The 12 factor app states that applications should read config from environment variables. It implies separation of code and config. That’s about it, but there’s good bones here. I want something bigger from this factor. Specifically that applications may be deployed to new environments without any code changes. This requires a few additions:

1. Configure the process through command options and environment variables
2. Prefer explicit configuration over implicit configuration 
3. Use a dry run option to verify config sanity
4. Fail fast on any configuration error

Mentioned in Show

• Where, What, and How to Test on the Ruby Testing Podcast

Resources

• The 12 Factor App
• My Review & Analysis on The DevOps Handbook
• My Review & Analysis on Accelerate
• Software Development in 3 Principles & 4 Metrics

Books

• The DevOps Handbook by Gene Kim, Jez Humble, John Willis, Patrick Debois
• Accelerate by Nicole Forsgren, Jez Humble, Gene Kim