Introduction to Code's 12 Rules

Code's 12 Rules, also known as "The Twelve Factor App," is a methodology for building software-as-a-service (SaaS) applications. It was created by Adam Wiggins and derived from his experience working on a SaaS project. The methodology is designed to help developers build scalable, maintainable, and portable applications in the cloud.

Markdown Overview of the 12 Rules

1. Codebase: One codebase tracked in revision control, many deploys.

• Maintain all software versions in a single codebase.
• Deploy only the necessary parts of the codebase each time.

2. Dependencies: Explicitly declare and isolate dependencies.

• Declare and control external software libraries and other dependencies.
• Use containers to isolate dependencies and ensure compatibility.

3. Config: Store configuration in the environment.

• Store configuration values such as API keys, credentials, and URLs in the environment.
• Avoid hardcoding configuration values in the codebase.

4. Backing services: Treat backing services as attached resources.

• Treat supporting services such as databases, message brokers, and email services as external resources.
• Connect to backing services through a well-defined interface.

5. Build, release, run: Strictly separate build and run stages.

• Separate the process of building the codebase from deploying and running it.
• Ensure that each stage has a well-defined interface.

6. Processes: Execute the app as one or more stateless processes.

• Avoid storing session state on individual servers.
• Use shared storage to store session data or use an external state management system.

7. Port binding: Export services via port binding.

• Use well-defined ports to expose the application's services.
• Avoid hardcoding network addresses in the codebase.

8. Concurrency: Scale out via the process model.

• Use a process model to scale the application horizontally.
• Design processes to be stateless and scalable.

9. Disposability: Maximize robustness with fast startup and graceful shutdown.

• Ensure that all processes can be started and stopped gracefully.
• Use tools such as container orchestration platforms to automate management.

10. Dev/prod parity: Keep development, staging, and production as similar as possible.

• Ensure that the various stages of the application's lifecycle are consistent.
• Use standardized tooling and environments to ensure consistency.

11. Logs: Treat logs as event streams.

• Use a centralized logging system to collect and analyze logs from all parts of the application.
• Store logs as event streams to enable searching and filtering.

12. Admin processes: Run admin/management tasks as one-off processes.

• Treat administrative tasks as one-off processes rather than features of the application.
• Use the same tooling and environments as the application to avoid inconsistencies.

Conclusion

Code's 12 Rules provide a useful methodology for building cloud-based applications. By following these rules, developers can create software that is scalable, maintainable, and portable - all essential qualities for software-as-a-service applications.