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The 12 Factor App methodology is a set of best practices for building cloud-native applications that are scalable, maintainable, and portable. Below is a breakdown of each principle, along with practical commands and steps to implement them effectively.
1. Codebase: Single Codebase in Version Control
- Maintain one codebase per application, tracked in Git or another VCS.
- Avoid multiple repos for the same app.
Commands:
git init git add . git commit -m "Initial commit" git remote add origin <repository-url> git push -u origin main
2. Dependencies: Explicitly Declare and Isolate
- Use dependency managers like pip (Python), npm (Node.js), or Maven (Java).
- Avoid relying on system-wide packages.
Example (Python):
pip freeze > requirements.txt # Export dependencies pip install -r requirements.txt # Install dependencies
3. Config: Store Configuration in the Environment
- Use environment variables instead of hardcoding configs.
- Tools: `dotenv` (Node.js/Python), Kubernetes ConfigMaps.
Bash Example:
export DATABASE_URL="postgres://user:pass@localhost:5432/db" echo $DATABASE_URL
4. Backing Services: Treat as Attached Resources
- Databases, caches, and message queues should be loosely coupled.
- Use Docker or Kubernetes to manage services.
Docker Example:
docker run --name redis -d redis docker run --link redis:redis -e REDIS_URL=redis://redis my-app
5. Build, Release, Run: Strict Separation
- Build: Convert code into an executable (e.g., Docker image).
- Release: Combine build with config.
- Run: Execute the app in the target environment.
Docker & Kubernetes:
docker build -t my-app . kubectl apply -f deployment.yaml
6. Processes: Execute as Stateless Processes
- Avoid storing session data locally. Use Redis or Memcached.
Redis CLI:
redis-cli SET user:session "data" redis-cli GET user:session
7. Port Binding: Export Services via Port
- Apps should self-host (e.g., Flask, Express).
Python Flask Example:
from flask import Flask
app = Flask(<strong>name</strong>)
@app.route("/")
def home(): return "Hello, Cloud!"
if <strong>name</strong> == "<strong>main</strong>": app.run(host='0.0.0.0', port=5000)
8. Concurrency: Scale via Process Model
- Use horizontal scaling (containers, Kubernetes).
Kubernetes Scaling:
kubectl scale deployment my-app --replicas=5
9. Disposability: Fast Startup & Graceful Shutdown
- Handle SIGTERM for graceful shutdowns.
Python Signal Handling:
import signal
def handle_exit(signum, frame):
print("Shutting down...")
signal.signal(signal.SIGTERM, handle_exit)
10. Dev/Prod Parity: Keep Environments Similar
- Use Docker & Kubernetes for consistency.
Docker Compose Example:
services: web: image: my-app ports: ["5000:5000"] redis: image: redis
11. Logs: Treat as Event Streams
- Pipe logs to stdout/stderr and use tools like ELK Stack.
Linux Logs:
journalctl -u my-service -f # Follow logs
12. Admin Processes: Run as One-Off Tasks
- Use Docker exec or Kubernetes jobs.
Kubernetes Job Example:
apiVersion: batch/v1 kind: Job metadata: name: db-migration spec: template: spec: containers: - name: migrator image: my-app command: ["python", "manage.py", "migrate"]
What Undercode Say
The 12 Factor App methodology is essential for modern cloud-native development. By following these principles, you ensure scalability, maintainability, and resilience. Key takeaways:
– Use environment variables for configs.
– Stateless apps scale better.
– Docker & Kubernetes simplify deployments.
– Logs should be streamed, not stored in files.
Expected Output: A well-structured, cloud-optimized application that is easy to deploy, scale, and maintain.
Further Reading:
References:
Reported By: Ashsau Are – Hackers Feeds
Extra Hub: Undercode MoN
Basic Verification: Pass ✅
