Diferencia

Diferencia is designed to act as a proxy which intercepts calls to a service and multicast it to several instances of the same service. These instances are an old and new version of the service. Then when the response is returned from each instance, Diferencia will check if both responses are similar (we will see later what it means similar), and if it is the case, then the two implementations might be considered compatible and the new version implementation is regression-free.

In the previous schema, you can see that a request is multicasted to two instances of Service A, one being V1 and to other V2. Both return a response and then it is compared by Diferencia. Finally, notice that no response is returned but the result (in form of HTTP Status Code).

Since Diferencia does not return a real response, but a comparison, effectively means that you need to use Diferencia proxy for testing purposes (to check backward compatibility) and not as a production proxy like Envoy. This means that Diferencia might be used to run concrete tests for backward compatibility or using Traffic Shadowing/Mirroring technique.