Docker Composer

Name: docker-composer
Rating: 78
Author: codeswiftr

When to Use

•Setting up new projects with containers.
•Optimizing existing Docker configurations.
•Creating multi-service development environments.
•Preparing production-ready container images.

Best Practices

Dockerfile Optimization

•Use multi-stage builds to reduce image size.
•Order layers by change frequency (deps first, code last).
•Use specific base image tags, not latest.
•Run as non-root user for security.
•Use .dockerignore to exclude unnecessary files.

Base Image Selection

Use Case	Recommended Base
Python	python:3.12-slim
Node.js	node:20-alpine
Go	golang:1.22-alpine (build) + scratch/distroless (runtime)
Rust	rust:1.75-slim (build) + debian:slim (runtime)
Static files	nginx:alpine

Templates

Python FastAPI

dockerfile

# Build stage
FROM python:3.12-slim as builder

WORKDIR /app
RUN pip install uv

COPY pyproject.toml uv.lock ./
RUN uv sync --frozen --no-dev

# Runtime stage
FROM python:3.12-slim

WORKDIR /app
RUN useradd -r -s /bin/false appuser

COPY --from=builder /app/.venv /app/.venv
COPY src/ ./src/

ENV PATH="/app/.venv/bin:$PATH"
USER appuser

EXPOSE 8000
CMD ["uvicorn", "src.main:app", "--host", "0.0.0.0", "--port", "8000"]

Node.js

dockerfile

FROM node:20-alpine as builder

WORKDIR /app
COPY package*.json ./
RUN npm ci --only=production

FROM node:20-alpine

WORKDIR /app
RUN addgroup -g 1001 -S appgroup && adduser -S appuser -u 1001 -G appgroup

COPY --from=builder /app/node_modules ./node_modules
COPY dist/ ./dist/

USER appuser
EXPOSE 3000
CMD ["node", "dist/index.js"]

docker-compose.yml Template

yaml

version: '3.8'

services:
  app:
    build:
      context: .
      dockerfile: Dockerfile
      target: development
    ports:
      - "8000:8000"
    volumes:
      - ./src:/app/src:ro
    environment:
      - DATABASE_URL=postgresql://user:pass@db:5432/app
    depends_on:
      db:
        condition: service_healthy
    healthcheck:
      test: ["CMD", "curl", "-f", "http://localhost:8000/health"]
      interval: 30s
      timeout: 10s
      retries: 3

  db:
    image: postgres:16-alpine
    volumes:
      - postgres_data:/var/lib/postgresql/data
    environment:
      POSTGRES_USER: user
      POSTGRES_PASSWORD: pass
      POSTGRES_DB: app
    healthcheck:
      test: ["CMD-SHELL", "pg_isready -U user -d app"]
      interval: 10s
      timeout: 5s
      retries: 5

  redis:
    image: redis:7-alpine
    volumes:
      - redis_data:/data
    healthcheck:
      test: ["CMD", "redis-cli", "ping"]

volumes:
  postgres_data:
  redis_data:

.dockerignore Template

code

.git
.github
.env*
*.md
*.log
__pycache__
*.pyc
node_modules
.pytest_cache
.coverage
htmlcov
dist
build
*.egg-info
.venv
venv

Workflow

•Identify services needed (app, db, cache, etc.).
•Choose base images appropriate for each service.
•Write Dockerfile with multi-stage build.
•Create docker-compose.yml with health checks.
•Add .dockerignore to minimize context.
•Test locally before pushing to registry.

Output Checklist

• Multi-stage Dockerfile created.
• Non-root user configured.
• Health checks defined.
• Volumes for persistence.
• Environment variables documented.
• .dockerignore in place.