a68d40bf02
Instead of recreating a dispatcher in the server
and executor objects use a common dispatcher that
is shared between them. It will dispatch based on
the message type received into a provided dict of
dispatch handler callbacks.
It also can generically requeue messages and can
reject messages if they are missing key required
message properties ('type' in the current case).
Part of blueprint wbe-message-validation
Change-Id: I8320f4707183f36e6a69f0552cf62f99a5467b7e
121 lines
4.6 KiB
Python
121 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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import socket
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import threading
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import kombu
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import six
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from taskflow.engines.worker_based import dispatcher
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LOG = logging.getLogger(__name__)
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# NOTE(skudriashev): A timeout of 1 is often used in environments where
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# the socket can get "stuck", and is a best practice for Kombu consumers.
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DRAIN_EVENTS_PERIOD = 1
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class Proxy(object):
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"""A proxy processes messages from/to the named exchange."""
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def __init__(self, topic, exchange_name, type_handlers, on_wait=None,
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**kwargs):
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self._topic = topic
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self._exchange_name = exchange_name
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self._on_wait = on_wait
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self._running = threading.Event()
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self._url = kwargs.get('url')
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self._transport = kwargs.get('transport')
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self._transport_opts = kwargs.get('transport_options')
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self._dispatcher = dispatcher.TypeDispatcher(type_handlers)
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self._dispatcher.add_requeue_filter(
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# NOTE(skudriashev): Process all incoming messages only if proxy is
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# running, otherwise requeue them.
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lambda data, message: not self.is_running)
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self._drain_events_timeout = DRAIN_EVENTS_PERIOD
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if self._transport == 'memory' and self._transport_opts:
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polling_interval = self._transport_opts.get('polling_interval')
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if polling_interval:
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self._drain_events_timeout = polling_interval
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# create connection
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self._conn = kombu.Connection(self._url, transport=self._transport,
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transport_options=self._transport_opts)
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# create exchange
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self._exchange = kombu.Exchange(name=self._exchange_name,
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durable=False,
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auto_delete=True)
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@property
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def is_running(self):
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"""Return whether the proxy is running."""
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return self._running.is_set()
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def _make_queue(self, name, exchange, **kwargs):
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"""Make named queue for the given exchange."""
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return kombu.Queue(name="%s_%s" % (self._exchange_name, name),
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exchange=exchange,
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routing_key=name,
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durable=False,
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auto_delete=True,
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**kwargs)
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def publish(self, msg, routing_key, **kwargs):
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"""Publish message to the named exchange with given routing key."""
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LOG.debug("Sending %s", msg)
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if isinstance(routing_key, six.string_types):
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routing_keys = [routing_key]
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else:
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routing_keys = routing_key
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with kombu.producers[self._conn].acquire(block=True) as producer:
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for routing_key in routing_keys:
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queue = self._make_queue(routing_key, self._exchange)
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producer.publish(body=msg.to_dict(),
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routing_key=routing_key,
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exchange=self._exchange,
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declare=[queue],
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type=msg.TYPE,
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**kwargs)
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def start(self):
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"""Start proxy."""
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LOG.info("Starting to consume from the '%s' exchange.",
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self._exchange_name)
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with kombu.connections[self._conn].acquire(block=True) as conn:
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queue = self._make_queue(self._topic, self._exchange, channel=conn)
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with conn.Consumer(queues=queue,
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callbacks=[self._dispatcher.on_message]):
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self._running.set()
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while self.is_running:
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try:
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conn.drain_events(timeout=self._drain_events_timeout)
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except socket.timeout:
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pass
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if self._on_wait is not None:
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self._on_wait()
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def wait(self):
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"""Wait until proxy is started."""
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self._running.wait()
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def stop(self):
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"""Stop proxy."""
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self._running.clear()
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