1 files changed, 5 insertions, 0 deletions
diff --git a/synapse/http/server.py b/synapse/http/server.py
index f6d4d8db86..756c6e1aee 100644
--- a/synapse/http/server.py
+++ b/synapse/http/server.py
@@ -314,6 +314,9 @@ class HttpServer(Protocol):
         If the regex contains groups these gets passed to the callback via
         an unpacked tuple.
 
+        The callback may be marked with the `@cancellable` decorator, which will
+        cause request processing to be cancelled when clients disconnect early.
+
         Args:
             method: The HTTP method to listen to.
             path_patterns: The regex used to match requests.
@@ -544,6 +547,8 @@ 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)
+
         # Make sure we have an appropriate name for this handler in prometheus
         # (rather than the default of JsonResource).
         request.request_metrics.name = servlet_classname