From 52aefd50860f9b44f48a9b465d42f26faa4eb84f Mon Sep 17 00:00:00 2001
From: Brendan Abolivier <babolivier@matrix.org>
Date: Thu, 7 Oct 2021 12:37:10 +0200
Subject: [PATCH] Catch AttributeErrors when calling registerProducer (#10995)

Looks like the wrong exception type was caught in #10932.
---
 changelog.d/10995.bugfix | 1 +
 synapse/http/server.py   | 5 ++++-
 2 files changed, 5 insertions(+), 1 deletion(-)
 create mode 100644 changelog.d/10995.bugfix

diff --git a/changelog.d/10995.bugfix b/changelog.d/10995.bugfix
new file mode 100644
index 0000000000..3eef96f3db
--- /dev/null
+++ b/changelog.d/10995.bugfix
@@ -0,0 +1 @@
+Correct a bugfix introduced in Synapse v1.44.0 that wouldn't catch every error of the connection breaks before a response could be written to it.
diff --git a/synapse/http/server.py b/synapse/http/server.py
index 0df1bfbeef..897ba5e453 100644
--- a/synapse/http/server.py
+++ b/synapse/http/server.py
@@ -563,7 +563,10 @@ class _ByteProducer:
 
         try:
             self._request.registerProducer(self, True)
-        except RuntimeError as e:
+        except AttributeError as e:
+            # Calling self._request.registerProducer might raise an AttributeError since
+            # the underlying Twisted code calls self._request.channel.registerProducer,
+            # however self._request.channel will be None if the connection was lost.
             logger.info("Connection disconnected before response was written: %r", e)
 
             # We drop our references to data we'll not use.