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ral / 24092009

Primary ports kata

  • This kata is not about implementing an hexagonal architecture
  • There is an architecture already in place
  • This kata is about having a first-hand experience of the benefits and trade-offs of the architecture

Concepts

Reading list

Pamplona craftsmen timing

INTRODUCCIÓN Y PRIMERA PARTE

  • El ostíon: 15 mins: clonar repo, npm install, levantar web/consola, pedir implementar la división sin explicar absolutamente nada.
  • hands off: 15 mins: ¿menuda ostia eh? Explicación del código, cómo está organizado, qué habría que hacer para implementar la división. - hands on: 10 mins: implementar la división. - hands off: 20 mins: arquitectura en tres capas versus un adaptador por request. En ambos casos: controlador --> servicio --> repositorio. En éste ejercicio rompemos con esa idea. Contar cosas de las notas que pongo más abajo.

SEGUNDA PARTE: - hands on: 15 mins: Ejercicio2: implementar validación - hands on: 15 mins: Ejercicio 3: implementar cambio en las urls web - nota: si hay gente que va rápido, ofrecerles implementar los "extra exercises" del README

CIERRE: - repasar bondades y comparar ventajas desventajas de cada implementación - pedir feedback

Deliberate practice exercises

Add a new feature: division

  • Hint: don't forget about writing tests!
  • Check: there's no need to change the delivery. New features are automatically delivered though the web and console adapters

Add validation: division by zero is not allowed

  • Hint: the adapters should adapt the error accordingly e.g web responds with a 4xx status code
  • Check: By using the outside-in mindset, tests don't need to know the specifics about the validation implementation and they can focus exclusively on its visible effects.

Change the web route pattern from vertical/feature to vertical-feature

  • Check: changing all the web urls only requires changing one line of code

Free exploration ideas

Here are some ideas to try by yourself:

  • Implement authentication inside your hexagon
  • Log the request history with a secondary port e.g. RequestLogRepository
  • Change the primary port so that you can avoid exposing particular features in your adapters
  • Segregate requests into queries and commands
    • Do you see any relation between Ports and Adapters and CQRS?
    • Once you've done that, can you think of new delivery strategies you can follow?

Discussion

Ports and Adapters: features and architecture are decoupled so:

  • I can develop features without having to be aware of the architecture, and viceversa
  • I can test features without worrying about how they're delivered

Compare these options:

  • Classic layered architecture
  • Ports and Adapters with one adapter for each feature
  • Ports and Adapters with one primary port for all features

About dependencies: