Advice exception handling not working with grpc-kotlin coroutines

The context

The plan is to implement the server stub with coroutine support from grpc-kotlin and exception handling via an exception handler advice.

The bug

While the registered advice picks up exceptions when implementing the normal blocking server stub (*ImplBase), when using coroutines support (*CoroutineImplBase) the exceptions are not handled and a Status.UNKNOWN is returned regardless.

Stacktrace and logs

Is there a stacktrace or a hint in the logs? (very important) Screenshots work as well, but don’t screenshot your logs.

Steps to Reproduce

Steps to reproduce the behavior:

1. Implement server stubs for the CoroutineImplBase
2. Implement and register GrpcAdvice
3. Force some exception to be thrown
4. Verify that advice methods are not reached

The application’s environment

Which versions do you use?

• Spring (boot): 2.4.0
• grpc-kotlin: 1.0.0
• grpc-spring-boot-starter: 2.11.0

Additional context

There seems to be a difference between the regular implementation where onHalfClose is called (and thus exception is handled) and the coroutine implementation.

To go around this, I quickly created a hacky interceptor like so:

import io.grpc.ForwardingServerCall
import io.grpc.Metadata
import io.grpc.ServerCall
import io.grpc.ServerCallHandler
import io.grpc.ServerInterceptor
import io.grpc.Status
import io.grpc.StatusException
import net.devh.boot.grpc.server.advice.GrpcAdviceExceptionHandler

@GrpcGlobalServerInterceptor
class ExceptionHandlingInterceptor(private val handler: GrpcAdviceExceptionHandler) : ServerInterceptor {

    private class ExceptionTranslatingServerCall<ReqT, RespT>(
        delegate: ServerCall<ReqT, RespT>,
        private val handler: GrpcAdviceExceptionHandler
    ) : ForwardingServerCall.SimpleForwardingServerCall<ReqT, RespT>(delegate) {

        override fun close(status: Status, trailers: Metadata) {
            if (status.isOk) {
                return super.close(status, trailers)
            }

            val problemStatus = handler.handleThrownException(status.cause) as StatusException
            super.close(problemStatus.status, trailers)
        }
    }

    override fun <ReqT : Any?, RespT : Any?> interceptCall(call: ServerCall<ReqT, RespT>?, headers: Metadata?, next: ServerCallHandler<ReqT, RespT>?): ServerCall.Listener<ReqT> {
        return next!!.startCall(ExceptionTranslatingServerCall(call!!, handler), headers)
    }
}

I haven’t delved deep into the underlying issue, so it can be a problem of the grpc-kotlin-stub:1.0.0 I’m using

[ST-DDT]

Definitely this year. Most likely in November. I can try to push the release at bit.

[skoret]

It really seems like a bug in grpc-kotlin, related issues: grpc/grpc-kotlin#141 and grpc/grpc-kotlin#184