Improve logging for cancelled requests (#12587)

Don't log stack traces for cancelled requests and use a custom HTTP
status code of 499.

Signed-off-by: Sean Quah <seanq@element.io>

1 files changed, 1 insertions, 1 deletions

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) |