Skip to content

Domains

The domains package contains all the application domain logic separated by domains (this template provides a single domain: books).

Each domain should be self-contained and not invoke logic from other domains directly. Same as we do for gateways, or 3rd party providers, other domains should be accessed through the use of interfaces.

Using interfaces will:

  • Make sure domains do not depend on each other
  • Make easier to replace the concrete implementation with a HTTP adapter when the domain is extracted in a microservice

Book domain structure

The domains.book package provides an example implementation for a domain. It contains a list of public and protected modules.

Public package and modules are used by the application to invoke the domain functionalities:

  • The main domains.book package provides the entrypoint for our application: the BookService class. We export it here from the domains.book._service module to hide protected entities that should not be accessed directly.
  • The domains.book.interfaces provides the BookServiceInterface protocol to be used for Inversion of Control (we don't currently use it in this application because Clean Architecture doesn't enforce Inversion of Control from the http application, and we don't have yet implemented other domains)
  • The domains.book.dto provides the data transfer objects required to invoke the BookService class.
  • The domains.book.events provides the event data structures that the domain is able to emit. They can be used by other domains to implement event handlers.

Protected package and modules are used by the implementation of the books domain and can be used to bootstrap the application:

  • The domains.book._gateway_interfaces contains the gateway protocols against which the domain logic is implemented. We use them to configure the dependency injection container.
  • The domains.book._models contains the domain models. We use them also to bootstrap the SQLAlchemy imperative mapping in bootstrap.storage.SQLAlchemy package.
  • The domains.book._service contains the BookService implementation.
  • The domains.book._tasks contains the implementation of dramatiq tasks for operations that can be queued without waiting for a result (e.g. send an email, invalidate cache).