When a server unary interceptor executes, has the gRCP library verified at that point that the method being called actually exists? We record metrics by method name and this should be a low cardinality dimension. What I'd like to know is if there's any possibility in which case the interceptor would execute on a call to a method which doesn't exist? This could cause an attacker to spam the metrics backend.
Server call does method lookup first, if not found, it returns IMPLEMENTED: method not found. Then it does server interceptor here