From 95d38afe96bfb38e02de9767603b2655c07a7e0f Mon Sep 17 00:00:00 2001
From: Erik Johnston <erik@matrix.org>
Date: Fri, 7 Jun 2019 12:34:52 +0100
Subject: [PATCH 1/2] Don't log exception when failing to fetch remote content.

In particular, let's not log stack traces when we stop processing
becuase the response body was too large.
---
 synapse/http/client.py                    | 13 +++++++++----
 synapse/rest/media/v1/media_repository.py |  6 ++++--
 2 files changed, 13 insertions(+), 6 deletions(-)

diff --git a/synapse/http/client.py b/synapse/http/client.py
index 77fe68818b70..5c073fff07f8 100644
--- a/synapse/http/client.py
+++ b/synapse/http/client.py
@@ -17,7 +17,7 @@
 import logging
 from io import BytesIO
 
-from six import text_type
+from six import raise_from, text_type
 from six.moves import urllib
 
 import treq
@@ -542,10 +542,15 @@ def get_file(self, url, output_stream, max_size=None, headers=None):
             length = yield make_deferred_yieldable(
                 _readBodyToFile(response, output_stream, max_size)
             )
+        except SynapseError:
+            # This can happen e.g. because the body is too large.
+            raise
         except Exception as e:
-            logger.exception("Failed to download body")
-            raise SynapseError(
-                502, ("Failed to download remote body: %s" % e), Codes.UNKNOWN
+            raise_from(
+                SynapseError(
+                    502, ("Failed to download remote body: %s" % e),
+                ),
+                e
             )
 
         defer.returnValue(
diff --git a/synapse/rest/media/v1/media_repository.py b/synapse/rest/media/v1/media_repository.py
index 856967735537..a4929dd5dbd2 100644
--- a/synapse/rest/media/v1/media_repository.py
+++ b/synapse/rest/media/v1/media_repository.py
@@ -386,8 +386,10 @@ def _download_remote_file(self, server_name, media_id, file_id):
                 raise SynapseError(502, "Failed to fetch remote media")
 
             except SynapseError:
-                logger.exception("Failed to fetch remote media %s/%s",
-                                 server_name, media_id)
+                logger.warn(
+                    "Failed to fetch remote media %s/%s",
+                    server_name, media_id,
+                )
                 raise
             except NotRetryingDestination:
                 logger.warn("Not retrying destination %r", server_name)

From 5009d988da81c328d4f13fc8ceb89f85364a44bc Mon Sep 17 00:00:00 2001
From: Erik Johnston <erik@matrix.org>
Date: Fri, 7 Jun 2019 12:37:38 +0100
Subject: [PATCH 2/2] Newsfile

---
 changelog.d/5390.bugfix | 1 +
 1 file changed, 1 insertion(+)
 create mode 100644 changelog.d/5390.bugfix

diff --git a/changelog.d/5390.bugfix b/changelog.d/5390.bugfix
new file mode 100644
index 000000000000..e7b7483cf26b
--- /dev/null
+++ b/changelog.d/5390.bugfix
@@ -0,0 +1 @@
+Fix handling of failures fetching remote content to not log failures as exceptions.