[Tutor] Threading + socket server (blocking IO)

[Liam Clarke]

Hi,


Just poking at threads, I'm contemplating doing something that I think
may be a very dumb thing to do, or it may work fine.

In the following code -


import threading
import Queue
import reg
import msvcrt

class ParseThread(threading.Thread):

    def __init__(self, Q, parser):
        self.Q = Q
        self.parser = parser
        self.sendIt = False
        threading.Thread.__init__(self)

    def run(self):
        while True:
            if self.sendIt:
                parser.send_data()
                self.sendIt = False
            try:
                data = self.Q.get(False)
                self.parser.check(data)
            except Empty:
                continue


if __name__ == "__main__":

    Q = Queue.Queue()
    parser = reg.Parser()

    t1 = ParseThread(Q, parser)
    t1.start()

    while True:
        if msvcrt.kbhit():
            if msvcrt.getch()=="S":
                t1.sendIt = True


It's the sendIt attribute in t1. Is setting an attribute of a running
thread a very bad thing, or a just be careful thing? The only usages
for the attribute are as above, if it's set to True. the thread calls
a method of the parser object, and then resets it to False.

I can see an interesting collision if an external source sets
self.sendIt to True as the thread sets it to False.

I intend to use this with a timer, so that very x minutes, the
attribute is changed, which hopefully sidesteps that particular
collision.

But yes, very unfamiliar territory, and I'm worried about sowing the
seeds of my own destruction by being too clever/dumb.

Regards,

Liam Clarke

On 2/19/06, Liam Clarke <ml.cyresse at gmail.com> wrote:
> Thanks Kent, I'll try swapping it around and see how it goes.
>
> As for the setDaemon, my apologies. There's a
>
> while True:
>     if msvcrt.kbhit():
>         break
>
> loop afterwards, so at a keypress it exits, hence the daemon stuff.
>
>
> On 2/19/06, Kent Johnson <kent37 at tds.net> wrote:
> > Liam Clarke wrote:
> > > Hi,
> > >
> > > Just coming back to the server end of things. Kent, could I please ask
> > > you to confirm that I'm not doing anything abnormal with the
> > > ThreadingMixIn? The code is here at rafb:
> > > http://www.rafb.net/paste/results/915JVm90.html
> > >
> > > Basically, when I test it using a script to generate the datagrams via
> > > localhost, the server misses anywhere between 200 - 400 datagrams out
> > > of 1041.
> >
> > I don't have time for a detailed response but it looks OK except
> > ThreadingMixin needs to be the first base class because it overrides a
> > method of UDPServer. It turns out there is a class
> > SocketServer.ThreadingUDPServer that does this.
> >
> > Also I'm surprised the program stays running - ISTM with the server
> > thread marked daemon and the main thread exiting the program should exit...
> >
> > Kent
> >
> >
>