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LocalDatabaseSetup.md

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Docker and PostgreSQL Setup with Docker Compose

1. What is Docker?

Docker is a platform that allows you to package applications and their dependencies into containers. Containers are lightweight, portable units that run the same regardless of the environment, ensuring consistency from development to production.

2. What is Docker Compose?

Docker Compose is a tool for defining and running multi-container Docker applications. Using a YAML file (docker-compose.yml), you can configure all your application's services, making it easy to start and stop them with a single command.

3. Using Docker Compose for PostgreSQL Setup

Docker Compose simplifies the setup of a PostgreSQL database by allowing you to define the database service in a configuration file. This ensures that every developer sets up the database in the same way, reducing inconsistencies and setup time.

4. Explanation of the Provided docker-compose.yml File

Here's a breakdown of your docker-compose.yml file:

version: '3.1'

services:
  db:
    image: postgres # Uses the official PostgreSQL image
    container_name: dodao-ui-db # Names the container for easy reference
    restart: always # Automatically restarts the container if it stops
    environment:
      POSTGRES_USER: admin # Sets the database user to 'admin'
      POSTGRES_PASSWORD: admin # Sets the database password to 'admin'
      POSTGRES_DB: next_app_localhost_db # Creates a database named 'next_app_localhost_db'
    ports:
      - '5432:5432' # Exposes port 5432 to the host
    volumes:
      - ./data:/var/lib/postgresql/data # Persists data to the './data' folder
      - ./init.sql:/docker-entrypoint-initdb.d/init.sql # Runs 'init.sql' on first run
  • Services: Defines a single service called db, which is our PostgreSQL database.
  • Image: Specifies the Docker image to use (PostgreSQL).
  • Container Name: Assigns a custom name to the container.
  • Environment Variables: Sets up database credentials and the initial database.
  • Ports: Maps the container's PostgreSQL port to the host machine.
  • Volumes:
    • ./data:/var/lib/postgresql/data: Binds the local data folder to the container's data directory for persistence.
    • ./init.sql:/docker-entrypoint-initdb.d/init.sql: Executes the init.sql script when the database initializes.

5. How Data is Stored in the "data" Folder

The line ./data:/var/lib/postgresql/data maps the container's data directory to a local folder named data. This means:

  • Data Persistence: Your database data is saved on your local machine.
  • Portability: You can back up or inspect the data directly from the data folder.
  • Container Independence: Even if the Docker container is removed, your data remains intact in the data folder.

6. How init.sql Works

The line ./init.sql:/docker-entrypoint-initdb.d/init.sql mounts your local init.sql script into the container's initialization directory. Here's what happens:

  • Automatic Execution: When the PostgreSQL container is run for the first time, it looks for scripts in /docker-entrypoint-initdb.d/ and executes them.
  • Database Initialization: init.sql can contain SQL commands to set up your database schema, tables, or seed data.
  • One-Time Setup: This script runs only if the database is not already initialized (i.e., when the data folder is empty).

7. Logs

Note: Ensure that docker container is running fine by checking the terminal logs when you run the command. If you see the below statements in the logs then that means docker container is running fine:

  dodao-ui-db  | running bootstrap script ... ok
  .
  .
  .
  dodao-ui-db  | CREATE ROLE
  dodao-ui-db  | CREATE TABLE
  dodao-ui-db  | ALTER TABLE
  .
  .
  .
  dodao-ui-db  | INSERT 0 1
  dodao-ui-db  | INSERT 0 1
  .
  .
  .
  dodao-ui-db  | 2024-09-26 13:38:40.557 UTC [1] LOG:  database system is ready to accept connections

8. How to Recreate the Database to Start from Scratch

To reset your database:

  1. Stop and Remove Containers: Run docker-compose down to stop and remove the containers.
  2. Delete the Data Folder: Remove the data folder by executing rm -rf ./data. This deletes all your database data.
  3. Restart the Containers: Run docker-compose up to start fresh. The init.sql script will run again, reinitializing your database.

Warning: Deleting the data folder will permanently remove all data stored in the database. Ensure you have backups if needed.

By using Docker and Docker Compose, you streamline the setup process, ensuring consistency and reducing the chances of environment-related bugs. The docker-compose.yml file provided sets up a PostgreSQL database that's easy to manage and share among your development team.

Checklist

  • I understand the purpose of Docker and Docker Compose.
  • I understand how the docker-compose.yml file sets up the PostgreSQL database.
  • I understand how data is stored in the data folder for persistence.
  • I understand how the init.sql script initializes the database.
  • I know how to check the logs to ensure the database is setup properly.
  • I know how to stop the postgesql on my local machine and have it running in a docker container.
  • I know how to recreate the database to start from scratch.