[Bug Fix] Fix non-streaming request abort failure when --enable-metrics is enabled (#20625)

python/sglang/srt/utils/common.py

@@ -1344,6 +1344,12 @@ def add_prometheus_track_response_middleware(app):
         )
     )
 
+    # Fix: replace BaseHTTPMiddleware's call_next with a pure ASGI version
+    # that passes `receive` through, so request.is_disconnected() keeps working.
+    from sglang.srt.utils.http_middleware_patch import patch_app_http_middleware
+
+    patch_app_http_middleware(app)
+
     @app.middleware("http")
     async def track_http_status_code(request, call_next):
         # With recording all requests, we have the risk of high cardinality if requests have arbitrary unhandled paths.

python/sglang/srt/utils/http_middleware_patch.py

@@ -0,0 +1,67 @@
+"""
+Fix @app.middleware("http") whose BaseHTTPMiddleware call_next replaces
+ASGI ``receive``, breaking request.is_disconnected() and preventing
+non-streaming request abort on client disconnect.
+
+patch_app_http_middleware(app) replaces @app.middleware("http") with a
+version whose call_next passes ``receive`` through untouched.
+"""
+
+from __future__ import annotations
+
+from starlette.requests import Request
+
+
+class _SentResponse:
+    """Response proxy returned after the real response was already sent."""
+
+    def __init__(self, status_code: int):
+        self.status_code = status_code
+
+
+class _PureASGIDispatch:
+    """Pure ASGI middleware providing a fixed call_next that passes
+    ``receive`` through untouched (unlike BaseHTTPMiddleware)."""
+
+    def __init__(self, app, dispatch):
+        self.app = app
+        self.dispatch = dispatch
+
+    async def __call__(self, scope, receive, send):
+        if scope["type"] != "http":
+            await self.app(scope, receive, send)
+            return
+
+        request = Request(scope, receive)
+        status_code = 500
+
+        async def call_next(_request):
+            nonlocal status_code
+
+            async def send_and_capture(message):
+                nonlocal status_code
+                if message["type"] == "http.response.start":
+                    status_code = message["status"]
+                await send(message)
+
+            await self.app(scope, receive, send_and_capture)
+            return _SentResponse(status_code)
+
+        await self.dispatch(request, call_next)
+
+
+def patch_app_http_middleware(app):
+    """Replace @app.middleware("http") with a fixed-call_next version."""
+    _orig = app.middleware
+
+    def _fixed(middleware_type):
+        if middleware_type == "http":
+
+            def decorator(fn):
+                app.add_middleware(_PureASGIDispatch, dispatch=fn)
+                return fn
+
+            return decorator
+        return _orig(middleware_type)
+
+    app.middleware = _fixed