Domain Contexts

Sample app to demonstrate isolating domains

Domains involved

• Run context of the App
  • This is the context in which the application is being run. In our case it's IO
  • The application is either running or it's failed and unrecoverable'
• Handled The context of our services
  • This is the context used for expected errors
• Traced This context wraps the Handled context and provides a ReaderT with a TracedContext to access

Alternatives to ReaderT

• Java’s TheadLocal possible for context propagation only in case of synchronous invocations;
• Monix has Local implementation, which can deal with context propagation for Task and Future.
• ZIO has FiberRef for context propagation in terms of fiber
• Cats Effect IO’s recently got Fiber Locals similar to previous solutions

How to cause errors

Service Errors

• Edit the application.conf#external-api.uri value to a different url (e.g. external-api.uri = "https://google.com/" )

Program Errors

• http POST localhost:3000/domain/short author=shane name=tony

Database Errors

• http POST localhost:3000/domain/long author=Shane name=Tony

Happy Path

1.http localhost:3000/domain

2.http POST localhost:3000/domain/short author=Shane name=Tony

3.http localhost:3000/domain