Service discovery is an architecture pattern used for components (micro-services) to locate each other. The DCAE platform uses server-side discovery and is using Consul as the service registry solution.
All components are required to register with Consul in order to be discovered. There are two methods of registration: self and 3rd party. The DCAE platform uses 3rd party registration which means components don't actually make the registration calls but defers that responsibility to a platform service.
Registrator is an open source application that is responsible for registering all components that run as Docker containers. Registrator watches the local Docker engine's activity log and will register and unregister a Docker container when the container is started and stopped.
The CDAP broker is a REST web service that is responsible for registering all components that run as CDAP applications.