server's method get called twice while client received a TimeoutException

suds

Hi :
I have modified the demo project hello's source code , and after some test I found a wierd problem.
In function sayHello of HelloI.cpp in server side

int HelloI::sayHello(int index, const Ice::Current&) const
{
  

	cout<<"call's index = "<<index<<endl;//display index passed from client
	IceUtil::ThreadControl::sleep(
		IceUtil::Time::milliSeconds( _delay ));//_delay is a pre-set value 
	

    return 1;
}

at the client side:

	int iCount = 0;
	while(!bQuit)
	{
		try
		{
			cout<<"call's index = "<<iCount <<endl;
			hPrx->sayHello(iCount);//call server's hello and tell it current index
		}
		catch( const Ice::Exception& ex)
		{
			cout<<ex.ice_name()<<endl;
		}
		iCount ++;
	}

If I set _delay in server side to 5000 ms , and in my client's code, I set the hello proxy's timeout to 2000. we'll see that the same index will appear twice on server side's console.
That is , if client detected server timed out , it'll invoke the routine again.
attached is a screen shot and the zip of source code.

michi

This shouldn't be happening because it violates at-most-once semantics. We'll have a look at this, thanks!

Michi.

benoit

Actually, this is the expected behavior for idempotent operations. If you remove the idempotent keyword from the Slice, the retry won't occur to ensure at-most-once semantics are not violated.

See the section "Idempotent Operations" here in the Ice manual for more information.

Cheers,
Benoit.

michi

Ah, yes, I should have looked at the Slice definition. Benoit is right, of course. If you mark the operation as idempotent, the retry is just what should happen.

Cheers,

Michi.

suds

Oh ! It's my mistake .
Thank you very much for your explanation