Docker Day 9: Mastering the Right Workflow for Local Development

Traditional Development vs Docker Development

Problems with the traditional approach

Dependencies are installed on the host machine, causing version conflicts between projects.

"It works on my machine" – environments are inconsistent.

New teammates spend half a day configuring the environment.

Advantages of Docker for development

Each project runs in an isolated container, preventing interference.

The environment is defined as code (Dockerfile, compose file).

Cloning the repository and running a single command starts the application.

Development environment compose file

services:
  api:
    build:
      context: .
      target: develop
    volumes:
      # Code sync – changes take effect instantly
      - .:/app
    environment:
      - DEBUG=true
      - DB_HOST=db
    depends_on:
      - db
      - redis
    command: ["uvicorn", "main:app", "--reload", "--host", "0.0.0.0", "--port", "8000"]

  db:
    image: postgres:16-alpine
    environment:
      POSTGRES_PASSWORD: secret
      POSTGRES_USER: app
      POSTGRES_DB: mydb
    volumes:
      - postgres_dev_data:/var/lib/postgresql/data

  redis:
    image: redis:7-alpine

volumes:
  postgres_dev_data:

Hot reload (real‑time code changes)

Method 1: Bind mount

services:
  api:
    volumes:
      - ./app:/app  # Host ./app mapped to container /app

Modifying files on the host instantly reflects inside the container.

Method 2: develop:watch (official recommendation, Docker Compose v2)

Compose v2 introduces develop:watch, which synchronizes files and restarts the container when changes are detected.

services:
  api:
    build: .
    develop:
      watch:
        - action: sync+restart
          path: ./app
          target: /app

Comparison

Bind mount – Direct host directory mapping; suitable for simple scenarios.

develop:watch – Intelligent sync + restart on file changes; recommended for formal development.

Frameworks such as Django or Rails already provide hot reload, automatically restarting on code changes.

Database connection

services:
  api:
    environment:
      DATABASE_URL: postgresql+asyncpg://app:secret@db:5432/mydb

  db:
    ports:
      - "5432:5432"  # Local IDE can connect via localhost:5432

Common development commands

# Start all services
docker compose up -d

# Start a specific service
docker compose up -d api

# View logs
docker compose logs -f api
docker compose logs -f   # all services

# Enter container for debugging
docker compose exec api bash

# Rebuild images
docker compose up -d --build

# Remove all data and start fresh
docker compose down -v   # -v also deletes volumes

Day 9 summary

Bind mount enables instant code changes.

Multi‑stage Dockerfile separates development and production configurations.

One command docker compose up -d launches the full development environment. develop:watch is the officially recommended hot‑reload solution.

New teammates only need Docker installed; a single command gets them running.