126 lines
4.3 KiB
Python
126 lines
4.3 KiB
Python
# Copyright (c) 2016 Mirantis, Inc.
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# All Rights Reserved.
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#
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# Licensed under the Apache License, Version 2.0 (the "License"); you may
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# not use this file except in compliance with the License. You may obtain
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# a copy of the License at
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#
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# http://www.apache.org/licenses/LICENSE-2.0
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#
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# Unless required by applicable law or agreed to in writing, software
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# distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
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# WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
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# License for the specific language governing permissions and limitations
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# under the License.
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import abc
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from oslo_log import log as logging
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from kuryr_kubernetes.handlers import base as h_base
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LOG = logging.getLogger(__name__)
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class Dispatcher(h_base.EventHandler):
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"""Dispatches events to registered handlers.
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Dispatcher serves as both multiplexer and filter for dispatching events
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to multiple registered handlers based on the event content and
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predicates provided during the handler registration.
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"""
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def __init__(self):
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self._registry = {}
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def register(self, key_fn, key, handler):
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"""Adds handler to the registry.
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`key_fn` and `key` constitute the `key_fn(event) == key` predicate
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that determines if the `handler` should be called for a given `event`.
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:param key_fn: function that will be called for each event to
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determine the event `key`
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:param key: value to match against the result of `key_fn` function
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that determines if the `handler` should be called for an
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event
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:param handler: `callable` object that would be called if the
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conditions specified by `key_fn` and `key` are met
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"""
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key_group = self._registry.setdefault(key_fn, {})
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handlers = key_group.setdefault(key, [])
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handlers.append(handler)
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def __call__(self, event, *args, **kwargs):
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handlers = set()
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for key_fn, key_group in self._registry.items():
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key = key_fn(event)
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handlers.update(key_group.get(key, ()))
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obj = event.get('object', {})
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obj_meta = obj.get('metadata', {})
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LOG.debug("%d handler(s) available for event %s %s:%s/%s (uid: %s)",
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len(handlers), event.get('type'), obj.get('kind'),
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obj_meta.get('namespace'), obj_meta.get('name'),
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obj_meta.get('uid'))
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for handler in handlers:
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handler(event, *args, **kwargs)
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class EventConsumer(h_base.EventHandler, metaclass=abc.ABCMeta):
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"""Consumes events matching specified predicates.
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EventConsumer is an interface for all event handlers that are to be
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registered by the `EventPipeline`.
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"""
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def __init__(self):
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super(EventConsumer, self).__init__()
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@abc.abstractproperty
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def consumes(self):
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"""Predicates determining events supported by this handler.
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:return: `dict` object containing {key_fn: key} predicates to be
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used by `Dispatcher.register`
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"""
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raise NotImplementedError()
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class EventPipeline(h_base.EventHandler, metaclass=abc.ABCMeta):
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"""Serves as an entry-point for event handling.
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Implementing subclasses should override `_wrap_dispatcher` and/or
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`_wrap_consumer` methods to sanitize the consumers passed to `register`
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(i.e. to satisfy the `Watcher` requirement that the event handler does
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not raise exceptions) and to add features like asynchronous event
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processing or retry-on-failure functionality.
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"""
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def __init__(self):
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self._dispatcher = Dispatcher()
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self._handler = self._wrap_dispatcher(self._dispatcher)
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def register(self, consumer):
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"""Adds handler to the registry.
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:param consumer: `EventConsumer`-type object
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"""
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handler = self._wrap_consumer(consumer)
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for key_fn, key in consumer.consumes.items():
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self._dispatcher.register(key_fn, key, handler)
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def __call__(self, event, *args, **kwargs):
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self._handler(event, *args, **kwargs)
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@abc.abstractmethod
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def _wrap_dispatcher(self, dispatcher):
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raise NotImplementedError()
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@abc.abstractmethod
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def _wrap_consumer(self, consumer):
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raise NotImplementedError()
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