run a process slower

run_slow.py

#!/usr/bin/env python

import os
import sys
import time
import signal

QUANTUM = 0.01


class Slowdown(object):

    def __init__(self, pid):
        self.paused = False
        self.pid = pid

    def pause(self):
        if self.paused:
            return
        self.paused = True
        os.kill(self.pid, signal.SIGSTOP)

    def unpause(self):
        if not self.paused:
            return
        self.paused = False
        os.kill(self.pid, signal.SIGCONT)

    def run(self, multiplier=1):
        try:
            while True:
                self.pause()
                time.sleep(QUANTUM * multiplier)
                self.unpause()
                time.sleep(QUANTUM)
        finally:
            self.unpause()


def main():
    try:
        assert len(sys.argv) in (2, 3)
        pid = int(sys.argv[1])
        if len(sys.argv) == 3:
            multiplier = int(sys.argv[2])
        else:
            multiplier = None
    except:
        print "usage: %s <pid> [slowdown multiplier (default 1)]" % sys.argv[0]
        print "will run process pid with multiplier cycles sleeping for " \
              "every cycle running"
        sys.exit(1)
    Slowdown(pid).run(multiplier)

if __name__ == "__main__":
    main()