Cache entry has expired

[giosava94]

Hi,
I am using flaat in a FastAPI application. The application is a long running server exposing a set of REST API.

There is a client which periocally concacts the application. It provides an access_token and it has a refresh token with a long expiration time.

Unfortunately, after 1 month (more or less) I periodically have this problem. When this happens the client can't perform any operation on the server and the solution is usually to restart the application. Instead other clients can query the server.

I can't understand what is causing this and how can I eventually configure/clear the cache.

Here the output:

[2025-06-23 05:48:23 +0000] [7] [ERROR] Exception in ASGI application
Traceback (most recent call last):
  File "/usr/local/lib/python3.11/site-packages/uvicorn/protocols/http/httptools_impl.py", line 409, in run_asgi
    result = await app(  # type: ignore[func-returns-value]
             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/local/lib/python3.11/site-packages/uvicorn/middleware/proxy_headers.py", line 60, in __call__
    return await self.app(scope, receive, send)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/root/.local/lib/python3.11/site-packages/fastapi/applications.py", line 1054, in __call__
    await super().__call__(scope, receive, send)
  File "/root/.local/lib/python3.11/site-packages/starlette/applications.py", line 116, in __call__
    await self.middleware_stack(scope, receive, send)
  File "/root/.local/lib/python3.11/site-packages/starlette/middleware/errors.py", line 186, in __call__
    raise exc
  File "/root/.local/lib/python3.11/site-packages/starlette/middleware/errors.py", line 164, in __call__
    await self.app(scope, receive, _send)
  File "/root/.local/lib/python3.11/site-packages/starlette/middleware/exceptions.py", line 62, in __call__
    await wrap_app_handling_exceptions(self.app, conn)(scope, receive, send)
  File "/root/.local/lib/python3.11/site-packages/starlette/_exception_handler.py", line 55, in wrapped_app
    raise exc
  File "/root/.local/lib/python3.11/site-packages/starlette/_exception_handler.py", line 44, in wrapped_app
    await app(scope, receive, sender)
  File "/root/.local/lib/python3.11/site-packages/starlette/routing.py", line 746, in __call__
    await route.handle(scope, receive, send)
  File "/root/.local/lib/python3.11/site-packages/starlette/routing.py", line 459, in handle
    await self.app(scope, receive, send)
  File "/root/.local/lib/python3.11/site-packages/fastapi/applications.py", line 1054, in __call__
    await super().__call__(scope, receive, send)
  File "/root/.local/lib/python3.11/site-packages/starlette/applications.py", line 116, in __call__
    await self.middleware_stack(scope, receive, send)
  File "/root/.local/lib/python3.11/site-packages/starlette/middleware/errors.py", line 186, in __call__
    raise exc
  File "/root/.local/lib/python3.11/site-packages/starlette/middleware/errors.py", line 164, in __call__
    await self.app(scope, receive, _send)
  File "/root/.local/lib/python3.11/site-packages/starlette/middleware/exceptions.py", line 62, in __call__
    await wrap_app_handling_exceptions(self.app, conn)(scope, receive, send)
  File "/root/.local/lib/python3.11/site-packages/starlette/_exception_handler.py", line 55, in wrapped_app
    raise exc
  File "/root/.local/lib/python3.11/site-packages/starlette/_exception_handler.py", line 44, in wrapped_app
    await app(scope, receive, sender)
  File "/root/.local/lib/python3.11/site-packages/starlette/routing.py", line 746, in __call__
    await route.handle(scope, receive, send)
  File "/root/.local/lib/python3.11/site-packages/starlette/routing.py", line 288, in handle
    await self.app(scope, receive, send)
  File "/root/.local/lib/python3.11/site-packages/starlette/routing.py", line 75, in app
    await wrap_app_handling_exceptions(app, request)(scope, receive, send)
  File "/root/.local/lib/python3.11/site-packages/starlette/_exception_handler.py", line 55, in wrapped_app
    raise exc
  File "/root/.local/lib/python3.11/site-packages/starlette/_exception_handler.py", line 44, in wrapped_app
    await app(scope, receive, sender)
  File "/root/.local/lib/python3.11/site-packages/starlette/routing.py", line 70, in app
    response = await func(request)
               ^^^^^^^^^^^^^^^^^^^
  File "/root/.local/lib/python3.11/site-packages/fastapi/routing.py", line 285, in app
    raise e
  File "/root/.local/lib/python3.11/site-packages/fastapi/routing.py", line 275, in app
    solved_result = await solve_dependencies(
                    ^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/root/.local/lib/python3.11/site-packages/fastapi/dependencies/utils.py", line 600, in solve_dependencies
    solved = await run_in_threadpool(call, **sub_values)
             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/root/.local/lib/python3.11/site-packages/starlette/concurrency.py", line 35, in run_in_threadpool
    return await anyio.to_thread.run_sync(func, *args)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/root/.local/lib/python3.11/site-packages/anyio/to_thread.py", line 56, in run_sync
    return await get_async_backend().run_sync_in_worker_thread(
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/root/.local/lib/python3.11/site-packages/anyio/_backends/_asyncio.py", line 2177, in run_sync_in_worker_thread
    return await future
           ^^^^^^^^^^^^
  File "/root/.local/lib/python3.11/site-packages/anyio/_backends/_asyncio.py", line 859, in run
    result = context.run(func, *args)
             ^^^^^^^^^^^^^^^^^^^^^^^^
  File "/app/my_app/auth.py", line 62, in strict_security
    user_infos = flaat.get_user_infos_from_request(request)
                 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/root/.local/lib/python3.11/site-packages/flaat/__init__.py", line 234, in get_user_infos_from_request
    user_infos = self.get_user_infos_from_access_token(access_token)
                 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/root/.local/lib/python3.11/site-packages/cachetools/__init__.py", line 739, in wrapper
    cache[k] = v
    ~~~~~^^^
  File "/root/.local/lib/python3.11/site-packages/cachetools/__init__.py", line 217, in __setitem__
    cache_setitem(self, key, value)
  File "/root/.local/lib/python3.11/site-packages/cachetools/__init__.py", line 79, in __setitem__
    self.popitem()
  File "/root/.local/lib/python3.11/site-packages/cachetools/__init__.py", line 231, in popitem
    return (key, self.pop(key))
                 ^^^^^^^^^^^^^
  File "/root/.local/lib/python3.11/site-packages/cachetools/__init__.py", line 113, in pop
    value = self[key]
            ~~~~^^^^^
  File "/root/.local/lib/python3.11/site-packages/flaat/caches.py", line 20, in __getitem__
    _fail("Cache entry has expired")
  File "/root/.local/lib/python3.11/site-packages/flaat/caches.py", line 13, in _fail
    raise KeyError(msg)
KeyError: 'Cache entry has expired'

[marcvs]

Phew. I took a look at the code I've written quite some time ago...
I do store the lifetime of the AccessToken in the cache (using first the exp field of the introspection response, if available. If not available, I try exp field of the json AT).
If that value is smaller than what time.time() returns, I return: 'Cache entry has expired'.

It looks very much like the AT is actually expired.
I agree that a keyError and the message itself are misleading.
I'd change the error handling, if you can confirm, that the AT is actually expired (1 month is actually pretty long for an AT).

If you can verify that the AT is not expired.... well, then we'll have to find ways on how we can debug this.