@Override
  public long getBlobBytesReceived() {
    return blobBytesReceived.get();
  }
Processes a single decoded part in a multipart request. Exposes the data in the part either through the channel
itself (if it is the blob part) or via {@link #getArgs()}.
@param part the {@link InterfaceHttpData} that needs to be processed.
@throws RestServiceException if the request channel is closed, if there is more than one part of the same name, if
                             the size obtained from the headers does not match the actual size of the blob part or
                             if {@code part} is not of the expected type ({@link FileUpload}).
ambry-rest/src/main/java/com/github/ambry/rest/NettyMultipartRequest.java