How to replicate PostgreSQL

So far we've learnt how to run PostgreSQL as per chapter 1.
We've also learnt how to configure PostgreSQL with our custom configuration file as per chapter 2.

In this chapter we will setup a second PostgreSQL instance.
Then we will learn how to configure our first PostgreSQL instance to replicate its data to the new second instance.
This will essentially give us a primary and a secondary server for better availability in case we lose our primary server.

Documentation on HA \ replication \ failover modes

Get our Primary PostgreSQL up and running

Let's start by running our PostgreSQL in docker

Few things to note here:

We start our instance with a different name to identify it as the first instance with the --name postgres-1 flag and 2 for the second instance
Set unique data volumes for data between instances
Set unique config files for each instance
Create and run our docker containers on the same network

Create a new network so our instances can talk with each other:

docker network create postgres

Start with instance 1:

cd storage/databases/postgres/3-replication

docker run -it --rm --name postgres-1 `
--net postgres `
-e POSTGRES_USER=postgresadmin `
-e POSTGRES_PASSWORD=admin123 `
-e POSTGRES_DB=postgresdb `
-e PGDATA="/data" `
-v ${PWD}/postgres-1/pgdata:/data `
-v ${PWD}/postgres-1/config:/config `
-p 5000:5432 `
postgres:15.0 -c 'config_file=/config/postgresql.conf'

Start instance 2:

cd storage/databases/postgres/3-replication

docker run -it --rm --name postgres-2 `
--net postgres `
-e POSTGRES_USER=postgresadmin `
-e POSTGRES_PASSWORD=admin123 `
-e POSTGRES_DB=postgresdb `
-e PGDATA="/data" `
-v ${PWD}/postgres-2/pgdata:/data `
-v ${PWD}/postgres-2/config:/config `
-p 5000:5432 `
postgres:15.0 -c 'config_file=/config/postgresql.conf'