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# Licensed to the StackStorm, Inc ('StackStorm') under one or more |
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# contributor license agreements. See the NOTICE file distributed with |
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# this work for additional information regarding copyright ownership. |
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# The ASF licenses this file to You under the Apache License, Version 2.0 |
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# (the "License"); you may not use this file except in compliance with |
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# the License. You may obtain 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, |
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# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
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# See the License for the specific language governing permissions and |
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# limitations under the License. |
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import abc |
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import eventlet |
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import six |
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from kombu.mixins import ConsumerMixin |
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from st2common import log as logging |
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from st2common.util.greenpooldispatch import BufferedDispatcher |
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LOG = logging.getLogger(__name__) |
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class QueueConsumer(ConsumerMixin): |
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def __init__(self, connection, queues, handler): |
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self.connection = connection |
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self._dispatcher = BufferedDispatcher() |
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self._queues = queues |
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self._handler = handler |
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def shutdown(self): |
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self._dispatcher.shutdown() |
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def get_consumers(self, Consumer, channel): |
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consumer = Consumer(queues=self._queues, accept=['pickle'], callbacks=[self.process]) |
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# use prefetch_count=1 for fair dispatch. This way workers that finish an item get the next |
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# task and the work does not get queued behind any single large item. |
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consumer.qos(prefetch_count=1) |
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return [consumer] |
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def process(self, body, message): |
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try: |
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if not isinstance(body, self._handler.message_type): |
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raise TypeError('Received an unexpected type "%s" for payload.' % type(body)) |
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self._dispatcher.dispatch(self._process_message, body) |
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except: |
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LOG.exception('%s failed to process message: %s', self.__class__.__name__, body) |
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finally: |
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# At this point we will always ack a message. |
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message.ack() |
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def _process_message(self, body): |
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try: |
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self._handler.process(body) |
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except: |
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LOG.exception('%s failed to process message: %s', self.__class__.__name__, body) |
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class StagedQueueConsumer(QueueConsumer): |
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def process(self, body, message): |
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try: |
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if not isinstance(body, self._handler.message_type): |
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raise TypeError('Received an unexpected type "%s" for payload.' % type(body)) |
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processed_body = self._handler.pre_ack_process(body) |
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self._dispatcher.dispatch(self._process_message, processed_body) |
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except: |
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LOG.exception('%s failed to process message: %s', self.__class__.__name__, body) |
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finally: |
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# At this point we will always ack a message. |
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message.ack() |
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@six.add_metaclass(abc.ABCMeta) |
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class MessageHandler(object): |
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message_type = None |
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def __init__(self, connection, queues): |
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self._queue_consumer = self._get_queue_consumer(connection, queues) |
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self._consumer_thread = None |
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def start(self, wait=False): |
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LOG.info('Starting %s...', self.__class__.__name__) |
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self._consumer_thread = eventlet.spawn(self._queue_consumer.run) |
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if wait: |
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self.wait() |
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def wait(self): |
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self._consumer_thread.wait() |
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def shutdown(self): |
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LOG.info('Shutting down %s...', self.__class__.__name__) |
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self._queue_consumer.shutdown() |
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@abc.abstractmethod |
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def process(self, message): |
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pass |
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def _get_queue_consumer(self, connection, queues): |
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return QueueConsumer(connection, queues, self) |
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@six.add_metaclass(abc.ABCMeta) |
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class StagedMessageHandler(MessageHandler): |
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@abc.abstractmethod |
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def pre_ack_process(self, message): |
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pass |
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def _get_queue_consumer(self, connection, queues): |
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return StagedQueueConsumer(connection, queues, self) |
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StackStorm /
st2
