Using a different SQLite database for entities

This prevents multiprocessing/concurrency issues when modifying the same
database file both from the main process and from the web server process

platypush/entities/__init__.py

@@ -1,7 +1,7 @@
 import warnings
 from typing import Collection, Optional
 
-from ._base import Entity, get_entities_registry
+from ._base import Entity, get_entities_registry, db_url
 from ._engine import EntitiesEngine
 from ._registry import manages, register_entity_plugin, get_plugin_entity_registry
 
@@ -29,6 +29,7 @@ def publish_entities(entities: Collection[Entity]):
 __all__ = (
     'Entity',
     'EntitiesEngine',
+    'db_url',
     'init_entities_engine',
     'publish_entities',
     'register_entity_plugin',

platypush/entities/_base.py

@@ -1,4 +1,5 @@
 import inspect
+import os
 import pathlib
 import types
 from datetime import datetime
@@ -18,11 +19,13 @@ from sqlalchemy import (
 )
 from sqlalchemy.orm import declarative_base, ColumnProperty
 
+from platypush.config import Config
 from platypush.message import JSONAble
 
 Base = declarative_base()
 entities_registry: Mapping[Type['Entity'], Mapping] = {}
 entity_types_registry: Dict[str, Type['Entity']] = {}
+db_url = 'sqlite:///' + os.path.join(str(Config.get('workdir') or ''), 'entities.db')
 
 
 class Entity(Base):
@@ -135,5 +138,8 @@ def init_entities_db():
     _discover_entity_types()
     db = get_plugin('db')
     assert db
-    engine = db.get_engine()
-    db.create_all(engine, Base)
+
+    engine = db.get_engine(engine=db_url)
+    with db.get_session() as session:
+        db.create_all(engine, Base)
+        session.flush()

platypush/entities/_engine.py

@@ -11,7 +11,7 @@ from sqlalchemy.orm import Session, make_transient
 from platypush.context import get_bus
 from platypush.message.event.entities import EntityUpdateEvent
 
-from ._base import Entity
+from ._base import Entity, db_url
 
 
 class EntitiesEngine(Thread):
@@ -98,7 +98,7 @@ class EntitiesEngine(Thread):
                 self._cache_entities(new_entity)
 
     def _init_entities_cache(self):
-        with self._get_db().get_session() as session:
+        with self._get_db().get_session(engine=db_url) as session:
             entities = session.query(Entity).all()
             for entity in entities:
                 make_transient(entity)
@@ -249,7 +249,7 @@ class EntitiesEngine(Thread):
         return list(new_entities.values())
 
     def _process_entities(self, *entities: Entity):
-        with self._get_db().get_session() as session:
+        with self._get_db().get_session(engine=db_url) as session:
             # Ensure that the internal IDs are set to null before the merge
             for e in entities:
                 e.id = None  # type: ignore

platypush/plugins/db/__init__.py

@@ -1,7 +1,7 @@
 import time
 from contextlib import contextmanager
 from multiprocessing import RLock
-from typing import Optional, Generator
+from typing import Optional, Generator, Union
 
 from sqlalchemy import create_engine, Table, MetaData
 from sqlalchemy.engine import Engine
@@ -39,19 +39,29 @@ class DbPlugin(Plugin):
         """
 
         super().__init__()
+        self.engine_url = engine
         self.engine = self.get_engine(engine, *args, **kwargs)
         self._session_locks = {}
 
-    def get_engine(self, engine=None, *args, **kwargs) -> Engine:
-        if engine:
+    def get_engine(
+        self, engine: Optional[Union[str, Engine]] = None, *args, **kwargs
+    ) -> Engine:
+        if engine == self.engine_url and self.engine:
+            return self.engine
+
+        if engine or not self.engine:
             if isinstance(engine, Engine):
                 return engine
-            if engine.startswith('sqlite://'):
+            if not engine:
+                engine = self.engine_url
+            if isinstance(engine, str) and engine.startswith('sqlite://'):
                 kwargs['connect_args'] = {'check_same_thread': False}
 
             return create_engine(engine, *args, **kwargs)  # type: ignore
 
-        assert self.engine
+        if not self.engine:
+            return create_engine(self.engine_url, *args, **kwargs)  # type: ignore
+
         return self.engine
 
     @staticmethod

platypush/plugins/entities/__init__.py

@@ -8,7 +8,12 @@ from sqlalchemy.orm import make_transient
 
 from platypush.config import Config
 from platypush.context import get_plugin, get_bus
-from platypush.entities import Entity, get_plugin_entity_registry, get_entities_registry
+from platypush.entities import (
+    Entity,
+    get_plugin_entity_registry,
+    get_entities_registry,
+    db_url,
+)
 from platypush.message.event.entities import EntityUpdateEvent, EntityDeleteEvent
 from platypush.plugins import Plugin, action
 
@@ -22,10 +27,10 @@ class EntitiesPlugin(Plugin):
     def __init__(self, **kwargs):
         super().__init__(**kwargs)
 
-    def _get_db(self):
+    def _get_session(self):
         db = get_plugin('db')
         assert db
-        return db
+        return db.get_session(engine=db_url)
 
     @action
     def get(
@@ -58,7 +63,6 @@ class EntitiesPlugin(Plugin):
 
             selected_types = entity_types.keys()
 
-        db = self._get_db()
         enabled_plugins = list(
             {
                 *Config.get_plugins().keys(),
@@ -66,7 +70,7 @@ class EntitiesPlugin(Plugin):
             }
         )
 
-        with db.get_session() as session:
+        with self._get_session() as session:
             query = session.query(Entity).filter(
                 or_(Entity.plugin.in_(enabled_plugins), Entity.plugin.is_(None))
             )
@@ -173,8 +177,7 @@ class EntitiesPlugin(Plugin):
         :param args: Action's extra positional arguments.
         :param kwargs: Action's extra named arguments.
         """
-        db = self._get_db()
-        with db.get_session() as session:
+        with self._get_session() as session:
             entity = session.query(Entity).filter_by(id=id).one_or_none()
 
         assert entity, f'No such entity ID: {id}'
@@ -192,7 +195,7 @@ class EntitiesPlugin(Plugin):
         :param entities: IDs of the entities to be removed.
         :return: The payload of the deleted entities.
         """
-        with self._get_db().get_session() as session:
+        with self._get_session() as session:
             entities: Collection[Entity] = (
                 session.query(Entity).filter(Entity.id.in_(entities)).all()
             )
@@ -233,7 +236,7 @@ class EntitiesPlugin(Plugin):
         :return: The updated entities.
         """
         entities = {str(k): v for k, v in entities.items()}
-        with self._get_db().get_session() as session:
+        with self._get_session() as session:
             objs = session.query(Entity).filter(Entity.id.in_(entities.keys())).all()
             for obj in objs:
                 obj.meta = {**(obj.meta or {}), **(entities.get(str(obj.id), {}))}

platypush/user/__init__.py

@@ -33,8 +33,11 @@ class UserManager:
     def __init__(self):
         self.db = get_plugin('db')
         assert self.db
-        self._engine = self.db.get_engine()
-        self.db.create_all(self._engine, Base)
+        self._engine = self.db.get_engine(engine=self.db.engine_url)
+
+        with self.db.get_session() as session:
+            self.db.create_all(self._engine, Base)
+            session.flush()
 
     @staticmethod
     def _mask_password(user):