Potsgres Setup

We use Postgres as our relational database. In this exercise, you will learn how to set up Postgres on your Digital Ocean Droplet. Later we will connect it to the hotelAPI Javalin application.

Introduction - flashback to 2nd semester

On 2nd semester we installed Postgres on our Digital Ocean Droplet. We used a docker-compose.yml file to set up the Postgres database. The file looked roughly like this:

# db: Postgresql data base server som kører på port 5432

version: '3'

services:

  db:
    image: postgres:16.2
    container_name: db
    restart: unless-stopped
    networks:
      - backend
    environment:
      POSTGRES_USER: ${POSTGRES_USER}
      POSTGRES_PASSWORD: ${POSTGRES_PASSWORD}
    volumes:
      - ./data:/var/lib/postgresql/data/
      - ./db/init.sql:/docker-entrypoint-initdb.d/init.sql
    ports:
      - "5432:5432"

networks:
  backend:
      name: backend

If you went through that setup on 2nd semester, as most did, you will have this compose file already on your Droplet. The docker-compose file is located in the ~jetty/2semDockerSetupRemote folder. If you don’t have it, then follow the 2nd semester tutorial and get on track.

Step 1: Update the Docker Compose File

We don’t want to loose our data, so we will keep the db service running on the backend network. This is the network that the hotelAPI service will connect to later. For security reasons, we will add environment variables for the Postgres user and password and store them in a an external .env file:

1. Navigate to the ~jetty/2semDockerSetupRemote folder on your Droplet.
2. Open the docker-compose.yml file in an editor (nano).

3. Update the file with the following content:

   version: '3'
   
   services:
   
     db:
       image: postgres:16.2
       container_name: db
       restart: unless-stopped
       networks:
         - backend
       environment:
         POSTGRES_USER: ${POSTGRES_USER}
         POSTGRES_PASSWORD: ${POSTGRES_PASSWORD}
       volumes:
         - ./data:/var/lib/postgresql/data/
         - ./db/init.sql:/docker-entrypoint-initdb.d/init.sql
       ports:
         - "5432:5432"
       healthcheck:
         test: ["CMD-SHELL", "pg_isready -U postgres"]
         interval: 30s
         timeout: 10s
         retries: 5
         start_period: 10s
   
   networks:
     backend:
       name: backend
   

4. It’s close to the 2nd semester version, but we have removed the mem_limit and mem_reservation settings. We have also added ${POSTGRES_USER} and ${POSTGRES_PASSWORD} as environment variables. These will be set in the .env file later. We have also added a healthcheck to the service, that we will use later.

5. Save the file and exit the editor.

Step 2: Create the .env file

1. Create a .env file in the ~jetty/2semDockerSetupRemote folder:

    nano .env
   

2. Add the following content to the file:

    POSTGRES_USER=postgres
    POSTGRES_PASSWORD=<dit_sikre_password>
   

   Replace <dit_sikre_password> with a secure password.

3. Save the file and exit the editor.

Step 3: Start the Postgres Service

1. Start the Postgres service with Docker Compose:

    docker-compose up -d
   

2. Check that the service is running:

    docker ps
   

   You should see the db service running.

3. Check the logs from the service:

    docker logs db
   

Next step

Now that the Postgres service is running, we can connect the hotelAPI service to it. Follow the Hotel API exercise to set up the hotelAPI Javalin web application on your Digital Ocean Droplet.