Fix system routes polluting the middleware cache

Author: bdraco

CHANGES/9852.bugfix.rst

@@ -0,0 +1 @@
+Fixed system routes polluting the middleware cache -- by :user:`bdraco`.

aiohttp/web_app.py

@@ -1,7 +1,7 @@
 import asyncio
 import logging
 import warnings
-from functools import cache, partial, update_wrapper
+from functools import lru_cache, partial, update_wrapper
 from typing import (
     TYPE_CHECKING,
     Any,
@@ -44,6 +44,7 @@
     MaskDomain,
     MatchedSubAppResource,
     PrefixedSubAppResource,
+    SystemRoute,
     UrlDispatcher,
 )
 
@@ -70,7 +71,6 @@
 _Resource = TypeVar("_Resource", bound=AbstractResource)
 
 
-@cache
 def _build_middlewares(
     handler: Handler, apps: Tuple["Application", ...]
 ) -> Callable[[Request], Awaitable[StreamResponse]]:
@@ -84,6 +84,9 @@ def _build_middlewares(
     return handler
 
 
+_cached_build_middleware = lru_cache(maxsize=1024)(_build_middlewares)
+
+
 @final
 class Application(MutableMapping[Union[str, AppKey[Any]], Any]):
     __slots__ = (
@@ -397,7 +400,13 @@ async def _handle(self, request: Request) -> StreamResponse:
         handler = match_info.handler
 
         if self._run_middlewares:
-            handler = _build_middlewares(handler, match_info.apps)
+            # If its a SystemRoute, don't cache building the middlewares since
+            # they are constructed for every MatchInfoError as a new handler
+            # is made each time.
+            if isinstance(match_info.route, SystemRoute):
+                handler = _build_middlewares(handler, match_info.apps)
+            else:
+                handler = _cached_build_middleware(handler, match_info.apps)
 
         return await handler(request)
 

tests/test_web_middleware.py

@@ -4,7 +4,7 @@
 import pytest
 from yarl import URL
 
-from aiohttp import web
+from aiohttp import web, web_app
 from aiohttp.pytest_plugin import AiohttpClient
 from aiohttp.test_utils import TestClient
 from aiohttp.typedefs import Handler, Middleware
@@ -522,3 +522,26 @@ async def call(self, request: web.Request, handler: Handler) -> web.Response:
     assert 201 == resp.status
     txt = await resp.text()
     assert "OK[new style middleware]" == txt
+
+
+async def test_middleware_does_not_leak(aiohttp_client: AiohttpClient) -> None:
+    async def any_handler(request: web.Request) -> NoReturn:
+        assert False
+
+    class Middleware:
+        async def call(
+            self, request: web.Request, handler: Handler
+        ) -> web.StreamResponse:
+            return await handler(request)
+
+    app = web.Application()
+    app.router.add_route("POST", "/any", any_handler)
+    app.middlewares.append(Middleware().call)
+
+    client = await aiohttp_client(app)
+
+    web_app._cached_build_middleware.cache_clear()
+    for _ in range(10):
+        resp = await client.get("/any")
+        assert resp.status == 405
+    assert web_app._cached_build_middleware.cache_info().currsize < 10