12 Factors

1. Codebase

One codebase tracked in revision control, many deploys

  • git
  • Isolate code from dependencies and configuration
  • Ignore unnecessary files / folders when pushing
    • use .gitignore .cfignore 
       .DS_Store
 bin
 obj
 project.lock.json
 node_modules
 .vs
 .vscode
  • One codebase per microservice

2. Dependencies

Explicitly declare and isolate dependencies

  • npm, bower, nuget, gradle, maven

3. Config

Store config in the environment

  • Use configuration servers

.NET Core references a particular environment variable, ASPNETCORE_ENVIRONMENT to describe the environment the application is currently running in. This variable can be set to any value you like, but three values are used by convention: Development, Staging and Production

appsettings.Development.json, appsettings.Staging.json, appsettings.Production.json

NODE_ENV is an environment variable made popular by the express webserver framework.

4. Backing services

Treat backing services as attached resources

  • A backing service is any service the app consumes over the network as part of its normal operation
  • Databases, Queues, External services
  • cf bind-service myapp mybackingservice
  • For bindable services, Cloud Foundry adds connection details to the VCAP_SERVICES environment variable

5. Build, release, run

Strictly separate build and run stages

  • build: code + dependencies -> binary
  • release: build + configuration
  • run: execution
  • Have rollback plan
  • Don’t do live edit

6. Processes

Execute the app as one or more stateless processes

7. Port binding

Export services via port binding

  • In case of node use process.env.PORT
  • In case of .Net core use --server.urls=http://localhost:{port}

8. Concurrency

Scale out via the process model

9. Disposability

Maximize robustness with fast startup and graceful shutdown

10. Dev/prod parity

Keep development, staging, and production as similar as possible

  • File/Folder names are case-insensitive in Windows where as case-sensitive in linux/mac
  • Path and special folders are different
  • Use adapters

11. Logs

Treat logs as event streams

  • Dont use file logs

Viewing logs of CF apps

  cf logs appname
  cf logs appname --recent

Viewing logs in Azure sites

  curl -u $username:password https://sitename.scm.azurewebsites.net/api/logstream

12. Admin processes

Run admin/management tasks as one-off processes

Reference

12factor.net

Images

Image: dzone.com

The Cloud-Native Architecture

Image: pivotal.io