9bce85dc66
In order to reject messages before they are processed make it possible to provide a handler pair that will validate the incoming message and either reject or allow the message to be passed to the provided handler. Part of blueprint wbe-message-validation Change-Id: Ibd6ee40020c6b98283f40d5bd59e8950d63b7f71
113 lines
4.6 KiB
Python
113 lines
4.6 KiB
Python
# -*- coding: utf-8 -*-
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# Copyright (C) 2014 Yahoo! Inc. 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 logging
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from kombu import exceptions as kombu_exc
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import six
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from taskflow import exceptions as excp
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LOG = logging.getLogger(__name__)
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class TypeDispatcher(object):
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"""Receives messages and dispatches to type specific handlers."""
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def __init__(self, type_handlers):
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self._handlers = dict(type_handlers)
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self._requeue_filters = []
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def add_requeue_filter(self, callback):
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"""Add a callback that can *request* message requeuing.
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The callback will be activated before the message has been acked and
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it can be used to instruct the dispatcher to requeue the message
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instead of processing it.
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"""
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assert six.callable(callback), "Callback must be callable"
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self._requeue_filters.append(callback)
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def _collect_requeue_votes(self, data, message):
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# Returns how many of the filters asked for the message to be requeued.
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requeue_votes = 0
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for f in self._requeue_filters:
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try:
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if f(data, message):
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requeue_votes += 1
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except Exception:
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LOG.exception("Failed calling requeue filter to determine"
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" if message %r should be requeued.",
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message.delivery_tag)
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return requeue_votes
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def _requeue_log_error(self, message, errors):
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# TODO(harlowja): Remove when http://github.com/celery/kombu/pull/372
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# is merged and a version is released with this change...
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try:
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message.requeue()
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except errors as exc:
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# This was taken from how kombu is formatting its messages
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# when its reject_log_error or ack_log_error functions are
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# used so that we have a similar error format for requeuing.
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LOG.critical("Couldn't requeue %r, reason:%r",
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message.delivery_tag, exc, exc_info=True)
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else:
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LOG.debug("AMQP message %r requeued.", message.delivery_tag)
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def _process_message(self, data, message, message_type):
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handler = self._handlers.get(message_type)
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if handler is None:
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message.reject_log_error(logger=LOG,
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errors=(kombu_exc.MessageStateError,))
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LOG.warning("Unexpected message type: '%s' in message"
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" %r", message_type, message.delivery_tag)
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else:
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if isinstance(handler, (tuple, list)):
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handler, validator = handler
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try:
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validator(data)
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except excp.InvalidFormat as e:
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message.reject_log_error(
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logger=LOG, errors=(kombu_exc.MessageStateError,))
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LOG.warn("Message: %r, '%s' was rejected due to it being"
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" in an invalid format: %s",
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message.delivery_tag, message_type, e)
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return
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message.ack_log_error(logger=LOG,
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errors=(kombu_exc.MessageStateError,))
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if message.acknowledged:
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LOG.debug("AMQP message %r acknowledged.",
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message.delivery_tag)
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handler(data, message)
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def on_message(self, data, message):
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"""This method is called on incoming messages."""
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LOG.debug("Got message: %r", message.delivery_tag)
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if self._collect_requeue_votes(data, message):
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self._requeue_log_error(message,
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errors=(kombu_exc.MessageStateError,))
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else:
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try:
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message_type = message.properties['type']
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except KeyError:
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message.reject_log_error(
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logger=LOG, errors=(kombu_exc.MessageStateError,))
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LOG.warning("The 'type' message property is missing"
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" in message %r", message.delivery_tag)
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else:
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self._process_message(data, message, message_type)
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