private void copyTrackingHeaders(HttpResponse sourceResponse, HttpResponse targetResponse) {
    for (String header : RestUtils.TrackingHeaders.TRACKING_HEADERS) {
      if (sourceResponse.headers().contains(header)) {
        targetResponse.headers().set(header, sourceResponse.headers().get(header));
      }
    }
  }
Copy tracking headers (if any) from sourceResponse to targetResponse.
@param sourceResponse the source response with the tracking headers.
@param targetResponse the target response that the tracking headers will be copied over.
ambry-rest/src/main/java/com/github/ambry/rest/NettyResponseChannel.java