🗃️ Use of dedicated db sessions

backend/backend/db/db.py

@@ -1,5 +1,10 @@
+from logging import getLogger
+from typing import Annotated, AsyncIterator
+
+from fastapi import Depends
 from opentelemetry.instrumentation.sqlalchemy import SQLAlchemyInstrumentor
 from sqlalchemy import text
+from sqlalchemy.exc import SQLAlchemyError
 from sqlalchemy.ext.asyncio import (
     async_sessionmaker,
     AsyncEngine,
@@ -10,42 +15,47 @@ from sqlalchemy.ext.asyncio import (
 from .base_class import Base
 
 
+logger = getLogger(__name__)
+
+
 class Database:
     def __init__(self) -> None:
-        self._engine: AsyncEngine | None = None
-        self._session_maker: async_sessionmaker[AsyncSession] | None = None
-        self._session: AsyncSession | None = None
+        self._async_engine: AsyncEngine | None = None
+        self._async_session_local: async_sessionmaker[AsyncSession] | None = None
 
-    @property
-    def session(self) -> AsyncSession | None:
-        if self._session is None and (session_maker := self._session_maker) is not None:
-            self._session = session_maker()
-        return self._session
+    async def get_session(self) -> AsyncSession | None:
+        try:
+            return self._async_session_local()  # type: ignore
 
+        except (SQLAlchemyError, AttributeError) as e:
+            logger.exception(e)
+
+        return None
+
+    # TODO: Preserve UserLastStopSearchResults table from drop.
     async def connect(self, db_path: str, clear_static_data: bool = False) -> bool:
+        self._async_engine = create_async_engine(
+            db_path, pool_pre_ping=True, pool_size=10, max_overflow=20
+        )
 
-        # TODO: Preserve UserLastStopSearchResults table from drop.
-        self._engine = create_async_engine(db_path)
-        if self._engine is not None:
-            SQLAlchemyInstrumentor().instrument(engine=self._engine.sync_engine)
+        if self._async_engine is not None:
+            SQLAlchemyInstrumentor().instrument(engine=self._async_engine.sync_engine)
 
-            self._session_maker = async_sessionmaker(
-                self._engine, expire_on_commit=False, class_=AsyncSession
+            self._async_session_local = async_sessionmaker(
+                bind=self._async_engine,
+                # autoflush=False,
+                expire_on_commit=False,
+                class_=AsyncSession,
             )
-            if (session := self.session) is not None:
-                await session.execute(text("CREATE EXTENSION IF NOT EXISTS pg_trgm;"))
 
-            async with self._engine.begin() as conn:
+            async with self._async_engine.begin() as session:
+                await session.execute(text("CREATE EXTENSION IF NOT EXISTS pg_trgm;"))
                 if clear_static_data:
-                    await conn.run_sync(Base.metadata.drop_all)
-                await conn.run_sync(Base.metadata.create_all)
+                    await session.run_sync(Base.metadata.drop_all)
+                    await session.run_sync(Base.metadata.create_all)
 
         return True
 
     async def disconnect(self) -> None:
-        if self._session is not None:
-            await self._session.close()
-            self._session = None
-
-        if self._engine is not None:
-            await self._engine.dispose()
+        if self._async_engine is not None:
+            await self._async_engine.dispose()