Remove global from FastAPI app.py (#59772) (#62997)

* Remove global from FastAPI app.py

* Remove global from FastAPI app.py

Co-authored-by: Jens Scheffler <95105677+jscheffl@users.noreply.github.com>

Author: 2 people

airflow-core/src/airflow/api_fastapi/app.py

@@ -18,6 +18,7 @@
 
 import logging
 from contextlib import AsyncExitStack, asynccontextmanager
+from functools import cache
 from typing import TYPE_CHECKING, cast
 from urllib.parse import urlsplit
 
@@ -64,8 +65,9 @@ def get_cookie_path() -> str:
 
 log = logging.getLogger(__name__)
 
-app: FastAPI | None = None
-auth_manager: BaseAuthManager | None = None
+
+class _AuthManagerState:
+    instance: BaseAuthManager | None = None
 
 
 @asynccontextmanager
@@ -117,19 +119,16 @@ def create_app(apps: str = "all") -> FastAPI:
     return app
 
 
+@cache
 def cached_app(config=None, testing=False, apps="all") -> FastAPI:
     """Return cached instance of Airflow API app."""
-    global app
-    if not app:
-        app = create_app(apps=apps)
-    return app
+    return create_app(apps=apps)
 
 
 def purge_cached_app() -> None:
     """Remove the cached version of the app and auth_manager in global state."""
-    global app, auth_manager
-    app = None
-    auth_manager = None
+    cached_app.cache_clear()
+    _AuthManagerState.instance = None
 
 
 def get_auth_manager_cls() -> type[BaseAuthManager]:
@@ -150,10 +149,9 @@ def get_auth_manager_cls() -> type[BaseAuthManager]:
 
 def create_auth_manager() -> BaseAuthManager:
     """Create the auth manager."""
-    global auth_manager
     auth_manager_cls = get_auth_manager_cls()
-    auth_manager = auth_manager_cls()
-    return auth_manager
+    _AuthManagerState.instance = auth_manager_cls()
+    return _AuthManagerState.instance
 
 
 def init_auth_manager(app: FastAPI | None = None) -> BaseAuthManager:
@@ -171,12 +169,12 @@ def init_auth_manager(app: FastAPI | None = None) -> BaseAuthManager:
 
 def get_auth_manager() -> BaseAuthManager:
     """Return the auth manager, provided it's been initialized before."""
-    if auth_manager is None:
+    if _AuthManagerState.instance is None:
         raise RuntimeError(
             "Auth Manager has not been initialized yet. "
             "The `init_auth_manager` method needs to be called first."
         )
-    return auth_manager
+    return _AuthManagerState.instance
 
 
 def init_plugins(app: FastAPI) -> None: