repmgr"

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

NOTICE: standby will attach to upstream node 1

HINT: consider using the -c/--fast-checkpoint option

INFO: all prerequisites for "standby clone" are met

If no problems are reported, the standby can then be cloned with:

[postgres@repmgr2 pgsoft]$ repmgr -h repmgr1 -U repmgr -d repmgr -f /pgsoft/repmgr.conf standby clone

NOTICE: destination directory "/pgsoft/data" provided

INFO: connecting to source node

DETAIL: connection string is: host=repmgr1 user=repmgr dbname=repmgr

DETAIL: current installation size is 31 MB

NOTICE: checking for available walsenders on the source node (2 required)

NOTICE: checking replication connections can be made to the source server (2 required)

INFO: creating directory "/pgsoft/data"...

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 /pgsoft/data -h repmgr1 -p 5432 -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 /pgsoft/data start

HINT: after starting the server, you need to register this standby with "repmgr standby register"

3.10. Register the standby

Register the standby server with:

[postgres@repmgr2 pgsoft]$ repmgr -f /pgsoft/repmgr.conf standby register

INFO: connecting to local node "repmgr2" (ID: 2)

INFO: connecting to primary database

WARNING: --upstream-node-id not supplied, assuming upstream node is primary (node ID 1)

INFO: standby registration complete

NOTICE: standby node "repmgr2" (ID: 2) successfully registered

验证:

[postgres@repmgr1 data]$ repmgr -f /pgsoft/data/repmgr.conf cluster show

----+---------+---------+-----------+----------+----------+----------+----------+----------------------------------------------------------

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repmgr基本配置

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