@Override
    public void onCompletion(Long result, Exception exception) {
      if (httpContent != null) {
        httpContent.touch("Release at channel " + channel.toString());
        httpContent.release();
      }
      callbackWrapper.updateBytesRead(result);
      continueReadIfPossible(-result);
      if (exception != null || isLast) {
        callbackWrapper.invokeCallback(exception);
      }
    }
Decreases reference counts of content if required, updates the number of bytes read and invokes
{@link ReadIntoCallbackWrapper#invokeCallback(Exception)} if {@code exception} is not {@code null} or if this is
the last piece of content in the request.
@param result The result of the request. This would be non null when the request executed successfully
@param exception The exception that was reported on execution of the request
ambry-rest/src/main/java/com/github/ambry/rest/NettyRequest.java