Docker Deep Dive

Docker Deep Dive

Go beyond basics with advanced Docker concepts for production: multi-stage builds, layer optimization, health checks, and resource management.

Multi-Stage Builds

  # Build stage
  FROM node:20-alpine AS builder
  WORKDIR /app
  COPY package*.json ./
  RUN npm ci --only=production
  COPY . .
  RUN npm run build

  # Production stage
  FROM node:20-alpine
  WORKDIR /app
  COPY --from=builder /app/dist ./dist
  COPY --from=builder /app/node_modules ./node_modules
  EXPOSE 3000
  CMD ["node", "dist/main.js"]

  # Result: Small production image (~150MB vs ~900MB)

Docker Health Checks

  # In Dockerfile
  HEALTHCHECK --interval=30s --timeout=3s --retries=3 \
    CMD curl -f http://localhost:3000/health || exit 1

  # Check container health
  docker inspect --format='{{.State.Health.Status}}' mycontainer
  # healthy | unhealthy | starting

Resource Limits

  # Limit CPU and memory
  docker run -d \
    --name web \
    --cpus="1.5" \
    --memory="512m" \
    --memory-swap="512m" \
    -p 80:80 \
    nginx:alpine

  # Docker Compose
  services:
    web:
      image: nginx:alpine
      deploy:
        resources:
          limits:
            cpus: '1.5'
            memory: 512M
          reservations:
            cpus: '0.5'
            memory: 256M

Advanced Networking

  # Create custom bridge network
  docker network create --driver bridge \
    --subnet 172.20.0.0/16 \
    --ip-range 172.20.240.0/20 \
    app-network

  # Connect containers
  docker run -d --name db --network app-network postgres:15
  docker run -d --name api --network app-network myapp:latest

  # Containers can now reach each other by name
  # api → db:5432 (DNS resolution)