code: public GrpcServer start() throws IOException {
      RetryUtils.retry("Starting gRPC server", () -> mServer.start(),
          new ExponentialBackoffRetry(100, 500, 5));
      mStarted = true;
      return this;
    }
docs: Start serving.
  
  @return this instance of {@link GrpcServer}
  @throws IOException when unable to start serving