From cdf66eeff50ccce349df4bbbf91d2a2e292430db Mon Sep 17 00:00:00 2001 From: Jean Hominal Date: Sat, 24 Sep 2022 07:29:08 +0200 Subject: [PATCH] Replace task cancellation in `BaseHTTPMiddleware` with `http.disconnect`+`recv_stream.close` (#1715) * replace BaseMiddleware cancellation after request send with closing recv_stream + http.disconnect in receive fixes #1438 * Add no cover pragma on pytest.fail in tests/middleware/test_base.py Co-authored-by: Adrian Garcia Badaracco <1755071+adriangb@users.noreply.github.com> * make http_disconnect_while_sending test more robust in the face of scheduling issues * Fix issue with running middleware context manager Reported in https://github.com/encode/starlette/issues/1678#issuecomment-1172916042 Co-authored-by: Adrian Garcia Badaracco <1755071+adriangb@users.noreply.github.com> Co-authored-by: Marcelo Trylesinski --- starlette/middleware/base.py | 40 ++++++- tests/middleware/test_base.py | 207 ++++++++++++++++++++++++++++++++++ 2 files changed, 244 insertions(+), 3 deletions(-) diff --git a/starlette/middleware/base.py b/starlette/middleware/base.py index 49a5e3e2d7..586c9870dc 100644 --- a/starlette/middleware/base.py +++ b/starlette/middleware/base.py @@ -4,12 +4,13 @@ from starlette.requests import Request from starlette.responses import Response, StreamingResponse -from starlette.types import ASGIApp, Receive, Scope, Send +from starlette.types import ASGIApp, Message, Receive, Scope, Send RequestResponseEndpoint = typing.Callable[[Request], typing.Awaitable[Response]] DispatchFunction = typing.Callable[ [Request, RequestResponseEndpoint], typing.Awaitable[Response] ] +T = typing.TypeVar("T") class BaseHTTPMiddleware: @@ -24,19 +25,52 @@ async def __call__(self, scope: Scope, receive: Receive, send: Send) -> None: await self.app(scope, receive, send) return + response_sent = anyio.Event() + async def call_next(request: Request) -> Response: app_exc: typing.Optional[Exception] = None send_stream, recv_stream = anyio.create_memory_object_stream() + async def receive_or_disconnect() -> Message: + if response_sent.is_set(): + return {"type": "http.disconnect"} + + async with anyio.create_task_group() as task_group: + + async def wrap(func: typing.Callable[[], typing.Awaitable[T]]) -> T: + result = await func() + task_group.cancel_scope.cancel() + return result + + task_group.start_soon(wrap, response_sent.wait) + message = await wrap(request.receive) + + if response_sent.is_set(): + return {"type": "http.disconnect"} + + return message + + async def close_recv_stream_on_response_sent() -> None: + await response_sent.wait() + recv_stream.close() + + async def send_no_error(message: Message) -> None: + try: + await send_stream.send(message) + except anyio.BrokenResourceError: + # recv_stream has been closed, i.e. response_sent has been set. + return + async def coro() -> None: nonlocal app_exc async with send_stream: try: - await self.app(scope, request.receive, send_stream.send) + await self.app(scope, receive_or_disconnect, send_no_error) except Exception as exc: app_exc = exc + task_group.start_soon(close_recv_stream_on_response_sent) task_group.start_soon(coro) try: @@ -71,7 +105,7 @@ async def body_stream() -> typing.AsyncGenerator[bytes, None]: request = Request(scope, receive=receive) response = await self.dispatch_func(request, call_next) await response(scope, receive, send) - task_group.cancel_scope.cancel() + response_sent.set() async def dispatch( self, request: Request, call_next: RequestResponseEndpoint diff --git a/tests/middleware/test_base.py b/tests/middleware/test_base.py index 976d77b860..ed0734bd38 100644 --- a/tests/middleware/test_base.py +++ b/tests/middleware/test_base.py @@ -1,8 +1,11 @@ import contextvars +from contextlib import AsyncExitStack +import anyio import pytest from starlette.applications import Starlette +from starlette.background import BackgroundTask from starlette.middleware import Middleware from starlette.middleware.base import BaseHTTPMiddleware from starlette.responses import PlainTextResponse, StreamingResponse @@ -206,3 +209,207 @@ async def homepage(request): client = test_client_factory(app) response = client.get("/") assert response.status_code == 200, response.content + + +@pytest.mark.anyio +async def test_run_background_tasks_even_if_client_disconnects(): + # test for https://github.com/encode/starlette/issues/1438 + request_body_sent = False + response_complete = anyio.Event() + background_task_run = anyio.Event() + + async def sleep_and_set(): + # small delay to give BaseHTTPMiddleware a chance to cancel us + # this is required to make the test fail prior to fixing the issue + # so do not be surprised if you remove it and the test still passes + await anyio.sleep(0.1) + background_task_run.set() + + async def endpoint_with_background_task(_): + return PlainTextResponse(background=BackgroundTask(sleep_and_set)) + + async def passthrough(request, call_next): + return await call_next(request) + + app = Starlette( + middleware=[Middleware(BaseHTTPMiddleware, dispatch=passthrough)], + routes=[Route("/", endpoint_with_background_task)], + ) + + scope = { + "type": "http", + "version": "3", + "method": "GET", + "path": "/", + } + + async def receive(): + nonlocal request_body_sent + if not request_body_sent: + request_body_sent = True + return {"type": "http.request", "body": b"", "more_body": False} + # We simulate a client that disconnects immediately after receiving the response + await response_complete.wait() + return {"type": "http.disconnect"} + + async def send(message): + if message["type"] == "http.response.body": + if not message.get("more_body", False): + response_complete.set() + + await app(scope, receive, send) + + assert background_task_run.is_set() + + +@pytest.mark.anyio +async def test_run_context_manager_exit_even_if_client_disconnects(): + # test for https://github.com/encode/starlette/issues/1678#issuecomment-1172916042 + request_body_sent = False + response_complete = anyio.Event() + context_manager_exited = anyio.Event() + + async def sleep_and_set(): + # small delay to give BaseHTTPMiddleware a chance to cancel us + # this is required to make the test fail prior to fixing the issue + # so do not be surprised if you remove it and the test still passes + await anyio.sleep(0.1) + context_manager_exited.set() + + class ContextManagerMiddleware: + def __init__(self, app): + self.app = app + + async def __call__(self, scope: Scope, receive: Receive, send: Send): + async with AsyncExitStack() as stack: + stack.push_async_callback(sleep_and_set) + await self.app(scope, receive, send) + + async def simple_endpoint(_): + return PlainTextResponse(background=BackgroundTask(sleep_and_set)) + + async def passthrough(request, call_next): + return await call_next(request) + + app = Starlette( + middleware=[ + Middleware(BaseHTTPMiddleware, dispatch=passthrough), + Middleware(ContextManagerMiddleware), + ], + routes=[Route("/", simple_endpoint)], + ) + + scope = { + "type": "http", + "version": "3", + "method": "GET", + "path": "/", + } + + async def receive(): + nonlocal request_body_sent + if not request_body_sent: + request_body_sent = True + return {"type": "http.request", "body": b"", "more_body": False} + # We simulate a client that disconnects immediately after receiving the response + await response_complete.wait() + return {"type": "http.disconnect"} + + async def send(message): + if message["type"] == "http.response.body": + if not message.get("more_body", False): + response_complete.set() + + await app(scope, receive, send) + + assert context_manager_exited.is_set() + + +def test_app_receives_http_disconnect_while_sending_if_discarded(test_client_factory): + class DiscardingMiddleware(BaseHTTPMiddleware): + async def dispatch(self, request, call_next): + await call_next(request) + return PlainTextResponse("Custom") + + async def downstream_app(scope, receive, send): + await send( + { + "type": "http.response.start", + "status": 200, + "headers": [ + (b"content-type", b"text/plain"), + ], + } + ) + async with anyio.create_task_group() as task_group: + + async def cancel_on_disconnect(): + while True: + message = await receive() + if message["type"] == "http.disconnect": + task_group.cancel_scope.cancel() + break + + task_group.start_soon(cancel_on_disconnect) + + # A timeout is set for 0.1 second in order to ensure that + # cancel_on_disconnect is scheduled by the event loop + with anyio.move_on_after(0.1): + while True: + await send( + { + "type": "http.response.body", + "body": b"chunk ", + "more_body": True, + } + ) + + pytest.fail( + "http.disconnect should have been received and canceled the scope" + ) # pragma: no cover + + app = DiscardingMiddleware(downstream_app) + + client = test_client_factory(app) + response = client.get("/does_not_exist") + assert response.text == "Custom" + + +def test_app_receives_http_disconnect_after_sending_if_discarded(test_client_factory): + class DiscardingMiddleware(BaseHTTPMiddleware): + async def dispatch(self, request, call_next): + await call_next(request) + return PlainTextResponse("Custom") + + async def downstream_app(scope, receive, send): + await send( + { + "type": "http.response.start", + "status": 200, + "headers": [ + (b"content-type", b"text/plain"), + ], + } + ) + await send( + { + "type": "http.response.body", + "body": b"first chunk, ", + "more_body": True, + } + ) + await send( + { + "type": "http.response.body", + "body": b"second chunk", + "more_body": True, + } + ) + message = await receive() + assert message["type"] == "http.disconnect" + + app = DiscardingMiddleware(downstream_app) + + client = test_client_factory(app) + response = client.get("/does_not_exist") + assert response.text == "Custom"