@Override
 public void failed(RpcException ex) {
   acct.decrement();
   fail("Failure while sending single result.", ex);
 }
 @Override
 public void success(Ack value, ByteBuf buffer) {
   acct.decrement();
 }
 public SingleListener() {
   acct = new SendingAccountor();
   acct.increment();
   acct.increment();
 }