83 lines
2.7 KiB
Python
83 lines
2.7 KiB
Python
from logging import getLogger
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from threading import Thread, Event
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from platypush.context import get_bus
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from platypush.entities import Entity
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from platypush.message.event.entities import EntityUpdateEvent
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from platypush.utils import set_thread_name
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# pylint: disable=no-name-in-module
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from platypush.entities._engine.queue import EntitiesQueue
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from platypush.entities._engine.repo import EntitiesRepository
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class EntitiesEngine(Thread):
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"""
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This thread runs the "brain" of the entities data persistence logic.
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Its purpose is to:
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1. Consume entities from a queue (synchronized with the upstream
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integrations that produce/handle them). The producer/consumer model
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ensure that only this thread writes to the database, packs events
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together (preventing excessive writes and throttling events), and
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prevents race conditions when SQLite is used.
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2. Merge any existing entities with their newer representations.
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3. Update the entities taxonomy.
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4. Persist the new state to the entities database.
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5. Trigger events for the updated entities.
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"""
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def __init__(self):
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obj_name = self.__class__.__name__
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super().__init__(name=obj_name)
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self.logger = getLogger(name=obj_name)
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self._should_stop = Event()
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self._queue = EntitiesQueue(stop_event=self._should_stop)
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self._repo = EntitiesRepository()
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def post(self, *entities: Entity):
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self._queue.put(*entities)
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@property
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def should_stop(self) -> bool:
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return self._should_stop.is_set()
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def stop(self):
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self._should_stop.set()
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def notify(self, *entities: Entity):
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"""
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Trigger an EntityUpdateEvent if the entity has been persisted, or queue
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it to the list of entities whose notifications will be flushed when the
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session is committed.
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"""
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for entity in entities:
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get_bus().post(EntityUpdateEvent(entity=entity))
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def run(self):
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super().run()
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set_thread_name('entities')
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self.logger.info('Started entities engine')
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while not self.should_stop:
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# Get a batch of entity updates forwarded by other integrations
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entities = self._queue.get()
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if not entities or self.should_stop:
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continue
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# Store the batch of entities
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try:
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entities = self._repo.save(*entities)
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except Exception as e:
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self.logger.error('Error while processing entity updates: %s', e)
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self.logger.exception(e)
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continue
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# Trigger EntityUpdateEvent events
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self.notify(*entities)
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self.logger.info('Stopped entities engine')
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