class for managing multiple servers in gevent

ServerRack.py

class ServerRack(object):
    """Manages multiple gevent Servers. Works with anything that has
    start() and stop() methods.

    Adapted from:
        https://gist.github.com/1008826
    """

    def __init__(self):
        self._servers = []
        self._stop_event = gevent.event.Event()
        self._stop_event.set()

    def add(self, server):
        self._servers.append(server)

    def start(self):
        started = []
        self._stop_event.clear()
        try:
            for server in self._servers:
                server.start()
                started.append(server)
        except:
            self.stop(servers=started)
            raise

    def stop(self, timeout=None, servers=None):
        if not servers:
            servers = self._servers[:]
        self._stop_event.set()
        for server in servers:
            try:
                server.stop(timeout=timeout)
            except:
                if hasattr(server, 'loop'): # gevent >= 1.0
                    server.loop.handle_error(server.stop, *sys.exc_info())
                else: # gevent <= 0.13
                    import traceback
                    traceback.print_exc()

    def serve_forever(self, stop_timeout=None):
        self.start()
        try:
            self._stop_event.wait()
        finally:
            gevent.spawn(self.stop, timeout=stop_timeout).join()


class GreenletService(object):

    def __init__(self, func, args=None, kwargs=None, spawn=None):
        self.func, self.args, self.kwargs = func, args or (), kwargs or {}
        self.spawn = spawn or gevent.spawn

    def start(self):
        self.greenlet = self.spawn(self.func, *self.args, **self.kwargs)

    def stop(self, timeout=None):
        self.greenlet.kill()