136 lines
5.0 KiB
Python
136 lines
5.0 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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pool=None):
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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.pool = pool
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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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pool=self.pool)
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@contextlib.contextmanager
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def __call__(self, incoming, executor_callback=None):
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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, executor_callback))
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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, executor_callback):
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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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executor_callback)
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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, executor_callback=None):
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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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metadata = {
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'message_id': message.get('message_id'),
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'timestamp': message.get('timestamp')
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}
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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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if executor_callback:
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ret = executor_callback(callback, ctxt, publisher_id,
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event_type, payload, metadata)
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else:
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ret = callback(ctxt, publisher_id, event_type, payload,
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metadata)
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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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