I'm using a recipe that relies on SIGALRM to set alarm interrupt -- Using module 'subprocess' with timeout

The problem is that I have more than one Python script using signal.ALARM process to set time-outs, and only the latest alarm gets called. What is a good way to improve this multiple Python functions setting time-outs?

Except for simple, quick hacks, avoid SIGALRM. It's a very old, limited mechanism, not suited to anything more complex: you can only set a single alarm, and it interrupts any system call at the time rather than just the one you intend to interrupt.

It's much cleaner to use a timeout thread to kill the process, for example:

import subprocess, signal, os, threading, errno
from contextlib import contextmanagerclass TimeoutThread(object):def __init__(self, seconds):self.seconds = secondsself.cond = threading.Condition()self.cancelled = Falseself.thread = threading.Thread(target=self._wait)def run(self):"""Begin the timeout."""self.thread.start()def _wait(self):with self.cond:self.cond.wait(self.seconds)if not self.cancelled:self.timed_out()def cancel(self):"""Cancel the timeout, if it hasn't yet occured."""with self.cond:self.cancelled = Trueself.cond.notify()self.thread.join()def timed_out(self):"""The timeout has expired."""raise NotImplementedErrorclass KillProcessThread(TimeoutThread):def __init__(self, seconds, pid):super(KillProcessThread, self).__init__(seconds)self.pid = piddef timed_out(self):try:os.kill(self.pid, signal.SIGKILL)except OSError as e:# If the process is already gone, ignore the error.if e.errno not in (errno.EPERM, errno. ESRCH):raise e@contextmanager
def processTimeout(seconds, pid):timeout = KillProcessThread(seconds, pid)timeout.run()try:yieldfinally:timeout.cancel()def example():proc = subprocess.Popen(["sleep", "5"], stdin=subprocess.PIPE, stdout=subprocess.PIPE)with processTimeout(1, proc.pid):print proc.communicate()resultcode = proc.wait()if resultcode < 0:print "error: %i" % resultcodeif __name__ == '__main__':example()

Depending on what you're timing out, you may want to use a lighter signal than SIGKILL to allow the timing-out process to clean up after itself.