gRPC: per-client interceptors

[michalszynkiewicz]

Description

For gRPC services we now have @GlobalInterceptors and interceptors registered for specific servies.
We likely need something similar for clients, so that a user can attach an interceptor to a specific client

CC @cescoffier @mkouba

Implementation ideas

No response

[quarkus-bot]

/cc @cescoffier

[mkouba]

Hm, so currently any bean that implements ClientInterceptor is registered automatically? If so then we're quite inconsistent ;-)

Anyway, I think that we can reuse the @io.quarkus.grpc.GlobalInterceptor and possibly introduce the @RegisterClientInterceptor?

[cescoffier]

Exactly, I found out that when implementing the metrics support.

[sukolenvo]

Hi, I am trying to register client interceptor for a specific service. My bean graph is something like:

FooAuthClientInterceptor {
}

BeanA {
  @GrpcClient("foo")
  FooBlockingStub fooGrpcClient;
  
  @GrpcClient("bar")
  BarBlockingSub barGrpcClient;
}

BeanB {
  @GrpcClient("foo")
  FooBlockingStub grpcClient;
}

BeanC {
  @GrpcClient("foo")
  FooBlockingStub grpcClient;
}

Adding @RegisterClientInterceptor(FooAuthInterceptor.class) for every injection point seems a bit redundant (and could be easily forgotten for new services). Have you considered support for annotation for a type? Something like:

@RegisterFor("foo")
FooAuthClientInterceptor {
}

Alternatively if interceptor list could be set in GrpcClientConfiguration that would also be nit.

[cescoffier]

You can register a global interceptor. See https://quarkus.io/guides/grpc-service-consumption#client-interceptors

[sukolenvo]

Yes, but isn't global interceptor will attach to @GrpcClient("bar") as well? Its a bit risky to mark Auth interceptor as a default one - means credentials might go to the external service that wasn't intended to get them.

[michalszynkiewicz]

Yes it will.
You can work around it by delegating all interactions with a specific client to a single bean