aws-ecs

aws-ecs Best Practices

This guide outlines the definitive best practices for developing and deploying applications on Amazon Elastic Container Service (ECS). Adhere to these principles to ensure your applications are secure, performant, and maintainable.

1. Code Organization and Structure

1.1. Immutable Container Images

Always build immutable container images. Any change to code or dependencies must trigger a new image build and deployment. This ensures reproducibility and simplifies rollbacks.

❌ BAD: Modifying container contents at runtime (e.g., downloading dependencies on startup).

# Dockerfile
FROM node:18-alpine
WORKDIR /app
COPY package.json .
RUN npm install # Installs dependencies during build
COPY . .
CMD ["sh", "-c", "npm install && npm start"] # Re-installs on every run!

✅ GOOD: Bake all dependencies into the image during the build process.

# Dockerfile
FROM node:18-alpine AS builder
WORKDIR /app
COPY package.json package-lock.json ./
RUN npm ci --omit=dev # Install production dependencies
COPY . .
RUN npm run build # Build application assets

FROM node:18-alpine AS runner
WORKDIR /app
COPY --from=builder /app/node_modules ./node_modules
COPY --from=builder /app/dist ./dist # Copy built assets
EXPOSE 3000
CMD ["node", "dist/main.js"] # Run the built application

1.2. Single Process Per Container

Each container must run only one foreground application process. This allows ECS to effectively manage the container's lifecycle, health checks, and resource allocation.

❌ BAD: Using process managers like supervisord to run multiple applications.

# Dockerfile
CMD ["supervisord", "-c", "/etc/supervisord.conf"]
# supervisord.conf might start Nginx, a Python app, and a cron job.

✅ GOOD: Decouple services into separate containers and task definitions.

# Dockerfile for a single application
CMD ["python", "app.py"]

Context: If services are tightly coupled (e.g., a web server and a sidecar agent that must run on the same host), use a multi-container task definition. Otherwise, deploy them as separate services.