What is the purpose of mirror routing in Envoy?

The purpose of mirror routing in Envoy is to send a copy of requests to another service for testing. This feature allows developers to safely test a new version of a service or an entirely different service without affecting the user experience. By mirroring the traffic—the original request continues to go to the primary service while a separate copy is sent to the mirror service—developers can gather insights about the performance or behavior of the mirror service in a live environment without any risk to production workloads. This approach fosters controlled testing and validation of new features, ensuring that they behave as expected before full deployment.

The other options do not accurately describe the functionality of mirror routing. For instance, mirror routing is not designed to exclusively send requests only to the main service or to redirect all requests to multiple services. Additionally, while it does not involve compressing request data for efficiency, it focuses specifically on traffic duplication for testing purposes.