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# Licensed under the Apache License, Version 2.0 (the "License"); you may
# not use this file except in compliance with the License. You may obtain
# a copy of the License at
#
# http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
# WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
# License for the specific language governing permissions and limitations
# under the License.
import collections
from oslo_log import log as logging
from oslo_utils import reflection
from neutron_lib.callbacks import events
from neutron_lib.callbacks import exceptions
from neutron_lib.callbacks import priority_group
from neutron_lib.db import utils as db_utils
LOG = logging.getLogger(__name__)
PriorityCallbacks = collections.namedtuple(
'PriorityCallbacks', ['priority', 'pri_callbacks', 'cancellable'])
Callback = collections.namedtuple(
'Callback', ['id', 'method', 'cancellable'])
class CallbacksManager:
"""A callback system that allows objects to cooperate in a loose manner."""
def __init__(self):
self.clear()
def subscribe(self, callback, resource, event,
priority=priority_group.PRIORITY_DEFAULT,
cancellable=False):
"""Subscribe callback for a resource event.
The same callback may register for more than one event.
:param callback: the callback. It must raise or return a boolean.
:param resource: the resource. It must be a valid resource.
:param event: the event. It must be a valid event.
:param priority: the priority. Callbacks are sorted by priority
to be called. Smaller one is called earlier.
:param cancellable: if the callback is "cancellable", in case of
returning an exception, the callback manager will
raise a ``CallbackFailure`` exception.
"""
LOG.debug("Subscribe: %(callback)s %(resource)s %(event)s "
"%(priority)d, %(cancellable)s",
{'callback': callback, 'resource': resource, 'event': event,
'priority': priority, 'cancellable': cancellable})
callback_id = _get_id(callback)
pri_callbacks_list = self._callbacks[resource].setdefault(event, [])
for pri_callbacks in pri_callbacks_list:
if pri_callbacks.priority == priority:
pri_callbacks = pri_callbacks.pri_callbacks
break
else:
pri_callbacks = {}
pri_callbacks_list.append(
PriorityCallbacks(priority, pri_callbacks, cancellable))
pri_callbacks_list.sort(key=lambda x: x.priority)
pri_callbacks[callback_id] = callback
# We keep a copy of callbacks to speed the unsubscribe operation.
if callback_id not in self._index:
self._index[callback_id] = collections.defaultdict(set)
self._index[callback_id][resource].add(event)
def _del_callback(self, pri_callbacks, callback_id):
for pri_callback in pri_callbacks:
if callback_id in pri_callback.pri_callbacks:
del pri_callback.pri_callbacks[callback_id]
if not pri_callback.pri_callbacks:
pri_callbacks.remove(pri_callback)
break
def unsubscribe(self, callback, resource, event):
"""Unsubscribe callback from the registry.
:param callback: the callback.
:param resource: the resource.
:param event: the event.
"""
LOG.debug("Unsubscribe: %(callback)s %(resource)s %(event)s",
{'callback': callback, 'resource': resource, 'event': event})
callback_id = self._find(callback)
if not callback_id:
LOG.debug("Callback %s not found", callback_id)
return
if resource and event:
self._del_callback(self._callbacks[resource][event], callback_id)
self._index[callback_id][resource].discard(event)
if not self._index[callback_id][resource]:
del self._index[callback_id][resource]
if not self._index[callback_id]:
del self._index[callback_id]
else:
value = '{},{}'.format(resource, event)
raise exceptions.Invalid(element='resource,event', value=value)
def unsubscribe_by_resource(self, callback, resource):
"""Unsubscribe callback for any event associated to the resource.
:param callback: the callback.
:param resource: the resource.
"""
callback_id = self._find(callback)
if callback_id:
if resource in self._index[callback_id]:
for event in self._index[callback_id][resource]:
self._del_callback(self._callbacks[resource][event],
callback_id)
del self._index[callback_id][resource]
if not self._index[callback_id]:
del self._index[callback_id]
def unsubscribe_all(self, callback):
"""Unsubscribe callback for all events and all resources.
:param callback: the callback.
"""
callback_id = self._find(callback)
if callback_id:
for resource, resource_events in self._index[callback_id].items():
for event in resource_events:
self._del_callback(self._callbacks[resource][event],
callback_id)
del self._index[callback_id]
@db_utils.reraise_as_retryrequest
def publish(self, resource, event, trigger, payload=None):
"""Notify all subscribed callback(s) with a payload.
Dispatch the resource's event to the subscribed callbacks.
:param resource: The resource for the event.
:param event: The event.
:param trigger: The trigger. A reference to the sender of the event.
:param payload: The optional event object to send to subscribers. If
passed this must be an instance of BaseEvent.
:raises neutron_lib.callbacks.exceptions.Invalid: if
the payload object is not an instance of BaseEvent.
:raises CallbackFailure: if the underlying callback has errors.
"""
if payload:
if not isinstance(payload, events.EventPayload):
raise exceptions.Invalid(element='event payload',
value=type(payload))
errors = self._notify_loop(resource, event, trigger, payload)
if errors:
if event.startswith(events.BEFORE):
abort_event = event.replace(
events.BEFORE, events.ABORT)
self._notify_loop(resource, abort_event, trigger, payload)
raise exceptions.CallbackFailure(errors=errors)
if (event.startswith(events.PRECOMMIT) or
any(error.is_cancellable for error in errors)):
raise exceptions.CallbackFailure(errors=errors)
def clear(self):
"""Brings the manager to a clean slate."""
self._callbacks = collections.defaultdict(dict)
self._index = collections.defaultdict(dict)
def _notify_loop(self, resource, event, trigger, payload):
"""The notification loop."""
errors = []
callbacks = []
for pri_callbacks in self._callbacks[resource].get(event, []):
for cb_id, cb_method in pri_callbacks.pri_callbacks.items():
cb = Callback(cb_id, cb_method, pri_callbacks.cancellable)
callbacks.append(cb)
resource_id = getattr(payload, "resource_id", None)
LOG.debug("Publish callbacks %s for %s (%s), %s",
[c.id for c in callbacks], resource, resource_id, event)
# TODO(armax): consider using a GreenPile
for callback in callbacks:
try:
callback.method(resource, event, trigger, payload=payload)
except Exception as e:
if not (events.is_cancellable_event(event) or
callback.cancellable):
LOG.exception("Error during notification for "
"%(callback)s %(resource)s, %(event)s",
{'callback': callback.id,
'resource': resource, 'event': event})
else:
LOG.debug("Callback %(callback)s raised %(error)s",
{'callback': callback.id, 'error': e})
errors.append(exceptions.NotificationError(
callback.id, e, cancellable=callback.cancellable))
return errors
def _find(self, callback):
"""Return the callback_id if found, None otherwise."""
callback_id = _get_id(callback)
return callback_id if callback_id in self._index else None
def _get_id(callback):
"""Return a unique identifier for the callback."""
# TODO(armax): consider using something other than names
# https://www.python.org/dev/peps/pep-3155/, but this
# might be okay for now.
parts = (reflection.get_callable_name(callback),
str(hash(callback)))
return '-'.join(parts)
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