docker-development-youtube-series/storage/databases/postgres/2-configuration

How to configure PostgreSQL

This is part 2 of our PostgreSQL series.
In this chapter, we learn about fundamentals of the Postgres configuration.

Many people make the mistakes of relying directly on Kubernetes PostgreSQL controllers and Helm charts without having any understanding of Databases.

Let's start where we left off, and review our simple PostgreSQL database:

Run a simple PostgreSQL database (docker)

cd storage/databases/postgres/2-configuration
docker run -it --rm --name postgres `
  -e POSTGRES_PASSWORD=admin123 `
  -v ${PWD}/pgdata:/var/lib/postgresql/data `
  -p 5000:5432 `
  postgres:15.0

Environment Variables

Many settings can be specified using environment variables.
I generally recommend not relying on default values and set most of the settings possible.

I personally prefer most or all settings in a configuration file, so it can be committed to source control.
This is where Environment variables are great because we can inject secrets there and keep passwords out of our configuration files and out of source control.

This will be important in Kubernetes later on.

We will not learn all or even most of the configurations in this chapter, as PostgreSQL has a lot of depth. So we will only learn what we need, one step at a time.

Let's take a look at some basic configurations here

Let's set a few things here:

Environment Variable	Meaning
POSTGRES_USER	Username for the Postgres Admin
POSTGRES_PASSWORD	Password for the Postgres Admin
POSTGRES_DB	Default database for your Postgres Server
PGDATA	Path where data is stored

Configuration files

If we take a look at our docker mount that we defined in our docker run command:

-v ${PWD}/pgdata:/var/lib/postgresql/data

The {PWD}/pgdata folder that we have mounted contains not only data, but some defaut configuration files that we can explore.

Three files are important here:

Configuration file	Meaning	Documentation
pg_hba.conf	Host Based Authentication file	Official Documentation
pg_ident.conf	User Mappings file	Official Documentation
postgresql.conf	PostgreSQL main configuraiton

The pg_hba.conf File

We'll start this guide with the host based authentication file.
This file is automatically created in the data directory as we see.
We should create a copy of this file and configure it ourselves.

It controls who can access our PostgreSQL server.
Let's refer to the official documentation as well as walk through the config.
The config file itself has a great description of the contents.

As mentioned in the previous chapter, it's always good not to rely on default configurations. So let's create our own pg_hba.conf file.

We can grab the content from the default configuration and we may edit it as we go.

# TYPE  DATABASE        USER            ADDRESS                 METHOD

# "local" is for Unix domain socket connections only
local   all             all                                     trust
# IPv4 local connections:
host    all             all             127.0.0.1/32            trust
# IPv6 local connections:
host    all             all             ::1/128                 trust
# Allow replication connections from localhost, by a user with the
# replication privilege.
local   replication     all                                     trust
host    replication     all             127.0.0.1/32            trust
host    replication     all             ::1/128                 trust

host all all all scram-sha-256

The pg_ident.conf File

This config file is a mapping file between system users and database users.
Let's refer to the official documentation and walk through the config.
This is not a feature that we will need in this series, so we will skip this config for the time being.

The postgresql.conf File

This configuration file is the main one for PostgreSQL.
As you can see this is a large file with in-depth tuning and customization capability.

docker run -d --rm --name postgres-1 `
  --net postgres `
  -e POSTGRES_USER=postgresadmin `
  -e POSTGRES_PASSWORD=admin123 `
  -e POSTGRES_DB=postgresdb `
  -e PGDATA=/var/lib/postgresql/data/pgdata `
  -p 5000:5432 `
  -v ${PWD}/archive:/mnt/server/archive `
  -v ${PWD}/postgres-1/pgdata:/var/lib/postgresql/data/pgdata `
  -v ${PWD}/postgres-1/postgresql.conf:/etc/postgresql/postgresql.conf `
  -v ${PWD}/postgres-1/pg_hba.conf:/var/lib/postgresql/data/pgdata/pg_hba.conf `
  postgres:14.4 -c 'config_file=/etc/postgresql/postgresql.conf'