Better request cancel handling (#2513)

sanic/exceptions.py

@@ -1,8 +1,13 @@
+from asyncio import CancelledError
 from typing import Any, Dict, Optional, Union
 
 from sanic.helpers import STATUS_CODES
 
 
+class RequestCancelled(CancelledError):
+    quiet = True
+
+
 class SanicException(Exception):
     message: str = ""
 

sanic/http/http1.py

@@ -14,8 +14,8 @@ from sanic.exceptions import (
     BadRequest,
     ExpectationFailed,
     PayloadTooLarge,
+    RequestCancelled,
     ServerError,
-    ServiceUnavailable,
 )
 from sanic.headers import format_http1_response
 from sanic.helpers import has_message_body
@@ -132,7 +132,7 @@ class Http(Stream, metaclass=TouchUpMeta):
 
                 if self.stage is Stage.RESPONSE:
                     await self.response.send(end_stream=True)
-            except CancelledError:
+            except CancelledError as exc:
                 # Write an appropriate response before exiting
                 if not self.protocol.transport:
                     logger.info(
@@ -140,7 +140,11 @@ class Http(Stream, metaclass=TouchUpMeta):
                         "stopped. Transport is closed."
                     )
                     return
-                e = self.exception or ServiceUnavailable("Cancelled")
+                e = (
+                    RequestCancelled()
+                    if self.protocol.conn_info.lost
+                    else (self.exception or exc)
+                )
                 self.exception = None
                 self.keep_alive = False
                 await self.error_response(e)

sanic/models/server_types.py

@@ -21,6 +21,7 @@ class ConnInfo:
         "client",
         "client_ip",
         "ctx",
+        "lost",
         "peername",
         "server_port",
         "server",
@@ -33,6 +34,7 @@ class ConnInfo:
 
     def __init__(self, transport: TransportProtocol, unix=None):
         self.ctx = SimpleNamespace()
+        self.lost = False
         self.peername = None
         self.server = self.client = ""
         self.server_port = self.client_port = 0

sanic/server/protocols/base_protocol.py

@@ -2,13 +2,14 @@ from __future__ import annotations
 
 from typing import TYPE_CHECKING, Optional
 
+from sanic.exceptions import RequestCancelled
+
 
 if TYPE_CHECKING:
     from sanic.app import Sanic
 
 import asyncio
 
-from asyncio import CancelledError
 from asyncio.transports import Transport
 from time import monotonic as current_time
 
@@ -69,7 +70,7 @@ class SanicProtocol(asyncio.Protocol):
         """
         await self._can_write.wait()
         if self.transport.is_closing():
-            raise CancelledError
+            raise RequestCancelled
         self.transport.write(data)
         self._time = current_time()
 
@@ -120,6 +121,7 @@ class SanicProtocol(asyncio.Protocol):
         try:
             self.connections.discard(self)
             self.resume_writing()
+            self.conn_info.lost = True
             if self._task:
                 self._task.cancel()
         except BaseException:

sanic/server/protocols/http_protocol.py

@@ -15,7 +15,11 @@ import sys
 from asyncio import CancelledError
 from time import monotonic as current_time
 
-from sanic.exceptions import RequestTimeout, ServiceUnavailable
+from sanic.exceptions import (
+    RequestCancelled,
+    RequestTimeout,
+    ServiceUnavailable,
+)
 from sanic.http import Http, Stage
 from sanic.log import Colors, error_logger, logger
 from sanic.models.server_types import ConnInfo
@@ -225,7 +229,7 @@ class HttpProtocol(HttpProtocolMixin, SanicProtocol, metaclass=TouchUpMeta):
         """
         await self._can_write.wait()
         if self.transport.is_closing():
-            raise CancelledError
+            raise RequestCancelled
         await self.app.dispatch(
             "http.lifecycle.send",
             inline=True,

tests/test_cancellederror.py

@@ -0,0 +1,21 @@
+import asyncio
+
+from asyncio import CancelledError
+
+import pytest
+
+from sanic import Request, Sanic, json
+
+
+def test_can_raise_in_handler(app: Sanic):
+    @app.get("/")
+    async def handler(request: Request):
+        raise CancelledError("STOP!!")
+
+    @app.exception(CancelledError)
+    async def handle_cancel(request: Request, exc: CancelledError):
+        return json({"message": exc.args[0]}, status=418)
+
+    _, response = app.test_client.get("/")
+    assert response.status == 418
+    assert response.json["message"] == "STOP!!"

tests/test_middleware.py

@@ -166,7 +166,7 @@ def test_middleware_response_raise_cancelled_error(app, caplog):
     with caplog.at_level(logging.ERROR):
         reqrequest, response = app.test_client.get("/")
 
-        assert response.status == 503
+        assert response.status == 500
         assert (
             "sanic.error",
             logging.ERROR,