larigira/larigira/eventutils.py

import gevent


class ParentedLet(gevent.Greenlet):
    """
    ParentedLet is just a helper subclass that will help you when your
    greenlet main duty is to "signal" things to a parent_queue.

    It won't save you much code, but "standardize" messages and make explicit
    the role of that greenlet
    """

    def __init__(self, queue):
        gevent.Greenlet.__init__(self)
        self.parent_queue = queue
        self.parent_greenlet = None
        self.tracker = None  # set this to recognize easily

    def parent_msg(self, kind, *args):
        return {
            "emitter": self,
            "class": self.__class__.__name__,
            "tracker": self.tracker,
            "kind": kind,
            "args": args,
        }

    def send_to_parent(self, kind, *args):
        self.parent_queue.put(self.parent_msg(kind, *args))

    def _run(self):
        if not hasattr(self, "do_business"):
            raise Exception(
                "do_business method not implemented by %s" % self.__class__.__name__
            )
        for msg in self.do_business():
            self.send_to_parent(*msg)


class Timer(ParentedLet):
    """continously sleeps some time, then send a "timer" message to parent"""

    def __init__(self, milliseconds, queue):
        ParentedLet.__init__(self, queue)
        self.ms = milliseconds

    def parent_msg(self, kind, *args):
        msg = ParentedLet.parent_msg(self, kind, *args)
        msg["period"] = self.ms
        return msg

    def do_business(self):
        while True:
            gevent.sleep(self.ms / 1000.0)
            yield ("timer",)