David <[EMAIL PROTECTED]> wrote: > Would it be possible for a 3rd-party threading library to an > 'interruptible' version of Queue? > > The same methods as the normal Queue, but when you call a new .kill() > method on the queue, all the threads locking on the queue get a > "QueueKilled" exception thrown. > > It might be as simple as a Queue wrapper where .kill() adds a speciall > Killed value to the queue, and the .get() wrapper throws a QueueKilled > exception (after re-putting Killed) when it reads Killed.
There seem to me to be 2 basic types of threads - I'll call them client threads and server threads. A client thread listens on a Queue for its instructions and replies via a different Queue, or via Queues passed in in its instructions. That kind of thread can easily have an instruction which means quit. When it isn't processing instructions there is a nice clean moment for it to quit. However if the processing takes a long time then there will be a long wait for the thread to die. This is the scenario described above. The server type thread is processing all the time. Every now and again it sends its results via a Queue. An example of this type of thread might be one listening on a socket. This type of thread has no nice moment to listen for instructions to quit as it might well be blocked on something else (eg listening to a socket). To make this type of thread kill nicely you have to go back to breaking up your work into chunks (eg polling the socket asynchronously) and polling the command queue to wait for your quit instruction which is wastefull of CPU resources. So it seems to me that there isn't a good solution to killing python threads of either type, other than coding them carefully and checking for quit instructions regularly. You can kill them using the internal python API and ctypes, but you run the risk of leaving things in an inconsistent state which is why that API isn't exposed. Here is an attempt at a killable thread http://aspn.activestate.com/ASPN/Cookbook/Python/Recipe/496960 and http://sebulba.wikispaces.com/recipe+thread2 Read the caveats! -- Nick Craig-Wood <[EMAIL PROTECTED]> -- http://www.craig-wood.com/nick -- http://mail.python.org/mailman/listinfo/python-list
