Adding persistent state to the application

We created an application that consists of microservices, and that doesn't have a persistent state – the application is empty on every restart. Fixing this is simple: map the persistent volume to a folder of the container. Since no one microservice of our application keeps the data in files, but the PostgreSQL database does, we only need to attach a folder to a database container. Copy docker-compose.test.yml to docker-compose.prod.yml and add the following changes:

services:
  db:
    image: postgres:latest
    restart: always
    environment:
      - POSTGRES_USER=postgres
      - POSTGRES_PASSWORD=password
    volumes:
      - database_data:/var/lib/postgresql/data
  # other containers definition
volumes:
  database_data:
    driver: local

We attached a volume with the name database_data to the /var/lib/postgresql/data path...