8b7d2c8a93
This patch is the first one of a series of patches improving how the L3 agents update the router HA state to the Neutron server. This patch partially reverts the previous patch [1]. When the batch notifier sends events, it calls the callback method passed during the initialization, in this case AgentMixin.notify_server. The batch notifier spawns a new thread in charge of sending the notifications and then wait the specified "batch_interval" time. If the callback method is not synchronous with the notify thread execution (what [1] implemented), the thread can finish while the RPC client is still sending the HA router states. If another HA state update is received, then both updates can be executed at the same time. It is possible then that a new router state can be overwritten with an old one still not sent or processed. The batch notifier is refactored, to improve what initally was implemented [2] and then updated [3]. Currently, each new event thread can update the "pending_events" list. Then, a new thread is spawned to process this event list. This thread decouples the current execution from the calling thread, making the event processing a non-blocking process. But with the current implementation, each new process will spawn a new thread, synchronized with the previous and new ones (using a synchronized decorator). That means, during the batch interval time, the system can have as many threads waiting as new events received. Those threads will end secuentially when the previous threads end the batch interval sleep time. Instead of this, this patch receives and enqueue each new event and allows only one thread to be alive while processing the event list. If at the end of the processing loop new events are stored, the thread will process then. [1] I3f555a0c78fbc02d8214f12b62c37d140bc71da1 [2] I2f8cf261f48bdb632ac0bd643a337290b5297fce [3] I82f403441564955345f47877151e0c457712dd2f Partial-Bug: #1837635 Change-Id: I20cfa1cf5281198079f5e0dbf195755abc919581
70 lines
2.7 KiB
Python
70 lines
2.7 KiB
Python
# 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 threading
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import eventlet
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from neutron.common import utils
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class BatchNotifier(object):
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def __init__(self, batch_interval, callback):
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self._pending_events = eventlet.Queue()
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self.callback = callback
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self.batch_interval = batch_interval
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self._mutex = threading.Lock()
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def queue_event(self, event):
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"""Called to queue sending an event with the next batch of events.
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Sending events individually, as they occur, has been problematic as it
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can result in a flood of sends. Previously, there was a loopingcall
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thread that would send batched events on a periodic interval. However,
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maintaining a persistent thread in the loopingcall was also
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problematic.
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This replaces the loopingcall with a mechanism that creates a
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short-lived thread on demand whenever an event is queued. That thread
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will check if the lock is released, send all queued events and then
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sleep for 'batch_interval' seconds. If at the end of this sleep time,
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other threads have added new events to the event queue, the same thread
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will process them.
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At the same time, other threads will be able to add new events to the
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queue and will spawn new "synced_send" threads to process them. But if
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the mutex is locked, the spawned thread will end immediately.
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:param event: the event that occurred.
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"""
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if not event:
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return
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self._pending_events.put(event)
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def synced_send():
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if not self._mutex.locked():
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with self._mutex:
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while not self._pending_events.empty():
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self._notify()
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# sleeping after send while holding the lock allows
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# subsequent events to batch up
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eventlet.sleep(self.batch_interval)
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utils.spawn_n(synced_send)
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def _notify(self):
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batched_events = []
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while not self._pending_events.empty():
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batched_events.append(self._pending_events.get())
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self.callback(batched_events)
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