HttpResponse getHttpResponse(NettyClient.ResponseParts responseParts) {
    HttpResponse httpResponse = (HttpResponse) responseParts.queue.poll();
    if (httpResponse == null) {
      throw new IllegalStateException(
          "Should have received response. completion context: " + responseParts.completionContext);
    }
    return httpResponse;
  }
@param responseParts a {@link NettyClient.ResponseParts}.
@return the first response part, which should be a {@link HttpResponse}.
@throws IllegalStateException if the response part queue is empty.
ambry-frontend/src/integration-test/java/com/github/ambry/frontend/FrontendIntegrationTestBase.java