container-orchestration

Container Orchestration

Facts verified as of 2026-07.

Docker and Kubernetes patterns for containerized applications.

Dockerfile Best Practices

# Use specific version, not :latest
FROM python:3.11-slim AS builder

# Set working directory
WORKDIR /app

# Copy dependency files first (better caching)
COPY requirements.txt .
RUN pip install --no-cache-dir -r requirements.txt

# Copy application code
COPY src/ ./src/

# Production stage (multi-stage build)
FROM python:3.11-slim

WORKDIR /app

# Create non-root user
RUN useradd --create-home appuser
USER appuser

# Copy from builder
COPY --from=builder /app /app

# Set environment
ENV PYTHONUNBUFFERED=1

# Health check
HEALTHCHECK --interval=30s --timeout=3s \
  CMD curl -f http://localhost:8000/health || exit 1

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

Dockerfile Rules

DO:
- Use specific base image versions
- Use multi-stage builds
- Run as non-root user
- Order commands by change frequency
- Use .dockerignore
- Add health checks

DON'T:
- Use :latest tag
- Run as root
- Copy unnecessary files
- Store secrets in image
- Install dev dependencies in production

Docker Compose

# docker-compose.yml
version: "3.9"

services:
  app:
    build:
      context: .
      dockerfile: Dockerfile
    ports:
      - "8000:8000"
    environment:
      - DATABASE_URL=postgres://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:15-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

volumes:
  postgres_data:

Kubernetes Basics