diff --git a/changelog.d/12587.misc b/changelog.d/12587.misc
new file mode 100644
index 0000000000..d26e332305
--- /dev/null
+++ b/changelog.d/12587.misc
@@ -0,0 +1 @@
+Add `@cancellable` decorator, for use on endpoint methods that can be cancelled when clients disconnect.
diff --git a/docs/usage/administration/request_log.md b/docs/usage/administration/request_log.md
index 316304c734..adb5f4f5f3 100644
--- a/docs/usage/administration/request_log.md
+++ b/docs/usage/administration/request_log.md
@@ -28,7 +28,7 @@ See the following for how to decode the dense data available from the default lo
| NNNN | Total time waiting for response to DB queries across all parallel DB work from this request |
| OOOO | Count of DB transactions performed |
| PPPP | Response body size |
-| QQQQ | Response status code (prefixed with ! if the socket was closed before the response was generated) |
+| QQQQ | Response status code<br/>Suffixed with `!` if the socket was closed before the response was generated.<br/>A `499!` status code indicates that Synapse also cancelled request processing after the socket was closed.<br/> |
| RRRR | Request |
| SSSS | User-agent |
| TTTT | Events fetched from DB to service this request (note that this does not include events fetched from the cache) |
diff --git a/synapse/http/server.py b/synapse/http/server.py
index 1cf49830e8..657bffcddd 100644
--- a/synapse/http/server.py
+++ b/synapse/http/server.py
@@ -43,6 +43,7 @@ from typing_extensions import Protocol
from zope.interface import implementer
from twisted.internet import defer, interfaces
+from twisted.internet.defer import CancelledError
from twisted.python import failure
from twisted.web import resource
from twisted.web.server import NOT_DONE_YET, Request
@@ -82,6 +83,14 @@ HTML_ERROR_TEMPLATE = """<!DOCTYPE html>
</html>
"""
+# A fictional HTTP status code for requests where the client has disconnected and we
+# successfully cancelled the request. Used only for logging purposes. Clients will never
+# observe this code unless cancellations leak across requests or we raise a
+# `CancelledError` ourselves.
+# Analogous to nginx's 499 status code:
+# https://github.com/nginx/nginx/blob/release-1.21.6/src/http/ngx_http_request.h#L128-L134
+HTTP_STATUS_REQUEST_CANCELLED = 499
+
def return_json_error(f: failure.Failure, request: SynapseRequest) -> None:
"""Sends a JSON error response to clients."""
@@ -93,6 +102,17 @@ def return_json_error(f: failure.Failure, request: SynapseRequest) -> None:
error_dict = exc.error_dict()
logger.info("%s SynapseError: %s - %s", request, error_code, exc.msg)
+ elif f.check(CancelledError):
+ error_code = HTTP_STATUS_REQUEST_CANCELLED
+ error_dict = {"error": "Request cancelled", "errcode": Codes.UNKNOWN}
+
+ if not request._disconnected:
+ logger.error(
+ "Got cancellation before client disconnection from %r: %r",
+ request.request_metrics.name,
+ request,
+ exc_info=(f.type, f.value, f.getTracebackObject()), # type: ignore[arg-type]
+ )
else:
error_code = 500
error_dict = {"error": "Internal server error", "errcode": Codes.UNKNOWN}
@@ -155,6 +175,16 @@ def return_html_error(
request,
exc_info=(f.type, f.value, f.getTracebackObject()), # type: ignore[arg-type]
)
+ elif f.check(CancelledError):
+ code = HTTP_STATUS_REQUEST_CANCELLED
+ msg = "Request cancelled"
+
+ if not request._disconnected:
+ logger.error(
+ "Got cancellation before client disconnection when handling request %r",
+ request,
+ exc_info=(f.type, f.value, f.getTracebackObject()), # type: ignore[arg-type]
+ )
else:
code = HTTPStatus.INTERNAL_SERVER_ERROR
msg = "Internal server error"
|
