Jacek Poplawski had written: >> I am going to write python script which will read python >> command from socket, run it and return some values back to >> socket. >> >> My problem is, that I need some timeout.
Jacek Poplawski wrote: > After reading more archive I think that solution may be to raise an > Exception after timeout, but how to do it portable? Python allows any thread to raise a KeyboardInterrupt in the main thread (see thread.interrupt_main), but I don't think there is any standard facility to raise an exception in any other thread. I also believe, and hope, there is no support for lower- level killing of threads; doing so is almost always a bad idea. At arbitrary kill-times, threads may have important business left to do, such as releasing locks, closing files, and other kinds of clean-up. Processes look like a better choice than threads here. Any decent operating system will put a deceased process's affairs in order. Anticipating the next issues: we need to spawn and connect to the various worker processes, and we need to time-out those processes. First, a portable worker-process timeout: In the child process, create a worker daemon thread, and let the main thread wait until either the worker signals that it is done, or the timeout duration expires. As the Python Library Reference states in section 7.5.6: A thread can be flagged as a "daemon thread". The significance of this flag is that the entire Python program exits when only daemon threads are left. The following code outlines the technique: import threading work_is_done = threading.Event() def work_to_do(*args): # ... Do the work. work_is_done.set() if __name__ == '__main__': # ... Set stuff up. worker_thread = threading.Thread( target = work_to_do, args = whatever_params) worker_thread.setDaemon(True) worker_thread.start() work_is_done.wait(timeout_duration) Next, how do we connect the clients to the worker processes? If Unix-only is acceptable, we can set up the accepting socket, and then fork(). The child processes can accept() incomming connections on its copy of the socket. Be aware that select() on the process-shared socket is tricky, in that that the socket can select as readable, but the accept() can block because some other processes took the connection. If we need to run on Windows (and Unix), we can have one main process handle the socket connections, and pipe the data to and from worker processes. See the popen2 module in the Python Standard Library. -- --Bryan -- http://mail.python.org/mailman/listinfo/python-list