5bd31315c2
In commit d8d2ad9 we added support for notification listener endpoint methods to return REQUEUE, but if a driver does not support this we raise NotImplementedError when the application attempts to requeue a message. This requeuing behaviour might only be used by an application in unusual, exceptional circumstances and catch users by surprise. Instead, let's require the application to assert that it needs this feature in advance and raise NotImplementError at that point if the driver doesn't support it. Change-Id: Id0bb0e57d2dcc1ec7d752e98c9b1e8e48d99f35c
123 lines
4.3 KiB
Python
123 lines
4.3 KiB
Python
# Copyright 2011 OpenStack Foundation.
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# All Rights Reserved.
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# Copyright 2013 eNovance
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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 contextlib
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import itertools
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import logging
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import sys
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from oslo.messaging import localcontext
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from oslo.messaging import serializer as msg_serializer
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LOG = logging.getLogger(__name__)
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PRIORITIES = ['audit', 'debug', 'info', 'warn', 'error', 'critical', 'sample']
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class NotificationResult(object):
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HANDLED = 'handled'
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REQUEUE = 'requeue'
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class NotificationDispatcher(object):
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"""A message dispatcher which understands Notification messages.
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A MessageHandlingServer is constructed by passing a callable dispatcher
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which is invoked with context and message dictionaries each time a message
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is received.
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NotifcationDispatcher is one such dispatcher which pass a raw notification
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message to the endpoints
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"""
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def __init__(self, targets, endpoints, serializer, allow_requeue):
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self.targets = targets
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self.endpoints = endpoints
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self.serializer = serializer or msg_serializer.NoOpSerializer()
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self.allow_requeue = allow_requeue
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self._callbacks_by_priority = {}
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for endpoint, prio in itertools.product(endpoints, PRIORITIES):
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if hasattr(endpoint, prio):
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method = getattr(endpoint, prio)
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self._callbacks_by_priority.setdefault(prio, []).append(method)
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priorities = self._callbacks_by_priority.keys()
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self._targets_priorities = set(itertools.product(self.targets,
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priorities))
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def _listen(self, transport):
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return transport._listen_for_notifications(self._targets_priorities)
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@contextlib.contextmanager
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def __call__(self, incoming):
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result_wrapper = []
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yield lambda: result_wrapper.append(
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self._dispatch_and_handle_error(incoming))
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if result_wrapper[0] == NotificationResult.HANDLED:
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incoming.acknowledge()
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else:
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incoming.requeue()
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def _dispatch_and_handle_error(self, incoming):
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"""Dispatch a notification message to the appropriate endpoint method.
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:param incoming: the incoming notification message
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:type ctxt: IncomingMessage
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"""
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try:
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return self._dispatch(incoming.ctxt, incoming.message)
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except Exception:
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# sys.exc_info() is deleted by LOG.exception().
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exc_info = sys.exc_info()
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LOG.error('Exception during message handling',
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exc_info=exc_info)
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return NotificationResult.HANDLED
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def _dispatch(self, ctxt, message):
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"""Dispatch an RPC message to the appropriate endpoint method.
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:param ctxt: the request context
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:type ctxt: dict
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:param message: the message payload
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:type message: dict
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"""
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ctxt = self.serializer.deserialize_context(ctxt)
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publisher_id = message.get('publisher_id')
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event_type = message.get('event_type')
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priority = message.get('priority', '').lower()
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if priority not in PRIORITIES:
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LOG.warning('Unknown priority "%s"' % priority)
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return
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payload = self.serializer.deserialize_entity(ctxt,
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message.get('payload'))
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for callback in self._callbacks_by_priority.get(priority, []):
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localcontext.set_local_context(ctxt)
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try:
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ret = callback(ctxt, publisher_id, event_type, payload)
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ret = NotificationResult.HANDLED if ret is None else ret
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if self.allow_requeue and ret == NotificationResult.REQUEUE:
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return ret
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finally:
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localcontext.clear_local_context()
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return NotificationResult.HANDLED
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