forked from platypush/platypush
Fabio Manganiello
6b7933cd33
This prevents multiprocessing/concurrency issues when modifying the same database file both from the main process and from the web server process
274 lines
9 KiB
Python
274 lines
9 KiB
Python
import json
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from logging import getLogger
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from queue import Queue, Empty
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from threading import Thread, Event, RLock
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from time import time
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from typing import Iterable, List, Optional
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from sqlalchemy import and_, or_
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from sqlalchemy.orm import Session, make_transient
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from platypush.context import get_bus
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from platypush.message.event.entities import EntityUpdateEvent
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from ._base import Entity, db_url
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class EntitiesEngine(Thread):
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# Processing queue timeout in seconds
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_queue_timeout = 2.0
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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._queue = Queue()
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self._should_stop = Event()
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self._entities_awaiting_flush = set()
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self._entities_cache_lock = RLock()
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self._entities_cache = {
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'by_id': {},
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'by_external_id_and_plugin': {},
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'by_name_and_plugin': {},
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}
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def _get_db(self):
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from platypush.context import get_plugin
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db = get_plugin('db')
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assert db
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return db
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def _get_cached_entity(self, entity: Entity) -> Optional[dict]:
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if entity.id:
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e = self._entities_cache['by_id'].get(entity.id)
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if e:
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return e
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if entity.external_id and entity.plugin:
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e = self._entities_cache['by_external_id_and_plugin'].get(
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(entity.external_id, entity.plugin)
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)
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if e:
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return e
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if entity.name and entity.plugin:
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e = self._entities_cache['by_name_and_plugin'].get(
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(entity.name, entity.plugin)
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)
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if e:
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return e
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@staticmethod
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def _cache_repr(entity: Entity) -> dict:
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repr_ = entity.to_json()
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repr_.pop('data', None)
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repr_.pop('meta', None)
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repr_.pop('created_at', None)
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repr_.pop('updated_at', None)
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return repr_
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def _cache_entities(self, *entities: Entity, overwrite_cache=False):
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for entity in entities:
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e = self._cache_repr(entity)
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if not overwrite_cache:
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existing_entity = self._entities_cache['by_id'].get(entity.id)
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if existing_entity:
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for k, v in existing_entity.items():
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if e.get(k) is None:
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e[k] = v
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if entity.id:
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self._entities_cache['by_id'][entity.id] = e
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if entity.external_id and entity.plugin:
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self._entities_cache['by_external_id_and_plugin'][
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(entity.external_id, entity.plugin)
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] = e
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if entity.name and entity.plugin:
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self._entities_cache['by_name_and_plugin'][
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(entity.name, entity.plugin)
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] = e
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def _populate_entity_id_from_cache(self, new_entity: Entity):
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with self._entities_cache_lock:
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cached_entity = self._get_cached_entity(new_entity)
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if cached_entity and cached_entity.get('id'):
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new_entity.id = cached_entity['id']
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if new_entity.id:
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self._cache_entities(new_entity)
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def _init_entities_cache(self):
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with self._get_db().get_session(engine=db_url) as session:
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entities = session.query(Entity).all()
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for entity in entities:
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make_transient(entity)
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with self._entities_cache_lock:
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self._cache_entities(*entities, overwrite_cache=True)
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self.logger.info('Entities cache initialized')
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def _process_event(self, entity: Entity):
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self._populate_entity_id_from_cache(entity)
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if entity.id:
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get_bus().post(EntityUpdateEvent(entity=entity))
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else:
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self._entities_awaiting_flush.add(self._to_entity_awaiting_flush(entity))
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@staticmethod
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def _to_entity_awaiting_flush(entity: Entity):
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e = entity.to_json()
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return json.dumps(
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{k: v for k, v in e.items() if k in {'external_id', 'name', 'plugin'}},
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sort_keys=True,
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)
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def post(self, *entities: Entity):
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for entity in entities:
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self._queue.put(entity)
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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 run(self):
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super().run()
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self.logger.info('Started entities engine')
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self._init_entities_cache()
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while not self.should_stop:
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msgs = []
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last_poll_time = time()
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while not self.should_stop and (
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time() - last_poll_time < self._queue_timeout
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):
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try:
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msg = self._queue.get(block=True, timeout=0.5)
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except Empty:
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continue
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if msg:
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msgs.append(msg)
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# Trigger an EntityUpdateEvent if there has
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# been a change on the entity state
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self._process_event(msg)
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if not msgs or self.should_stop:
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continue
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try:
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self._process_entities(*msgs)
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except Exception as e:
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self.logger.error('Error while processing entity updates: ' + str(e))
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self.logger.exception(e)
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self.logger.info('Stopped entities engine')
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def _get_if_exist(
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self, session: Session, entities: Iterable[Entity]
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) -> Iterable[Entity]:
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existing_entities = {
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(
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str(entity.external_id)
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if entity.external_id is not None
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else entity.name,
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entity.plugin,
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): entity
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for entity in session.query(Entity)
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.filter(
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or_(
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*[
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and_(
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Entity.external_id == entity.external_id,
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Entity.plugin == entity.plugin,
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)
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if entity.external_id is not None
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else and_(
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Entity.name == entity.name,
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Entity.type == entity.type,
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Entity.plugin == entity.plugin,
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)
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for entity in entities
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]
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)
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)
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.all()
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}
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return [
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existing_entities.get(
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(
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str(entity.external_id)
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if entity.external_id is not None
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else entity.name,
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entity.plugin,
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),
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None,
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)
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for entity in entities
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]
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def _merge_entities(
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self, entities: List[Entity], existing_entities: List[Entity]
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) -> List[Entity]:
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def merge(entity: Entity, existing_entity: Entity) -> Entity:
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columns = [col.key for col in entity.columns]
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for col in columns:
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if col == 'meta':
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existing_entity.meta = { # type: ignore
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**(existing_entity.meta or {}), # type: ignore
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**(entity.meta or {}), # type: ignore
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}
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elif col not in ('id', 'created_at'):
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setattr(existing_entity, col, getattr(entity, col))
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return existing_entity
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def entity_key(entity: Entity):
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return ((entity.external_id or entity.name), entity.plugin)
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new_entities = {}
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entities_map = {}
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# Get the latest update for each ((id|name), plugin) record
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for e in entities:
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entities_map[entity_key(e)] = e
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# Retrieve existing records and merge them
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for i, entity in enumerate(entities):
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existing_entity = existing_entities[i]
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if existing_entity:
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entity = merge(entity, existing_entity)
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new_entities[entity_key(entity)] = entity
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return list(new_entities.values())
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def _process_entities(self, *entities: Entity):
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with self._get_db().get_session(engine=db_url) as session:
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# Ensure that the internal IDs are set to null before the merge
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for e in entities:
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e.id = None # type: ignore
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existing_entities = self._get_if_exist(session, entities)
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entities = self._merge_entities(entities, existing_entities) # type: ignore
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session.add_all(entities)
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session.commit()
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for e in entities:
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session.expunge(e)
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with self._entities_cache_lock:
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for entity in entities:
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self._cache_entities(entity, overwrite_cache=True)
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entities_awaiting_flush = {*self._entities_awaiting_flush}
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for entity in entities:
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e = self._to_entity_awaiting_flush(entity)
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if e in entities_awaiting_flush:
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self._process_event(entity)
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self._entities_awaiting_flush.remove(e)
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