use goless to implement monitor

monitor.py

import goless
import time
import gevent
from gevent import monkey
monkey.patch_all()

def time_after(seconds):
    c = goless.chan()
    def _fn():
        gevent.sleep(seconds)
        c.send(True)
    goless.go(_fn)
    return c

class Monitor(object):
    def __init__(self):
        self._chan = goless.chan(0)
        self._tasks = []
        self._running = True
        self._cycle = 0.5
        goless.go(self._drain)

    def start(self):
        self._chan.send(True)

    def stop(self):
        self._chan.send(False)

    def addfunc(self, func, *args, **kwargs):
        self._tasks.append([func, args, kwargs])

    def _drain(self):
        while True:
            cases = [goless.rcase(self._chan), goless.rcase(time_after(self._cycle))]
            chosen, is_start = goless.select(cases)
            if chosen is cases[0]:
                self._running = is_start
                continue
            if not self._running:
                continue
            for task in self._tasks:
                func, args, kwargs = task
                goless.go(func, *args, **kwargs)

m = Monitor()
def say(msg = 'hello'):
    print 'say:', msg

m.addfunc(say, 'hi')
m.start()
gevent.sleep(4)
m.stop()