The doStop method for StreamingSubscriberClient seems like it may be the opposite order of what would allow it to shut down most quickly and cleanly. It first calls runShutdown(), which calls messageDispatcher.stop();. That method waits until there are no outstanding messages. How do we ensure that no new messages come in? If they do, we could seemingly end up in a state where the client can never shut down because more messages come in constantly.

We should see if this can happen and if so, consider changing the order in which we do the shutdown so we do clientStream.closeSendWithError(Status.CANCELLED.asException()); first.