BaseHTTPMiddleware: Exception displayed twice in logs #2715

phihung · 2024-10-02T09:35:02Z

phihung
Oct 2, 2024

Reproduction

class MyMiddleware(BaseHTTPMiddleware):
    async def dispatch(self, request: Request, call_next) -> Response:
        return await call_next(request)

def homepage(request): raise Exception("Very bad")

app = Starlette(routes=[Route("/", homepage)])
app.add_middleware(MyMiddleware)  # No more problem if we remove this line

Exception is shown twice in the logs

ERROR:    Exception in ASGI application
  + Exception Group Traceback (most recent call last):
     ...
  |   File ".venv/lib/python3.10/site-packages/anyio/_backends/_asyncio.py", line 736, in __aexit__
  |     raise BaseExceptionGroup(
  | exceptiongroup.ExceptionGroup: unhandled errors in a TaskGroup (1 sub-exception)
  +-+---------------- 1 ----------------
    | Traceback (most recent call last):
          ...
    |   File "a.py", line 15, in homepage
    |     raise Exception("Very bad")
    | Exception: Very bad
    +------------------------------------

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  ...
  File "a.py", line 15, in homepage
    raise Exception("Very bad")
Exception: Very bad

Full stack trace

ERROR:    Exception in ASGI application
  + Exception Group Traceback (most recent call last):
  |   File ".venv/lib/python3.10/site-packages/starlette/_utils.py", line 77, in collapse_excgroups
  |     yield
  |   File ".venv/lib/python3.10/site-packages/starlette/middleware/base.py", line 186, in __call__
  |     async with anyio.create_task_group() as task_group:
  |   File ".venv/lib/python3.10/site-packages/anyio/_backends/_asyncio.py", line 736, in __aexit__
  |     raise BaseExceptionGroup(
  | exceptiongroup.ExceptionGroup: unhandled errors in a TaskGroup (1 sub-exception)
  +-+---------------- 1 ----------------
    | Traceback (most recent call last):
    |   File ".venv/lib/python3.10/site-packages/uvicorn/protocols/http/httptools_impl.py", line 401, in run_asgi
    |     result = await app(  # type: ignore[func-returns-value]
    |   File ".venv/lib/python3.10/site-packages/uvicorn/middleware/proxy_headers.py", line 60, in __call__
    |     return await self.app(scope, receive, send)
    |   File ".venv/lib/python3.10/site-packages/starlette/applications.py", line 113, in __call__
    |     await self.middleware_stack(scope, receive, send)
    |   File ".venv/lib/python3.10/site-packages/starlette/middleware/errors.py", line 187, in __call__
    |     raise exc
    |   File ".venv/lib/python3.10/site-packages/starlette/middleware/errors.py", line 165, in __call__
    |     await self.app(scope, receive, _send)
    |   File ".venv/lib/python3.10/site-packages/starlette/middleware/base.py", line 185, in __call__
    |     with collapse_excgroups():
    |   File "...uv/python/cpython-3.10.0-macos-aarch64-none/lib/python3.10/contextlib.py", line 153, in __exit__
    |     self.gen.throw(typ, value, traceback)
    |   File ".venv/lib/python3.10/site-packages/starlette/_utils.py", line 83, in collapse_excgroups
    |     raise exc
    |   File ".venv/lib/python3.10/site-packages/starlette/middleware/base.py", line 187, in __call__
    |     response = await self.dispatch_func(request, call_next)
    |   File "a.py", line 11, in dispatch
    |     return await call_next(request)
    |   File ".venv/lib/python3.10/site-packages/starlette/middleware/base.py", line 163, in call_next
    |     raise app_exc
    |   File ".venv/lib/python3.10/site-packages/starlette/middleware/base.py", line 149, in coro
    |     await self.app(scope, receive_or_disconnect, send_no_error)
    |   File ".venv/lib/python3.10/site-packages/starlette/middleware/exceptions.py", line 62, in __call__
    |     await wrap_app_handling_exceptions(self.app, conn)(scope, receive, send)
    |   File ".venv/lib/python3.10/site-packages/starlette/_exception_handler.py", line 62, in wrapped_app
    |     raise exc
    |   File ".venv/lib/python3.10/site-packages/starlette/_exception_handler.py", line 51, in wrapped_app
    |     await app(scope, receive, sender)
    |   File ".venv/lib/python3.10/site-packages/starlette/routing.py", line 715, in __call__
    |     await self.middleware_stack(scope, receive, send)
    |   File ".venv/lib/python3.10/site-packages/starlette/routing.py", line 735, in app
    |     await route.handle(scope, receive, send)
    |   File ".venv/lib/python3.10/site-packages/starlette/routing.py", line 288, in handle
    |     await self.app(scope, receive, send)
    |   File ".venv/lib/python3.10/site-packages/starlette/routing.py", line 76, in app
    |     await wrap_app_handling_exceptions(app, request)(scope, receive, send)
    |   File ".venv/lib/python3.10/site-packages/starlette/_exception_handler.py", line 62, in wrapped_app
    |     raise exc
    |   File ".venv/lib/python3.10/site-packages/starlette/_exception_handler.py", line 51, in wrapped_app
    |     await app(scope, receive, sender)
    |   File ".venv/lib/python3.10/site-packages/starlette/routing.py", line 73, in app
    |     response = await f(request)
    |   File ".venv/lib/python3.10/site-packages/starlette/concurrency.py", line 39, in run_in_threadpool
    |     return await anyio.to_thread.run_sync(func, *args)
    |   File ".venv/lib/python3.10/site-packages/anyio/to_thread.py", line 56, in run_sync
    |     return await get_async_backend().run_sync_in_worker_thread(
    |   File ".venv/lib/python3.10/site-packages/anyio/_backends/_asyncio.py", line 2405, in run_sync_in_worker_thread
    |     return await future
    |   File ".venv/lib/python3.10/site-packages/anyio/_backends/_asyncio.py", line 914, in run
    |     result = context.run(func, *args)
    |   File "a.py", line 15, in homepage
    |     raise Exception("Very bad")
    | Exception: Very bad
    +------------------------------------

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File ".venv/lib/python3.10/site-packages/uvicorn/protocols/http/httptools_impl.py", line 401, in run_asgi
    result = await app(  # type: ignore[func-returns-value]
  File ".venv/lib/python3.10/site-packages/uvicorn/middleware/proxy_headers.py", line 60, in __call__
    return await self.app(scope, receive, send)
  File ".venv/lib/python3.10/site-packages/starlette/applications.py", line 113, in __call__
    await self.middleware_stack(scope, receive, send)
  File ".venv/lib/python3.10/site-packages/starlette/middleware/errors.py", line 187, in __call__
    raise exc
  File ".venv/lib/python3.10/site-packages/starlette/middleware/errors.py", line 165, in __call__
    await self.app(scope, receive, _send)
  File ".venv/lib/python3.10/site-packages/starlette/middleware/base.py", line 185, in __call__
    with collapse_excgroups():
  File ".../uv/python/cpython-3.10.0-macos-aarch64-none/lib/python3.10/contextlib.py", line 153, in __exit__
    self.gen.throw(typ, value, traceback)
  File ".venv/lib/python3.10/site-packages/starlette/_utils.py", line 83, in collapse_excgroups
    raise exc
  File ".venv/lib/python3.10/site-packages/starlette/middleware/base.py", line 187, in __call__
    response = await self.dispatch_func(request, call_next)
  File "a.py", line 11, in dispatch
    return await call_next(request)
  File ".venv/lib/python3.10/site-packages/starlette/middleware/base.py", line 163, in call_next
    raise app_exc
  File ".venv/lib/python3.10/site-packages/starlette/middleware/base.py", line 149, in coro
    await self.app(scope, receive_or_disconnect, send_no_error)
  File ".venv/lib/python3.10/site-packages/starlette/middleware/exceptions.py", line 62, in __call__
    await wrap_app_handling_exceptions(self.app, conn)(scope, receive, send)
  File ".venv/lib/python3.10/site-packages/starlette/_exception_handler.py", line 62, in wrapped_app
    raise exc
  File ".venv/lib/python3.10/site-packages/starlette/_exception_handler.py", line 51, in wrapped_app
    await app(scope, receive, sender)
  File ".venv/lib/python3.10/site-packages/starlette/routing.py", line 715, in __call__
    await self.middleware_stack(scope, receive, send)
  File ".venv/lib/python3.10/site-packages/starlette/routing.py", line 735, in app
    await route.handle(scope, receive, send)
  File ".venv/lib/python3.10/site-packages/starlette/routing.py", line 288, in handle
    await self.app(scope, receive, send)
  File ".venv/lib/python3.10/site-packages/starlette/routing.py", line 76, in app
    await wrap_app_handling_exceptions(app, request)(scope, receive, send)
  File ".venv/lib/python3.10/site-packages/starlette/_exception_handler.py", line 62, in wrapped_app
    raise exc
  File ".venv/lib/python3.10/site-packages/starlette/_exception_handler.py", line 51, in wrapped_app
    await app(scope, receive, sender)
  File ".venv/lib/python3.10/site-packages/starlette/routing.py", line 73, in app
    response = await f(request)
  File ".venv/lib/python3.10/site-packages/starlette/concurrency.py", line 39, in run_in_threadpool
    return await anyio.to_thread.run_sync(func, *args)
  File ".venv/lib/python3.10/site-packages/anyio/to_thread.py", line 56, in run_sync
    return await get_async_backend().run_sync_in_worker_thread(
  File ".venv/lib/python3.10/site-packages/anyio/_backends/_asyncio.py", line 2405, in run_sync_in_worker_thread
    return await future
  File ".venv/lib/python3.10/site-packages/anyio/_backends/_asyncio.py", line 914, in run
    result = context.run(func, *args)
  File "a.py", line 15, in homepage
    raise Exception("Very bad")
Exception: Very bad

Answered by Kludex

Nov 3, 2025

This is solved.

View full answer

Kludex · 2024-10-02T12:26:25Z

Kludex
Oct 2, 2024
Maintainer

What's your Starlette version?

0 replies

phihung · 2024-10-02T13:08:58Z

phihung
Oct 2, 2024
Author

Starlette 0.38.6
Uvicorn 0.31.0
Python 3.10.0

2 replies

Kludex Oct 2, 2024
Maintainer

Does it reproduce in the last Starlette?

phihung Oct 2, 2024
Author

Yes. Same problem with

Starlette 0.39.2, python 3.11.10, Mac osx
Starlette main commit e116840

phihung · 2024-10-23T15:28:54Z

phihung
Oct 23, 2024
Author

Hi. Do you think I should create an issue for this?
It is just in the logs, so nothing urgent.

0 replies

Kludex · 2025-11-03T07:58:32Z

Kludex
Nov 3, 2025
Maintainer

This is solved.

0 replies

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