Just compared the pymongo_base.py in ceilometer/storage btween icehouse(https://github.com/openstack/ceilometer/blob/stable/icehouse/ceilometer/storage/pymongo_base.py) and juno release(https://github.com/openstack/ceilometer/blob/stable/juno/ceilometer/storage/pymongo_base.py), there is no such method called get_events defined in icehouse version while juno version has the following definition.

def get_events(self, event_filter):
        """Return an iter of models.Event objects.

        :param event_filter: storage.EventFilter object, consists of filters
                             for events that are stored in database.
        """
        q = pymongo_utils.make_events_query_from_filter(event_filter)
        for event in self.db.event.find(q):
            traits = []
            for trait in event['traits']:
                traits.append(models.Trait(name=trait['trait_name'],
                                           dtype=int(trait['trait_type']),
                                           value=trait['trait_value']))
            yield models.Event(message_id=event['_id'],
                               event_type=event['event_type'],
                               generated=event['timestamp'],
                               traits=traits)

This should explain the why the NotImplementedError('Events not implemented.') raised

The fix might be add the get_events method in your icehouse version or just upgrade to the latest juno release.

Hope that helps!

Vic