Refactor backend to use request-scoped SQLite connections

backend/app/tasks/blocklist_import.py

@@ -17,9 +17,13 @@ from typing import TYPE_CHECKING, Any
 
 import structlog
 
+from app.db import open_db
 from app.models.blocklist import ScheduleFrequency
 from app.services import blocklist_service
 
+if TYPE_CHECKING:
+    import aiosqlite
+
 if TYPE_CHECKING:
     from fastapi import FastAPI
 
@@ -29,6 +33,15 @@ log: structlog.stdlib.BoundLogger = structlog.get_logger()
 JOB_ID: str = "blocklist_import"
 
 
+async def _get_db(app: Any) -> tuple[aiosqlite.Connection, bool]:
+    existing_db = getattr(app.state, "db", None)
+    if existing_db is not None:
+        return existing_db, False
+
+    db = await open_db(app.state.settings.database_path)
+    return db, True
+
+
 async def _run_import(app: Any) -> None:
     """APScheduler callback that imports all enabled blocklist sources.
 
@@ -39,12 +52,10 @@ async def _run_import(app: Any) -> None:
         app: The :class:`fastapi.FastAPI` application instance passed via
             APScheduler ``kwargs``.
     """
-    db = app.state.db
+    db, close_db = await _get_db(app)
     http_session = app.state.http_session
     socket_path: str = app.state.settings.fail2ban_socket
 
-    from app.services import jail_service
-
     log.info("blocklist_import_starting")
     try:
         result = await blocklist_service.import_all(
@@ -60,6 +71,9 @@ async def _run_import(app: Any) -> None:
         )
     except Exception:
         log.exception("blocklist_import_unexpected_error")
+    finally:
+        if close_db:
+            await db.close()
 
 
 def register(app: FastAPI) -> None:
@@ -78,7 +92,12 @@ def register(app: FastAPI) -> None:
     import asyncio  # noqa: PLC0415
 
     async def _do_register() -> None:
-        config = await blocklist_service.get_schedule(app.state.db)
+        db, close_db = await _get_db(app)
+        try:
+            config = await blocklist_service.get_schedule(db)
+        finally:
+            if close_db:
+                await db.close()
         _apply_schedule(app, config)
 
     # APScheduler is synchronous at registration time; use asyncio to read
@@ -104,7 +123,12 @@ def reschedule(app: FastAPI) -> None:
     import asyncio  # noqa: PLC0415
 
     async def _do_reschedule() -> None:
-        config = await blocklist_service.get_schedule(app.state.db)
+        db, close_db = await _get_db(app)
+        try:
+            config = await blocklist_service.get_schedule(db)
+        finally:
+            if close_db:
+                await db.close()
         _apply_schedule(app, config)
 
     asyncio.ensure_future(_do_reschedule())