[Help-smalltalk] CLOSE_WAIT sockets, a serious Swazoo bug

[Paolo Bonzini]

Hi Janko,

a user of GNU Smalltalk found a serious bug in Swazoo 2.2.  To reproduce 
the bug, open any Swazoo page and close the browser.  Running netstat 
will show sockets in CLOSE_WAIT state.  Repeating will show more sockets 
in this state.

The problem here is that when the client closes the socket, this 
condition is returned by SwazooStream as a SwazooStreamNoDataError 
exception; at this point, the stream should be closed on the Swazoo side 
too.

However, it is not because of this:

       [[      [ [true] whileTrue:
                      [self getAndDispatchMessages.
                      Processor yield]
               ]
            on: Error
            do: [:ex | "just ignore"] ]
       ifCurtailed: [
           (Delay forMilliseconds: 50) wait. "to finish sending, if any"
           self close] ].

Ignoring the exception causes #getAndDispatchMessages to sit forever 
waiting for I/O (not busy waiting, at least on GNU Smalltalk) while the 
socket is left open.

I changed this to

    [[[true] whileTrue:
            [self getAndDispatchMessages.
            Processor yield]]
                ifCurtailed:
                    [self close]]
        on: Error
        do: [:ex |
           (Delay forMilliseconds: 50) wait. "to finish sending, if any"
           self close]].

and it fixes the bug.

By the way, I'm not sure about the need for those delays either. 
There's one here and one in #getAndDispatchMessages.  They don't seem to 
be necessary on GNU Smalltalk.

Finally, here we're using #on:do: directly rather than the Sport 
wrapper.  I think we should do this uniformly in Swazoo for this 
particular case, since exceptions are now portable and we're relying on 
the ANSI #ifCurtailed: message anyway.

Thanks!

Paolo