The elephant in the room with Istio is that the more functionality you move into sidecars, the harder issues become to to test and reproduce. This is because Istio is transparent to applications and runs out of band so it is much harder to write tests to verify your application works with the latest Istio manifest that is deployed. In theory great for operators as they get more control over network comms & security but bad for developer workflow.
It’s hard to imagine something easier and more reproducible for developers than connecting to localhost and having your request routed to the correct endpoint automatically, whether you’re on a disconnected laptop or in production. That’s the power of the ambassador pattern, which Envoy enables.
When the request is routed correctly, yes, but the question is when it's routed incorrectly (perhaps because information you're providing to Istio is incorrect but you haven't realized it yet, perhaps because of bugs in Istio).
