Cancelled status code not reported in the gRPC server metrics

[ceremo]

Hi,

cancelled status codes are not reported in the gRPC server metrics, metrics in these cases are reported without the tag status code because GrpcServerObservationContext is not updated with the cancelled. For us it's important the gRPC server metric give us info of the status codes, and this could be improved for example modifying the onCancel method of the ObservationGrpcServerCallListener before running the stop operation, something like this:

  @Override
  public void onCancel() {
    try (final Scope scope = this.observation.openScope()) {
      super.onCancel();
    } finally {
      if (this.observation.getContext() instanceof final GrpcServerObservationContext obsCtx) {
        obsCtx.setStatusCode(Status.Code.CANCELLED);
      }
      this.observation.stop();
    }
  }

I have created a demo to reproduce easily cancelleds, the service has a delay of 5 seconds to give time to the client to cancel the request, you could make the call using postman or a simple grpc client with a deadline lower than 5 seconds.

Thanks for your time.

[ttddyy]

Observing the behavior of cancel, it seems the status code doesn't change even if the request is canceled.
Instead, the ServiceCall#isCancelled returns true for canceled requests.

So, I'm inclined to add GrpcServerObservationContext#isCancelled, which becomes a low cardinality tag, to indicate whether the request has been canceled or not, then keep the existing status code unchanged.

[ceremo]

It works for me, cancellations in webflux are defined using connectionAborted.