Let’s start shall we!

Building the Setup

All the steps below will use the following terms:

dbhost1: first database host running on 192.168.0.100

dbhost2: second database host running on 192.168.0.101

pgbouncer-host: host running pgbouncer on 192.168.0.102

Setup Instructions:

  1. Install dependencies.
  2. Configure ssh access between db nodes.
  3. Configure databases.
  4. Configure PostgreSQL replication.
  5. Configure replication manager.
  6. Clone slave.
  7. Configure pgBouncer.
  8. Failover.

Each step title will have between parentheses the hosts that the step applies to.

1) Install Dependences (dbhost1, dbhost2, pgbouncer-host)

The default ubuntu 14.04 installation does not include PostgreSQL 9.4 so we will need to add the repository:
Create the file /etc/apt/sources.list.d/pgdg.list, and add a line for the repository

Import the repository signing key, and update the package lists

Install the dependencies for database hosts (dbhost1,dbhost2)

Install the dependencies for pgBouncer host (pgbouncer-host)

2) Configure password-less ssh between dbhosts (dbhost1,dbhost2)

by default postgreSQL creates a postgres local linux user which is used to do all database management operations. To create slaves or recreate a master after failure repmgr requires that the user running the commands have password-less ssh access to the source host. Since the postgres user is the user which has permissions on the postrgres directories, we will configure that user for ssh.
switch to the user

create ssh key pair

copy the publich key id_rsa.pub contents and add it to the authorized_keys file in the other host’s postgres user ssh directory. For more details see

test that you can ssh between servers before going to the next step.

3) Configure Databases and users (dbhost1)

We will need two databases one will be used by repmgr and the other will be our application database. All commands are to be executed using the postgres user.

for repmgr database

For our application database
createuser test_user
$ createdb test_db -O test_user

since this user will be used by the applications (clients) we will set a password for it. Run the following command from inside a psql shell with the default postgres user.

4) Configure PostgreSQL replication (dbhost1)

We will now configure the master db host (dbhost1) for replication. This is acheived by editing the postgresql.conf file and updating the follwing items

We also need to configure the authentication configuration (pg_hba.conf) to allow repmgr to access replication database and also allow password based access for our application database (test_db). We will add the following lines:

restart the postgres service after the changes are done

5) Configure Replication Manager (dbhost1,dbhost2)

We will need to create a repmgr.conf on each database host. The file could be stored anywhere but we will use /etc/repmgr/repmgr.conf.

The file contents for the dbhost1 should be

We are now ready to join our master to the replication topology. Using the postgres user run the command

Видим
2016-10-19 15:45:31] [NOTICE] master node correctly registered for cluster test with id 1 (conninfo: host=dockerbase112 user=repmgr dbname=repmgr)

and similarly for dbhost2 we need to create the file /etc/repmgr/repmgr.confwith the contents

6) Clone Slave (dbhost2)

ssh into our slave server dbhost

stop the postgresql service

run the following command using the postgres user to clone the master

start the postgresql server

register the slave as a standby

if all the previous steps ran successfully we should be able to see the state of our replication cluster using the command

and it should return an output like this

7) Configure pgBouncer (pgbouncer-host)

All pgBouncer needs is a configuration file pgbouncer.ini which can be stored anywhere in the system. The contents of the file should be