Interop: implement rpc-behavior server side

[zasweq]

Right now, rpc-behavior is only supported for C++ and Java. For tests which require rpc-behavior, interop tests overwrite server side to Java (see: https://github.com/grpc/grpc/blob/master/tools/run_tests/xds_k8s_test_driver/tests/outlier_detection_test.py#L58). It would be nice to have this support in Go as well so we can test our interop Go client with a Go server.

[zasweq]

See: grpc/grpc@be99673 for commit which added in C++.

[Aditya-Sood]

hi @dfawley @zasweq @sergiitk
is the fix for this already in-progress? if not I can pick the ticket

[dfawley]

No, this issue is unowned and not in progress. I'll assign it to you, thanks!

[Aditya-Sood]

hi @zasweq and @dfawley
based on the CPP commit shared above, I've been able to structure the helper methods like so

however there's a difference in the signature of the UnaryCall() method between the CPP implementation and ours in grpc-go - the former returns the Status Code in addition to setting the server ID and hostname, while the latter returns an error

hence could you please explain how the three possible return values of getStatusForRPCBehaviorMetadata() (nil, InvalidArgument and codes.Code(errCode)) should affect the response of UnaryCall()?

[Aditya-Sood]

hi @dfawley @zasweq
could you please clarify on the above?

[Aditya-Sood]

hi @easwars
would you be able to help with the above query? I am currently blocked for the fix because of it

also is there a slack channel/mailing list where I could reach out to other maintainers for queries like this?

[easwars]

also is there a slack channel/mailing list where I could reach out to other maintainers for queries like this?

We do have a mailing list at grpc-io@googlegroups.com, but posting your questions/concerns here on our repo on specific issues/PRs would get you better latency :)

however there's a difference in the signature of the UnaryCall() method between the CPP implementation and ours in grpc-go - the former returns the Status Code in addition to setting the server ID and hostname, while the latter returns an error

This is how I see the difference in the API between C++ and Go

• In C++, the rpc method handler has the following signature:
  • accepts a context, a request message, and a response message
    • the response message is an out parameter and is to be modified by the method handler
  • returns a grpc status
• In Go, the rpc method handler has the following signature:
  • it accepts a context and a request message
  • it returns a response message and an error
    • rpc handlers should generally wraps their errors using the status package (thereby, returning a status code and an error message)

Hope this helps.