public void cancelSession(UUID sessionId) {
    if (myCanceledSessions.add(sessionId)) {
      final Channel channel = getConnectedChannel(sessionId);
      if (channel != null) {
        channel.writeAndFlush(CmdlineProtoUtil.toMessage(sessionId, CmdlineProtoUtil.createCancelCommand()));
      }
    }
  }
public void cancelSession(UUID sessionId)