🚀 Week 2 Assignment: Docker Basics Lab — Containers, Volumes & Networking

📌 Overview

This lab demonstrates building and running a simple FastAPI service with PostgreSQL using Docker and Docker Compose.
The project shows:

• A minimal API containerized with a slim, non-root Dockerfile
• A two-service stack (API + Postgres) connected via a private network
• Data persistence with a named volume
• Structured logging and a /health endpoint
• Horizontal scaling of the API service
• Reflection on GitHub Copilot usage

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🗂️ Project Structure

docker-basics-lab/ │── app.py │── requirements.txt │── Dockerfile │── docker-compose.yml │── .dockerignore │── README.md

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🛠️ Tools & Versions

• Docker Engine: 28.4.0
• Docker Compose: v2.39.2
• Python: 3.11-slim (base image)
• FastAPI: 0.115.0
• Uvicorn: 0.30.6
• Postgres: 16

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▶️ Build & Run

1. Build and start containers

docker compose up -d --build

2. Check running containers
docker compose ps


Expected:

NAME                       STATUS          PORTS
docker-basics-lab-api-1    Up              0.0.0.0:8000->8000/tcp
docker-basics-lab-db-1     Up              5432/tcp

3. Call health endpoint
curl http://localhost:8000/health


Expected:

{"status":"ok"}

4. View logs
docker compose logs -f api


Expected log line:

{"event":"health","ok":true}

💾 Persistence Demo

Create table & insert row:

docker exec -it $(docker ps -qf "name=_db_") \
psql -U app -d appdb -c "CREATE TABLE notes(id SERIAL PRIMARY KEY, msg TEXT);"

docker exec -it $(docker ps -qf "name=_db_") \
psql -U app -d appdb -c "INSERT INTO notes(msg) VALUES ('hello volume');"


Restart DB:

docker compose restart db


Query data:

docker exec -it $(docker ps -qf "name=_db_") \
psql -U app -d appdb -c "SELECT * FROM notes;"


✅ Expected: Row with "hello volume" remains after restart.
This confirms the named volume is persisting data.

📈 Scaling Demo

Scale API to 3 replicas:

docker compose up -d --scale api=3
docker compose ps


Expected: 3 containers of API running, all connected to the same DB.