Document task DB access and unify background task DB handling

backend/app/tasks/blocklist_import.py

@@ -17,12 +17,11 @@ from typing import TYPE_CHECKING, Any
 
 import structlog
 
-from app.db import open_db
 from app.services import ban_service, blocklist_service
+from app.tasks.db import task_db
 from app.utils.runtime_state import get_effective_settings
 
 if TYPE_CHECKING:
-    import aiosqlite
     from aiohttp import ClientSession
     from fastapi import FastAPI
 
@@ -34,11 +33,6 @@ log: structlog.stdlib.BoundLogger = structlog.get_logger()
 JOB_ID: str = "blocklist_import"
 
 
-async def _get_db(settings: Settings) -> tuple[aiosqlite.Connection, bool]:
-    db = await open_db(settings.database_path)
-    return db, True
-
-
 async def _run_import_with_resources(settings: Settings, http_session: ClientSession) -> None:
     """APScheduler callback that imports all enabled blocklist sources.
 
@@ -46,17 +40,17 @@ async def _run_import_with_resources(settings: Settings, http_session: ClientSes
         settings: The resolved application settings used for database access.
         http_session: The shared aiohttp session used for blocklist downloads.
     """
-    db, close_db = await _get_db(settings)
     socket_path: str = settings.fail2ban_socket
 
     log.info("blocklist_import_starting")
     try:
-        result = await blocklist_service.import_all(
-            db,
-            http_session,
-            socket_path,
-            ban_ip=ban_service.ban_ip,
-        )
+        async with task_db(settings) as db:
+            result = await blocklist_service.import_all(
+                db,
+                http_session,
+                socket_path,
+                ban_ip=ban_service.ban_ip,
+            )
         log.info(
             "blocklist_import_finished",
             total_imported=result.total_imported,
@@ -65,9 +59,6 @@ async def _run_import_with_resources(settings: Settings, http_session: ClientSes
         )
     except Exception:
         log.exception("blocklist_import_unexpected_error")
-    finally:
-        if close_db:
-            await db.close()
 
 
 run_import_with_resources = _run_import_with_resources
@@ -91,12 +82,8 @@ async def register(app: FastAPI) -> None:
             ``app.state.scheduler`` will receive the job.
     """
     settings = get_effective_settings(app)
-    db, close_db = await _get_db(settings)
-    try:
+    async with task_db(settings) as db:
         config = await blocklist_service.get_schedule(db)
-    finally:
-        if close_db:
-            await db.close()
 
     _apply_schedule(app, config)
 
@@ -114,12 +101,8 @@ def reschedule(app: FastAPI) -> None:
 
     async def _do_reschedule() -> None:
         settings = get_effective_settings(app)
-        db, close_db = await _get_db(settings)
-        try:
+        async with task_db(settings) as db:
             config = await blocklist_service.get_schedule(db)
-        finally:
-            if close_db:
-                await db.close()
         _apply_schedule(app, config)
 
     asyncio.ensure_future(_do_reschedule())