1 files changed, 3 insertions, 65 deletions
diff --git a/synapse/http/server.py b/synapse/http/server.py
index 19f42159b8..6068a94b40 100644
--- a/synapse/http/server.py
+++ b/synapse/http/server.py
@@ -33,7 +33,6 @@ from typing import (
     Optional,
     Pattern,
     Tuple,
-    TypeVar,
     Union,
 )
 
@@ -64,6 +63,7 @@ from synapse.logging.context import defer_to_thread, preserve_fn, run_in_backgro
 from synapse.logging.opentracing import active_span, start_active_span, trace_servlet
 from synapse.util import json_encoder
 from synapse.util.caches import intern_dict
+from synapse.util.cancellation import is_function_cancellable
 from synapse.util.iterutils import chunk_seq
 
 if TYPE_CHECKING:
@@ -94,68 +94,6 @@ HTML_ERROR_TEMPLATE = """<!DOCTYPE html>
 HTTP_STATUS_REQUEST_CANCELLED = 499
 
 
-F = TypeVar("F", bound=Callable[..., Any])
-
-
-_cancellable_method_names = frozenset(
-    {
-        # `RestServlet`, `BaseFederationServlet` and `BaseFederationServerServlet`
-        # methods
-        "on_GET",
-        "on_PUT",
-        "on_POST",
-        "on_DELETE",
-        # `_AsyncResource`, `DirectServeHtmlResource` and `DirectServeJsonResource`
-        # methods
-        "_async_render_GET",
-        "_async_render_PUT",
-        "_async_render_POST",
-        "_async_render_DELETE",
-        "_async_render_OPTIONS",
-        # `ReplicationEndpoint` methods
-        "_handle_request",
-    }
-)
-
-
-def cancellable(method: F) -> F:
-    """Marks a servlet method as cancellable.
-
-    Methods with this decorator will be cancelled if the client disconnects before we
-    finish processing the request.
-
-    During cancellation, `Deferred.cancel()` will be invoked on the `Deferred` wrapping
-    the method. The `cancel()` call will propagate down to the `Deferred` that is
-    currently being waited on. That `Deferred` will raise a `CancelledError`, which will
-    propagate up, as per normal exception handling.
-
-    Before applying this decorator to a new endpoint, you MUST recursively check
-    that all `await`s in the function are on `async` functions or `Deferred`s that
-    handle cancellation cleanly, otherwise a variety of bugs may occur, ranging from
-    premature logging context closure, to stuck requests, to database corruption.
-
-    Usage:
-        class SomeServlet(RestServlet):
-            @cancellable
-            async def on_GET(self, request: SynapseRequest) -> ...:
-                ...
-    """
-    if method.__name__ not in _cancellable_method_names and not any(
-        method.__name__.startswith(prefix) for prefix in _cancellable_method_names
-    ):
-        raise ValueError(
-            "@cancellable decorator can only be applied to servlet methods."
-        )
-
-    method.cancellable = True  # type: ignore[attr-defined]
-    return method
-
-
-def is_method_cancellable(method: Callable[..., Any]) -> bool:
-    """Checks whether a servlet method has the `@cancellable` flag."""
-    return getattr(method, "cancellable", False)
-
-
 def return_json_error(
     f: failure.Failure, request: SynapseRequest, config: Optional[HomeServerConfig]
 ) -> None:
@@ -389,7 +327,7 @@ class _AsyncResource(resource.Resource, metaclass=abc.ABCMeta):
 
         method_handler = getattr(self, "_async_render_%s" % (request_method,), None)
         if method_handler:
-            request.is_render_cancellable = is_method_cancellable(method_handler)
+            request.is_render_cancellable = is_function_cancellable(method_handler)
 
             raw_callback_return = method_handler(request)
 
@@ -551,7 +489,7 @@ class JsonResource(DirectServeJsonResource):
     async def _async_render(self, request: SynapseRequest) -> Tuple[int, Any]:
         callback, servlet_classname, group_dict = self._get_handler_for_request(request)
 
-        request.is_render_cancellable = is_method_cancellable(callback)
+        request.is_render_cancellable = is_function_cancellable(callback)
 
         # Make sure we have an appropriate name for this handler in prometheus
         # (rather than the default of JsonResource).