From 6493b22b42685a6cc06c1113196d305e4d52deed Mon Sep 17 00:00:00 2001
From: Richard van der Hoff <richard@matrix.org>
Date: Fri, 27 Apr 2018 11:40:06 +0100
Subject: [PATCH] reraise exceptions more carefully

We need to be careful (under python 2, at least) that when we reraise an
exception after doing some error handling, we actually reraise the original
exception rather than anything that might have been raised (and handled) during
the error handling.
---
 synapse/handlers/federation.py | 16 ++++++++++------
 synapse/handlers/message.py    | 21 ++++++++++++++-------
 2 files changed, 24 insertions(+), 13 deletions(-)

diff --git a/synapse/handlers/federation.py b/synapse/handlers/federation.py
index ae7e0d6da208..260df025f916 100644
--- a/synapse/handlers/federation.py
+++ b/synapse/handlers/federation.py
@@ -19,9 +19,11 @@
 import httplib
 import itertools
 import logging
+import sys
 
 from signedjson.key import decode_verify_key_bytes
 from signedjson.sign import verify_signed_json
+import six
 from twisted.internet import defer
 from unpaddedbase64 import decode_base64
 
@@ -1513,12 +1515,14 @@ def _handle_new_event(self, origin, event, state=None, auth_events=None,
                 backfilled=backfilled,
             )
         except:  # noqa: E722, as we reraise the exception this is fine.
-            # Ensure that we actually remove the entries in the push actions
-            # staging area
-            logcontext.preserve_fn(
-                self.store.remove_push_actions_from_staging
-            )(event.event_id)
-            raise
+            tp, value, tb = sys.exc_info()
+
+            logcontext.run_in_background(
+                self.store.remove_push_actions_from_staging,
+                event.event_id,
+            )
+
+            six.reraise(tp, value, tb)
 
         if not backfilled:
             # this intentionally does not yield: we don't care about the result
diff --git a/synapse/handlers/message.py b/synapse/handlers/message.py
index 21628a85409c..8e2e44bdcdce 100644
--- a/synapse/handlers/message.py
+++ b/synapse/handlers/message.py
@@ -13,6 +13,12 @@
 # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 # See the License for the specific language governing permissions and
 # limitations under the License.
+import logging
+import simplejson
+import sys
+
+from canonicaljson import encode_canonical_json
+import six
 from twisted.internet import defer, reactor
 from twisted.python.failure import Failure
 
@@ -34,11 +40,6 @@
 
 from ._base import BaseHandler
 
-from canonicaljson import encode_canonical_json
-
-import logging
-import simplejson
-
 logger = logging.getLogger(__name__)
 
 
@@ -729,8 +730,14 @@ def handle_new_client_event(
         except:  # noqa: E722, as we reraise the exception this is fine.
             # Ensure that we actually remove the entries in the push actions
             # staging area, if we calculated them.
-            preserve_fn(self.store.remove_push_actions_from_staging)(event.event_id)
-            raise
+            tp, value, tb = sys.exc_info()
+
+            run_in_background(
+                self.store.remove_push_actions_from_staging,
+                event.event_id,
+            )
+
+            six.reraise(tp, value, tb)
 
     @defer.inlineCallbacks
     def persist_and_notify_client_event(