202 lines
8.3 KiB
Python
202 lines
8.3 KiB
Python
# 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 collections
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from oslo_log import log as logging
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from oslo_utils import reflection
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from neutron_lib.callbacks import events
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from neutron_lib.callbacks import exceptions
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from neutron_lib.db import utils as db_utils
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LOG = logging.getLogger(__name__)
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class CallbacksManager(object):
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"""A callback system that allows objects to cooperate in a loose manner."""
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def __init__(self):
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self.clear()
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def subscribe(self, callback, resource, event):
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"""Subscribe callback for a resource event.
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The same callback may register for more than one event.
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:param callback: the callback. It must raise or return a boolean.
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:param resource: the resource. It must be a valid resource.
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:param event: the event. It must be a valid event.
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"""
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LOG.debug("Subscribe: %(callback)s %(resource)s %(event)s",
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{'callback': callback, 'resource': resource, 'event': event})
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callback_id = _get_id(callback)
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try:
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self._callbacks[resource][event][callback_id] = callback
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except KeyError:
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# Initialize the registry for unknown resources and/or events
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# prior to enlisting the callback.
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self._callbacks[resource][event] = {}
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self._callbacks[resource][event][callback_id] = callback
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# We keep a copy of callbacks to speed the unsubscribe operation.
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if callback_id not in self._index:
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self._index[callback_id] = collections.defaultdict(set)
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self._index[callback_id][resource].add(event)
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def unsubscribe(self, callback, resource, event):
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"""Unsubscribe callback from the registry.
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:param callback: the callback.
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:param resource: the resource.
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:param event: the event.
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"""
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LOG.debug("Unsubscribe: %(callback)s %(resource)s %(event)s",
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{'callback': callback, 'resource': resource, 'event': event})
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callback_id = self._find(callback)
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if not callback_id:
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LOG.debug("Callback %s not found", callback_id)
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return
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if resource and event:
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del self._callbacks[resource][event][callback_id]
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self._index[callback_id][resource].discard(event)
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if not self._index[callback_id][resource]:
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del self._index[callback_id][resource]
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if not self._index[callback_id]:
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del self._index[callback_id]
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else:
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value = '%s,%s' % (resource, event)
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raise exceptions.Invalid(element='resource,event', value=value)
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def unsubscribe_by_resource(self, callback, resource):
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"""Unsubscribe callback for any event associated to the resource.
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:param callback: the callback.
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:param resource: the resource.
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"""
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callback_id = self._find(callback)
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if callback_id:
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if resource in self._index[callback_id]:
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for event in self._index[callback_id][resource]:
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del self._callbacks[resource][event][callback_id]
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del self._index[callback_id][resource]
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if not self._index[callback_id]:
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del self._index[callback_id]
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def unsubscribe_all(self, callback):
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"""Unsubscribe callback for all events and all resources.
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:param callback: the callback.
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"""
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callback_id = self._find(callback)
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if callback_id:
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for resource, resource_events in self._index[callback_id].items():
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for event in resource_events:
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del self._callbacks[resource][event][callback_id]
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del self._index[callback_id]
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def publish(self, resource, event, trigger, payload=None):
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"""Notify all subscribed callback(s) with a payload.
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Dispatch the resource's event to the subscribed callbacks.
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:param resource: The resource for the event.
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:param event: The event.
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:param trigger: The trigger. A reference to the sender of the event.
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:param payload: The optional event object to send to subscribers. If
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passed this must be an instance of BaseEvent.
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:raises Invalid, CallbackFailure: The Invalid exception is raised if
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the payload object is not an instance of BaseEvent. CallbackFailure
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is raise if the underlying callback has errors.
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"""
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if payload:
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if not isinstance(payload, events.EventPayload):
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raise exceptions.Invalid(element='event payload',
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value=type(payload))
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return self.notify(resource, event, trigger, payload=payload)
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# NOTE(boden): We plan to deprecate the usage of this method and **kwargs
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# as the payload in Queens, but no warning here to avoid log flooding
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@db_utils.reraise_as_retryrequest
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def notify(self, resource, event, trigger, **kwargs):
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"""Notify all subscribed callback(s).
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Dispatch the resource's event to the subscribed callbacks.
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:param resource: The resource for the event.
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:param event: The event.
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:param trigger: The trigger. A reference to the sender of the event.
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:param kwargs: (deprecated) Unstructured key/value pairs to invoke
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the callback with. Using event objects with publish() is preferred.
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:raises CallbackFailure: CallbackFailure is raised if the underlying
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callback has errors.
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"""
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errors = self._notify_loop(resource, event, trigger, **kwargs)
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if errors:
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if event.startswith(events.BEFORE):
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abort_event = event.replace(
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events.BEFORE, events.ABORT)
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self._notify_loop(resource, abort_event, trigger, **kwargs)
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raise exceptions.CallbackFailure(errors=errors)
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if event.startswith(events.PRECOMMIT):
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raise exceptions.CallbackFailure(errors=errors)
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def clear(self):
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"""Brings the manager to a clean slate."""
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self._callbacks = collections.defaultdict(dict)
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self._index = collections.defaultdict(dict)
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def _notify_loop(self, resource, event, trigger, **kwargs):
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"""The notification loop."""
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errors = []
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callbacks = list(self._callbacks[resource].get(event, {}).items())
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LOG.debug("Notify callbacks %s for %s, %s",
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[c[0] for c in callbacks], resource, event)
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# TODO(armax): consider using a GreenPile
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for callback_id, callback in callbacks:
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try:
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callback(resource, event, trigger, **kwargs)
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except Exception as e:
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abortable_event = (
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event.startswith(events.BEFORE) or
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event.startswith(events.PRECOMMIT)
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)
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if not abortable_event:
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LOG.exception("Error during notification for "
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"%(callback)s %(resource)s, %(event)s",
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{'callback': callback_id,
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'resource': resource, 'event': event})
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else:
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LOG.debug("Callback %(callback)s raised %(error)s",
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{'callback': callback_id, 'error': e})
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errors.append(exceptions.NotificationError(callback_id, e))
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return errors
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def _find(self, callback):
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"""Return the callback_id if found, None otherwise."""
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callback_id = _get_id(callback)
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return callback_id if callback_id in self._index else None
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def _get_id(callback):
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"""Return a unique identifier for the callback."""
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# TODO(armax): consider using something other than names
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# https://www.python.org/dev/peps/pep-3155/, but this
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# might be okay for now.
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parts = (reflection.get_callable_name(callback),
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str(hash(callback)))
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return '-'.join(parts)
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