Events

An event is both a fact and a notification, something that already happened in the real world.

• No expectation on any future action

• Includes information about a status change that just happened

• Travels in one direction and it never expects a response (fire and forget)

• Very useful when...

  • Loose coupling is important

  • When the same piece of information is used by several services

  • When data needs to be replicated across application

A message in general is any interaction between an emitter and a receiver to exchange information. This implies that any event can be considered a messages but not the other way around.

There are several ways to use events in a EDA:

• Events as notifications

• Events to replicate data