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authorErik Johnston <erik@matrix.org>2017-04-04 09:46:16 +0100
committerErik Johnston <erik@matrix.org>2017-04-04 09:46:16 +0100
commit62b89daac6f4418d831d531fa40ad71aa0c74fb9 (patch)
treea5fa797ac7e65f85cae52cccd88451e5672257c6
parentAlways advance stream tokens (diff)
parentMerge pull request #2095 from matrix-org/rav/cull_log_preserves (diff)
downloadsynapse-62b89daac6f4418d831d531fa40ad71aa0c74fb9.tar.xz
Merge branch 'develop' of github.com:matrix-org/synapse into erikj/repl_tcp_server
Diffstat (limited to '')
-rw-r--r--CHANGES.rst44
-rw-r--r--README.rst4
-rw-r--r--docs/log_contexts.rst11
-rw-r--r--docs/postgres.rst6
-rw-r--r--docs/turn-howto.rst38
-rwxr-xr-xscripts-dev/nuke-room-from-db.sh43
-rwxr-xr-xscripts/synapse_port_db4
-rw-r--r--synapse/__init__.py2
-rwxr-xr-xsynapse/app/synctl.py3
-rw-r--r--synapse/appservice/__init__.py38
-rw-r--r--synapse/config/voip.py8
-rw-r--r--synapse/federation/federation_server.py8
-rw-r--r--synapse/handlers/federation.py59
-rw-r--r--synapse/handlers/message.py2
-rw-r--r--synapse/notifier.py23
-rw-r--r--synapse/push/push_rule_evaluator.py104
-rw-r--r--synapse/push/push_tools.py7
-rw-r--r--synapse/rest/client/v1/voip.py5
-rw-r--r--synapse/rest/client/v2_alpha/thirdparty.py8
-rw-r--r--synapse/types.py4
-rw-r--r--synapse/util/async.py7
-rw-r--r--synapse/util/caches/descriptors.py70
-rw-r--r--synapse/util/logcontext.py29
-rw-r--r--synapse/visibility.py3
-rw-r--r--tests/appservice/test_appservice.py4
-rw-r--r--tests/storage/test__base.py2
-rw-r--r--tests/util/caches/test_descriptors.py129
-rw-r--r--tests/util/test_snapshot_cache.py4
28 files changed, 489 insertions, 180 deletions
diff --git a/CHANGES.rst b/CHANGES.rst
index 2a46af52a8..6659c6671a 100644
--- a/CHANGES.rst
+++ b/CHANGES.rst
@@ -1,3 +1,47 @@
+Changes in synapse v0.20.0-rc1 (2017-03-30)
+===========================================
+
+Features:
+
+* Add delete_devices API (PR #1993)
+* Add phone number registration/login support (PR #1994, #2055)
+
+
+Changes:
+
+* Use JSONSchema for validation of filters. Thanks @pik! (PR #1783)
+* Reread log config on SIGHUP (PR #1982)
+* Speed up public room list (PR #1989)
+* Add helpful texts to logger config options (PR #1990)
+* Minor ``/sync`` performance improvements. (PR #2002, #2013, #2022)
+* Add some debug to help diagnose weird federation issue (PR #2035)
+* Correctly limit retries for all federation requests (PR #2050, #2061)
+* Don't lock table when persisting new one time keys (PR #2053)
+* Reduce some CPU work on DB threads (PR #2054)
+* Cache hosts in room (PR #2060)
+* Batch sending of device list pokes (PR #2063)
+* Speed up persist event path in certain edge cases (PR #2070)
+
+
+Bug fixes:
+
+* Fix bug where current_state_events renamed to current_state_ids (PR #1849)
+* Fix routing loop when fetching remote media (PR #1992)
+* Fix current_state_events table to not lie (PR #1996)
+* Fix CAS login to handle PartialDownloadError (PR #1997)
+* Fix assertion to stop transaction queue getting wedged (PR #2010)
+* Fix presence to fallback to last_active_ts if it beats the last sync time.
+  Thanks @Half-Shot! (PR #2014)
+* Fix bug when federation received a PDU while a room join is in progress (PR
+  #2016)
+* Fix resetting state on rejected events (PR #2025)
+* Fix installation issues in readme. Thanks @ricco386 (PR #2037)
+* Fix caching of remote servers' signature keys (PR #2042)
+* Fix some leaking log context (PR #2048, #2049, #2057, #2058)
+* Fix rejection of invites not reaching sync (PR #2056)
+
+
+
 Changes in synapse v0.19.3 (2017-03-20)
 =======================================
 
diff --git a/README.rst b/README.rst
index b9c854ad48..759197f5ff 100644
--- a/README.rst
+++ b/README.rst
@@ -108,10 +108,10 @@ Installing prerequisites on ArchLinux::
     sudo pacman -S base-devel python2 python-pip \
                    python-setuptools python-virtualenv sqlite3
 
-Installing prerequisites on CentOS 7::
+Installing prerequisites on CentOS 7 or Fedora 25::
 
     sudo yum install libtiff-devel libjpeg-devel libzip-devel freetype-devel \
-                     lcms2-devel libwebp-devel tcl-devel tk-devel \
+                     lcms2-devel libwebp-devel tcl-devel tk-devel redhat-rpm-config \
                      python-virtualenv libffi-devel openssl-devel
     sudo yum groupinstall "Development Tools"
 
diff --git a/docs/log_contexts.rst b/docs/log_contexts.rst
index 8d04a973de..eb1784e700 100644
--- a/docs/log_contexts.rst
+++ b/docs/log_contexts.rst
@@ -204,9 +204,14 @@ That doesn't follow the rules, but we can fix it by wrapping it with
 This technique works equally for external functions which return deferreds,
 or deferreds we have made ourselves.
 
-XXX: think this is what ``preserve_context_over_deferred`` is supposed to do,
-though it is broken, in that it only restores the logcontext for the duration
-of the callbacks, which doesn't comply with the logcontext rules.
+You can also use ``logcontext.make_deferred_yieldable``, which just does the
+boilerplate for you, so the above could be written:
+
+.. code:: python
+
+    def sleep(seconds):
+        return logcontext.make_deferred_yieldable(get_sleep_deferred(seconds))
+
 
 Fire-and-forget
 ---------------
diff --git a/docs/postgres.rst b/docs/postgres.rst
index 402ff9a4de..b592801e93 100644
--- a/docs/postgres.rst
+++ b/docs/postgres.rst
@@ -112,9 +112,9 @@ script one last time, e.g. if the SQLite database is at  ``homeserver.db``
 run::
 
     synapse_port_db --sqlite-database homeserver.db \
-        --postgres-config database_config.yaml
+        --postgres-config homeserver-postgres.yaml
 
 Once that has completed, change the synapse config to point at the PostgreSQL
-database configuration file using the ``database_config`` parameter (see
-`Synapse Config`_) and restart synapse. Synapse should now be running against
+database configuration file ``homeserver-postgres.yaml`` (i.e. rename it to 
+``homeserver.yaml``) and restart synapse. Synapse should now be running against
 PostgreSQL.
diff --git a/docs/turn-howto.rst b/docs/turn-howto.rst
index 04c0100715..e48628ce6e 100644
--- a/docs/turn-howto.rst
+++ b/docs/turn-howto.rst
@@ -50,14 +50,37 @@ You may be able to setup coturn via your package manager,  or set it up manually
 
        pwgen -s 64 1
 
- 5. Ensure youe firewall allows traffic into the TURN server on
+ 5. Consider your security settings.  TURN lets users request a relay
+    which will connect to arbitrary IP addresses and ports.  At the least
+    we recommend:
+
+       # VoIP traffic is all UDP. There is no reason to let users connect to arbitrary TCP endpoints via the relay.
+       no-tcp-relay
+
+       # don't let the relay ever try to connect to private IP address ranges within your network (if any)
+       # given the turn server is likely behind your firewall, remember to include any privileged public IPs too.
+       denied-peer-ip=10.0.0.0-10.255.255.255
+       denied-peer-ip=192.168.0.0-192.168.255.255
+       denied-peer-ip=172.16.0.0-172.31.255.255
+
+       # special case the turn server itself so that client->TURN->TURN->client flows work
+       allowed-peer-ip=10.0.0.1
+
+       # consider whether you want to limit the quota of relayed streams per user (or total) to avoid risk of DoS.
+       user-quota=12 # 4 streams per video call, so 12 streams = 3 simultaneous relayed calls per user.
+       total-quota=1200
+
+    Ideally coturn should refuse to relay traffic which isn't SRTP;
+    see https://github.com/matrix-org/synapse/issues/2009
+
+ 6. Ensure your firewall allows traffic into the TURN server on
     the ports you've configured it to listen on (remember to allow
-    both TCP and UDP if you've enabled both).
+    both TCP and UDP TURN traffic)
 
- 6. If you've configured coturn to support TLS/DTLS, generate or
+ 7. If you've configured coturn to support TLS/DTLS, generate or
     import your private key and certificate.
 
- 7. Start the turn server::
+ 8. Start the turn server::
  
        bin/turnserver -o
 
@@ -83,12 +106,19 @@ Your home server configuration file needs the following extra keys:
     to refresh credentials. The TURN REST API specification recommends
     one day (86400000).
 
+  4. "turn_allow_guests": Whether to allow guest users to use the TURN
+    server.  This is enabled by default, as otherwise VoIP will not
+    work reliably for guests.  However, it does introduce a security risk
+    as it lets guests connect to arbitrary endpoints without having gone
+    through a CAPTCHA or similar to register a real account.
+
 As an example, here is the relevant section of the config file for
 matrix.org::
 
     turn_uris: [ "turn:turn.matrix.org:3478?transport=udp", "turn:turn.matrix.org:3478?transport=tcp" ]
     turn_shared_secret: n0t4ctuAllymatr1Xd0TorgSshar3d5ecret4obvIousreAsons
     turn_user_lifetime: 86400000
+    turn_allow_guests: True
 
 Now, restart synapse::
 
diff --git a/scripts-dev/nuke-room-from-db.sh b/scripts-dev/nuke-room-from-db.sh
index 58c036c896..1201d176c2 100755
--- a/scripts-dev/nuke-room-from-db.sh
+++ b/scripts-dev/nuke-room-from-db.sh
@@ -9,16 +9,39 @@
 ROOMID="$1"
 
 sqlite3 homeserver.db <<EOF
-DELETE FROM context_depth WHERE context = '$ROOMID';
-DELETE FROM current_state WHERE context = '$ROOMID';
-DELETE FROM feedback WHERE room_id = '$ROOMID';
-DELETE FROM messages WHERE room_id = '$ROOMID';
-DELETE FROM pdu_backward_extremities WHERE context = '$ROOMID';
-DELETE FROM pdu_edges WHERE context = '$ROOMID';
-DELETE FROM pdu_forward_extremities WHERE context = '$ROOMID';
-DELETE FROM pdus WHERE context = '$ROOMID';
-DELETE FROM room_data WHERE room_id = '$ROOMID';
+DELETE FROM event_forward_extremities WHERE room_id = '$ROOMID';
+DELETE FROM event_backward_extremities WHERE room_id = '$ROOMID';
+DELETE FROM event_edges WHERE room_id = '$ROOMID';
+DELETE FROM room_depth WHERE room_id = '$ROOMID';
+DELETE FROM state_forward_extremities WHERE room_id = '$ROOMID';
+DELETE FROM events WHERE room_id = '$ROOMID';
+DELETE FROM event_json WHERE room_id = '$ROOMID';
+DELETE FROM state_events WHERE room_id = '$ROOMID';
+DELETE FROM current_state_events WHERE room_id = '$ROOMID';
 DELETE FROM room_memberships WHERE room_id = '$ROOMID';
+DELETE FROM feedback WHERE room_id = '$ROOMID';
+DELETE FROM topics WHERE room_id = '$ROOMID';
+DELETE FROM room_names WHERE room_id = '$ROOMID';
 DELETE FROM rooms WHERE room_id = '$ROOMID';
-DELETE FROM state_pdus WHERE context = '$ROOMID';
+DELETE FROM room_hosts WHERE room_id = '$ROOMID';
+DELETE FROM room_aliases WHERE room_id = '$ROOMID';
+DELETE FROM state_groups WHERE room_id = '$ROOMID';
+DELETE FROM state_groups_state WHERE room_id = '$ROOMID';
+DELETE FROM receipts_graph WHERE room_id = '$ROOMID';
+DELETE FROM receipts_linearized WHERE room_id = '$ROOMID';
+DELETE FROM event_search_content WHERE c1room_id = '$ROOMID';
+DELETE FROM guest_access WHERE room_id = '$ROOMID';
+DELETE FROM history_visibility WHERE room_id = '$ROOMID';
+DELETE FROM room_tags WHERE room_id = '$ROOMID';
+DELETE FROM room_tags_revisions WHERE room_id = '$ROOMID';
+DELETE FROM room_account_data WHERE room_id = '$ROOMID';
+DELETE FROM event_push_actions WHERE room_id = '$ROOMID';
+DELETE FROM local_invites WHERE room_id = '$ROOMID';
+DELETE FROM pusher_throttle WHERE room_id = '$ROOMID';
+DELETE FROM event_reports WHERE room_id = '$ROOMID';
+DELETE FROM public_room_list_stream WHERE room_id = '$ROOMID';
+DELETE FROM stream_ordering_to_exterm WHERE room_id = '$ROOMID';
+DELETE FROM event_auth WHERE room_id = '$ROOMID';
+DELETE FROM appservice_room_list WHERE room_id = '$ROOMID';
+VACUUM;
 EOF
diff --git a/scripts/synapse_port_db b/scripts/synapse_port_db
index ea367a1281..2e5d666707 100755
--- a/scripts/synapse_port_db
+++ b/scripts/synapse_port_db
@@ -447,9 +447,7 @@ class Porter(object):
 
             postgres_tables = yield self.postgres_store._simple_select_onecol(
                 table="information_schema.tables",
-                keyvalues={
-                    "table_schema": "public",
-                },
+                keyvalues={},
                 retcol="distinct table_name",
             )
 
diff --git a/synapse/__init__.py b/synapse/__init__.py
index 7628e7c505..580927abf4 100644
--- a/synapse/__init__.py
+++ b/synapse/__init__.py
@@ -16,4 +16,4 @@
 """ This is a reference implementation of a Matrix home server.
 """
 
-__version__ = "0.19.3"
+__version__ = "0.20.0-rc1"
diff --git a/synapse/app/synctl.py b/synapse/app/synctl.py
index 23eb6a1ec4..e8218d01ad 100755
--- a/synapse/app/synctl.py
+++ b/synapse/app/synctl.py
@@ -202,7 +202,8 @@ def main():
         worker_app = worker_config["worker_app"]
         worker_pidfile = worker_config["worker_pid_file"]
         worker_daemonize = worker_config["worker_daemonize"]
-        assert worker_daemonize  # TODO print something more user friendly
+        assert worker_daemonize, "In config %r: expected '%s' to be True" % (
+            worker_configfile, "worker_daemonize")
         worker_cache_factor = worker_config.get("synctl_cache_factor")
         workers.append(Worker(
             worker_app, worker_configfile, worker_pidfile, worker_cache_factor,
diff --git a/synapse/appservice/__init__.py b/synapse/appservice/__init__.py
index b0106a3597..7346206bb1 100644
--- a/synapse/appservice/__init__.py
+++ b/synapse/appservice/__init__.py
@@ -13,6 +13,7 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 from synapse.api.constants import EventTypes
+from synapse.util.caches.descriptors import cachedInlineCallbacks
 
 from twisted.internet import defer
 
@@ -124,29 +125,23 @@ class ApplicationService(object):
                     raise ValueError(
                         "Expected bool for 'exclusive' in ns '%s'" % ns
                     )
-                if not isinstance(regex_obj.get("regex"), basestring):
+                regex = regex_obj.get("regex")
+                if isinstance(regex, basestring):
+                    regex_obj["regex"] = re.compile(regex)  # Pre-compile regex
+                else:
                     raise ValueError(
                         "Expected string for 'regex' in ns '%s'" % ns
                     )
         return namespaces
 
-    def _matches_regex(self, test_string, namespace_key, return_obj=False):
-        if not isinstance(test_string, basestring):
-            logger.error(
-                "Expected a string to test regex against, but got %s",
-                test_string
-            )
-            return False
-
+    def _matches_regex(self, test_string, namespace_key):
         for regex_obj in self.namespaces[namespace_key]:
-            if re.match(regex_obj["regex"], test_string):
-                if return_obj:
-                    return regex_obj
-                return True
-        return False
+            if regex_obj["regex"].match(test_string):
+                return regex_obj
+        return None
 
     def _is_exclusive(self, ns_key, test_string):
-        regex_obj = self._matches_regex(test_string, ns_key, return_obj=True)
+        regex_obj = self._matches_regex(test_string, ns_key)
         if regex_obj:
             return regex_obj["exclusive"]
         return False
@@ -166,7 +161,14 @@ class ApplicationService(object):
         if not store:
             defer.returnValue(False)
 
-        member_list = yield store.get_users_in_room(event.room_id)
+        does_match = yield self._matches_user_in_member_list(event.room_id, store)
+        defer.returnValue(does_match)
+
+    @cachedInlineCallbacks(num_args=1, cache_context=True)
+    def _matches_user_in_member_list(self, room_id, store, cache_context):
+        member_list = yield store.get_users_in_room(
+            room_id, on_invalidate=cache_context.invalidate
+        )
 
         # check joined member events
         for user_id in member_list:
@@ -219,10 +221,10 @@ class ApplicationService(object):
         )
 
     def is_interested_in_alias(self, alias):
-        return self._matches_regex(alias, ApplicationService.NS_ALIASES)
+        return bool(self._matches_regex(alias, ApplicationService.NS_ALIASES))
 
     def is_interested_in_room(self, room_id):
-        return self._matches_regex(room_id, ApplicationService.NS_ROOMS)
+        return bool(self._matches_regex(room_id, ApplicationService.NS_ROOMS))
 
     def is_exclusive_user(self, user_id):
         return (
diff --git a/synapse/config/voip.py b/synapse/config/voip.py
index eeb693027b..3a4e16fa96 100644
--- a/synapse/config/voip.py
+++ b/synapse/config/voip.py
@@ -23,6 +23,7 @@ class VoipConfig(Config):
         self.turn_username = config.get("turn_username")
         self.turn_password = config.get("turn_password")
         self.turn_user_lifetime = self.parse_duration(config["turn_user_lifetime"])
+        self.turn_allow_guests = config.get("turn_allow_guests", True)
 
     def default_config(self, **kwargs):
         return """\
@@ -41,4 +42,11 @@ class VoipConfig(Config):
 
         # How long generated TURN credentials last
         turn_user_lifetime: "1h"
+
+        # Whether guests should be allowed to use the TURN server.
+        # This defaults to True, otherwise VoIP will be unreliable for guests.
+        # However, it does introduce a slight security risk as it allows users to
+        # connect to arbitrary endpoints without having first signed up for a
+        # valid account (e.g. by passing a CAPTCHA).
+        turn_allow_guests: True
         """
diff --git a/synapse/federation/federation_server.py b/synapse/federation/federation_server.py
index 510a176821..bc20b9c201 100644
--- a/synapse/federation/federation_server.py
+++ b/synapse/federation/federation_server.py
@@ -146,11 +146,15 @@ class FederationServer(FederationBase):
             # check that it's actually being sent from a valid destination to
             # workaround bug #1753 in 0.18.5 and 0.18.6
             if transaction.origin != get_domain_from_id(pdu.event_id):
+                # We continue to accept join events from any server; this is
+                # necessary for the federation join dance to work correctly.
+                # (When we join over federation, the "helper" server is
+                # responsible for sending out the join event, rather than the
+                # origin. See bug #1893).
                 if not (
                     pdu.type == 'm.room.member' and
                     pdu.content and
-                    pdu.content.get("membership", None) == 'join' and
-                    self.hs.is_mine_id(pdu.state_key)
+                    pdu.content.get("membership", None) == 'join'
                 ):
                     logger.info(
                         "Discarding PDU %s from invalid origin %s",
diff --git a/synapse/handlers/federation.py b/synapse/handlers/federation.py
index 888dd01240..6ed5ce9e10 100644
--- a/synapse/handlers/federation.py
+++ b/synapse/handlers/federation.py
@@ -28,7 +28,7 @@ from synapse.api.constants import EventTypes, Membership, RejectedReason
 from synapse.events.validator import EventValidator
 from synapse.util import unwrapFirstError
 from synapse.util.logcontext import (
-    PreserveLoggingContext, preserve_fn, preserve_context_over_deferred
+    preserve_fn, preserve_context_over_deferred
 )
 from synapse.util.metrics import measure_func
 from synapse.util.logutils import log_function
@@ -394,11 +394,10 @@ class FederationHandler(BaseHandler):
             target_user = UserID.from_string(target_user_id)
             extra_users.append(target_user)
 
-        with PreserveLoggingContext():
-            self.notifier.on_new_room_event(
-                event, event_stream_id, max_stream_id,
-                extra_users=extra_users
-            )
+        self.notifier.on_new_room_event(
+            event, event_stream_id, max_stream_id,
+            extra_users=extra_users
+        )
 
         if event.type == EventTypes.Member:
             if event.membership == Membership.JOIN:
@@ -916,11 +915,10 @@ class FederationHandler(BaseHandler):
                 origin, auth_chain, state, event
             )
 
-            with PreserveLoggingContext():
-                self.notifier.on_new_room_event(
-                    event, event_stream_id, max_stream_id,
-                    extra_users=[joinee]
-                )
+            self.notifier.on_new_room_event(
+                event, event_stream_id, max_stream_id,
+                extra_users=[joinee]
+            )
 
             logger.debug("Finished joining %s to %s", joinee, room_id)
         finally:
@@ -1004,9 +1002,19 @@ class FederationHandler(BaseHandler):
         )
 
         event.internal_metadata.outlier = False
-        # Send this event on behalf of the origin server since they may not
-        # have an up to data view of the state of the room at this event so
-        # will not know which servers to send the event to.
+        # Send this event on behalf of the origin server.
+        #
+        # The reasons we have the destination server rather than the origin
+        # server send it are slightly mysterious: the origin server should have
+        # all the neccessary state once it gets the response to the send_join,
+        # so it could send the event itself if it wanted to. It may be that
+        # doing it this way reduces failure modes, or avoids certain attacks
+        # where a new server selectively tells a subset of the federation that
+        # it has joined.
+        #
+        # The fact is that, as of the current writing, Synapse doesn't send out
+        # the join event over federation after joining, and changing it now
+        # would introduce the danger of backwards-compatibility problems.
         event.internal_metadata.send_on_behalf_of = origin
 
         context, event_stream_id, max_stream_id = yield self._handle_new_event(
@@ -1025,10 +1033,9 @@ class FederationHandler(BaseHandler):
             target_user = UserID.from_string(target_user_id)
             extra_users.append(target_user)
 
-        with PreserveLoggingContext():
-            self.notifier.on_new_room_event(
-                event, event_stream_id, max_stream_id, extra_users=extra_users
-            )
+        self.notifier.on_new_room_event(
+            event, event_stream_id, max_stream_id, extra_users=extra_users
+        )
 
         if event.type == EventTypes.Member:
             if event.content["membership"] == Membership.JOIN:
@@ -1074,11 +1081,10 @@ class FederationHandler(BaseHandler):
         )
 
         target_user = UserID.from_string(event.state_key)
-        with PreserveLoggingContext():
-            self.notifier.on_new_room_event(
-                event, event_stream_id, max_stream_id,
-                extra_users=[target_user],
-            )
+        self.notifier.on_new_room_event(
+            event, event_stream_id, max_stream_id,
+            extra_users=[target_user],
+        )
 
         defer.returnValue(event)
 
@@ -1236,10 +1242,9 @@ class FederationHandler(BaseHandler):
             target_user = UserID.from_string(target_user_id)
             extra_users.append(target_user)
 
-        with PreserveLoggingContext():
-            self.notifier.on_new_room_event(
-                event, event_stream_id, max_stream_id, extra_users=extra_users
-            )
+        self.notifier.on_new_room_event(
+            event, event_stream_id, max_stream_id, extra_users=extra_users
+        )
 
         defer.returnValue(None)
 
diff --git a/synapse/handlers/message.py b/synapse/handlers/message.py
index 7a498af5a2..348056add5 100644
--- a/synapse/handlers/message.py
+++ b/synapse/handlers/message.py
@@ -612,7 +612,7 @@ class MessageHandler(BaseHandler):
         @defer.inlineCallbacks
         def _notify():
             yield run_on_reactor()
-            yield self.notifier.on_new_room_event(
+            self.notifier.on_new_room_event(
                 event, event_stream_id, max_stream_id,
                 extra_users=extra_users
             )
diff --git a/synapse/notifier.py b/synapse/notifier.py
index 4fda184b7a..48566187ab 100644
--- a/synapse/notifier.py
+++ b/synapse/notifier.py
@@ -210,7 +210,6 @@ class Notifier(object):
         """
         self.replication_callbacks.append(cb)
 
-    @preserve_fn
     def on_new_room_event(self, event, room_stream_id, max_room_stream_id,
                           extra_users=[]):
         """ Used by handlers to inform the notifier something has happened
@@ -224,15 +223,13 @@ class Notifier(object):
         until all previous events have been persisted before notifying
         the client streams.
         """
-        with PreserveLoggingContext():
-            self.pending_new_room_events.append((
-                room_stream_id, event, extra_users
-            ))
-            self._notify_pending_new_room_events(max_room_stream_id)
+        self.pending_new_room_events.append((
+            room_stream_id, event, extra_users
+        ))
+        self._notify_pending_new_room_events(max_room_stream_id)
 
-            self.notify_replication()
+        self.notify_replication()
 
-    @preserve_fn
     def _notify_pending_new_room_events(self, max_room_stream_id):
         """Notify for the room events that were queued waiting for a previous
         event to be persisted.
@@ -250,14 +247,16 @@ class Notifier(object):
             else:
                 self._on_new_room_event(event, room_stream_id, extra_users)
 
-    @preserve_fn
     def _on_new_room_event(self, event, room_stream_id, extra_users=[]):
         """Notify any user streams that are interested in this room event"""
         # poke any interested application service.
-        self.appservice_handler.notify_interested_services(room_stream_id)
+        preserve_fn(self.appservice_handler.notify_interested_services)(
+            room_stream_id)
 
         if self.federation_sender:
-            self.federation_sender.notify_new_events(room_stream_id)
+            preserve_fn(self.federation_sender.notify_new_events)(
+                room_stream_id
+            )
 
         if event.type == EventTypes.Member and event.membership == Membership.JOIN:
             self._user_joined_room(event.state_key, event.room_id)
@@ -268,7 +267,6 @@ class Notifier(object):
             rooms=[event.room_id],
         )
 
-    @preserve_fn
     def on_new_event(self, stream_key, new_token, users=[], rooms=[]):
         """ Used to inform listeners that something has happend event wise.
 
@@ -295,7 +293,6 @@ class Notifier(object):
 
                 self.notify_replication()
 
-    @preserve_fn
     def on_new_replication_data(self):
         """Used to inform replication listeners that something has happend
         without waking up any of the normal user event streams"""
diff --git a/synapse/push/push_rule_evaluator.py b/synapse/push/push_rule_evaluator.py
index 4db76f18bd..4d88046579 100644
--- a/synapse/push/push_rule_evaluator.py
+++ b/synapse/push/push_rule_evaluator.py
@@ -17,6 +17,7 @@ import logging
 import re
 
 from synapse.types import UserID
+from synapse.util.caches import CACHE_SIZE_FACTOR, register_cache
 from synapse.util.caches.lrucache import LruCache
 
 logger = logging.getLogger(__name__)
@@ -125,6 +126,11 @@ class PushRuleEvaluatorForEvent(object):
         return self._value_cache.get(dotted_key, None)
 
 
+# Caches (glob, word_boundary) -> regex for push. See _glob_matches
+regex_cache = LruCache(50000 * CACHE_SIZE_FACTOR)
+register_cache("regex_push_cache", regex_cache)
+
+
 def _glob_matches(glob, value, word_boundary=False):
     """Tests if value matches glob.
 
@@ -137,46 +143,63 @@ def _glob_matches(glob, value, word_boundary=False):
     Returns:
         bool
     """
-    try:
-        if IS_GLOB.search(glob):
-            r = re.escape(glob)
-
-            r = r.replace(r'\*', '.*?')
-            r = r.replace(r'\?', '.')
-
-            # handle [abc], [a-z] and [!a-z] style ranges.
-            r = GLOB_REGEX.sub(
-                lambda x: (
-                    '[%s%s]' % (
-                        x.group(1) and '^' or '',
-                        x.group(2).replace(r'\\\-', '-')
-                    )
-                ),
-                r,
-            )
-            if word_boundary:
-                r = r"\b%s\b" % (r,)
-                r = _compile_regex(r)
-
-                return r.search(value)
-            else:
-                r = r + "$"
-                r = _compile_regex(r)
-
-                return r.match(value)
-        elif word_boundary:
-            r = re.escape(glob)
-            r = r"\b%s\b" % (r,)
-            r = _compile_regex(r)
 
-            return r.search(value)
-        else:
-            return value.lower() == glob.lower()
+    try:
+        r = regex_cache.get((glob, word_boundary), None)
+        if not r:
+            r = _glob_to_re(glob, word_boundary)
+            regex_cache[(glob, word_boundary)] = r
+        return r.search(value)
     except re.error:
         logger.warn("Failed to parse glob to regex: %r", glob)
         return False
 
 
+def _glob_to_re(glob, word_boundary):
+    """Generates regex for a given glob.
+
+    Args:
+        glob (string)
+        word_boundary (bool): Whether to match against word boundaries or entire
+            string. Defaults to False.
+
+    Returns:
+        regex object
+    """
+    if IS_GLOB.search(glob):
+        r = re.escape(glob)
+
+        r = r.replace(r'\*', '.*?')
+        r = r.replace(r'\?', '.')
+
+        # handle [abc], [a-z] and [!a-z] style ranges.
+        r = GLOB_REGEX.sub(
+            lambda x: (
+                '[%s%s]' % (
+                    x.group(1) and '^' or '',
+                    x.group(2).replace(r'\\\-', '-')
+                )
+            ),
+            r,
+        )
+        if word_boundary:
+            r = r"\b%s\b" % (r,)
+
+            return re.compile(r, flags=re.IGNORECASE)
+        else:
+            r = "^" + r + "$"
+
+            return re.compile(r, flags=re.IGNORECASE)
+    elif word_boundary:
+        r = re.escape(glob)
+        r = r"\b%s\b" % (r,)
+
+        return re.compile(r, flags=re.IGNORECASE)
+    else:
+        r = "^" + re.escape(glob) + "$"
+        return re.compile(r, flags=re.IGNORECASE)
+
+
 def _flatten_dict(d, prefix=[], result={}):
     for key, value in d.items():
         if isinstance(value, basestring):
@@ -185,16 +208,3 @@ def _flatten_dict(d, prefix=[], result={}):
             _flatten_dict(value, prefix=(prefix + [key]), result=result)
 
     return result
-
-
-regex_cache = LruCache(5000)
-
-
-def _compile_regex(regex_str):
-    r = regex_cache.get(regex_str, None)
-    if r:
-        return r
-
-    r = re.compile(regex_str, flags=re.IGNORECASE)
-    regex_cache[regex_str] = r
-    return r
diff --git a/synapse/push/push_tools.py b/synapse/push/push_tools.py
index 287df94b4f..6835f54e97 100644
--- a/synapse/push/push_tools.py
+++ b/synapse/push/push_tools.py
@@ -17,15 +17,12 @@ from twisted.internet import defer
 from synapse.push.presentable_names import (
     calculate_room_name, name_from_member_event
 )
-from synapse.util.logcontext import preserve_fn, preserve_context_over_deferred
 
 
 @defer.inlineCallbacks
 def get_badge_count(store, user_id):
-    invites, joins = yield preserve_context_over_deferred(defer.gatherResults([
-        preserve_fn(store.get_invited_rooms_for_user)(user_id),
-        preserve_fn(store.get_rooms_for_user)(user_id),
-    ], consumeErrors=True))
+    invites = yield store.get_invited_rooms_for_user(user_id)
+    joins = yield store.get_rooms_for_user(user_id)
 
     my_receipts_by_room = yield store.get_receipts_for_user(
         user_id, "m.read",
diff --git a/synapse/rest/client/v1/voip.py b/synapse/rest/client/v1/voip.py
index 03141c623c..c43b30b73a 100644
--- a/synapse/rest/client/v1/voip.py
+++ b/synapse/rest/client/v1/voip.py
@@ -28,7 +28,10 @@ class VoipRestServlet(ClientV1RestServlet):
 
     @defer.inlineCallbacks
     def on_GET(self, request):
-        requester = yield self.auth.get_user_by_req(request)
+        requester = yield self.auth.get_user_by_req(
+            request,
+            self.hs.config.turn_allow_guests
+        )
 
         turnUris = self.hs.config.turn_uris
         turnSecret = self.hs.config.turn_shared_secret
diff --git a/synapse/rest/client/v2_alpha/thirdparty.py b/synapse/rest/client/v2_alpha/thirdparty.py
index 31f94bc6e9..6fceb23e26 100644
--- a/synapse/rest/client/v2_alpha/thirdparty.py
+++ b/synapse/rest/client/v2_alpha/thirdparty.py
@@ -36,7 +36,7 @@ class ThirdPartyProtocolsServlet(RestServlet):
 
     @defer.inlineCallbacks
     def on_GET(self, request):
-        yield self.auth.get_user_by_req(request)
+        yield self.auth.get_user_by_req(request, allow_guest=True)
 
         protocols = yield self.appservice_handler.get_3pe_protocols()
         defer.returnValue((200, protocols))
@@ -54,7 +54,7 @@ class ThirdPartyProtocolServlet(RestServlet):
 
     @defer.inlineCallbacks
     def on_GET(self, request, protocol):
-        yield self.auth.get_user_by_req(request)
+        yield self.auth.get_user_by_req(request, allow_guest=True)
 
         protocols = yield self.appservice_handler.get_3pe_protocols(
             only_protocol=protocol,
@@ -77,7 +77,7 @@ class ThirdPartyUserServlet(RestServlet):
 
     @defer.inlineCallbacks
     def on_GET(self, request, protocol):
-        yield self.auth.get_user_by_req(request)
+        yield self.auth.get_user_by_req(request, allow_guest=True)
 
         fields = request.args
         fields.pop("access_token", None)
@@ -101,7 +101,7 @@ class ThirdPartyLocationServlet(RestServlet):
 
     @defer.inlineCallbacks
     def on_GET(self, request, protocol):
-        yield self.auth.get_user_by_req(request)
+        yield self.auth.get_user_by_req(request, allow_guest=True)
 
         fields = request.args
         fields.pop("access_token", None)
diff --git a/synapse/types.py b/synapse/types.py
index 9666f9d73f..c87ed813b9 100644
--- a/synapse/types.py
+++ b/synapse/types.py
@@ -216,9 +216,7 @@ class StreamToken(
             return self
 
     def copy_and_replace(self, key, new_value):
-        d = self._asdict()
-        d[key] = new_value
-        return StreamToken(**d)
+        return self._replace(**{key: new_value})
 
 
 StreamToken.START = StreamToken(
diff --git a/synapse/util/async.py b/synapse/util/async.py
index 35380bf8ed..1453faf0ef 100644
--- a/synapse/util/async.py
+++ b/synapse/util/async.py
@@ -89,6 +89,11 @@ class ObservableDeferred(object):
         deferred.addCallbacks(callback, errback)
 
     def observe(self):
+        """Observe the underlying deferred.
+
+        Can return either a deferred if the underlying deferred is still pending
+        (or has failed), or the actual value. Callers may need to use maybeDeferred.
+        """
         if not self._result:
             d = defer.Deferred()
 
@@ -101,7 +106,7 @@ class ObservableDeferred(object):
             return d
         else:
             success, res = self._result
-            return defer.succeed(res) if success else defer.fail(res)
+            return res if success else defer.fail(res)
 
     def observers(self):
         return self._observers
diff --git a/synapse/util/caches/descriptors.py b/synapse/util/caches/descriptors.py
index 19595df422..9d0d0be1f9 100644
--- a/synapse/util/caches/descriptors.py
+++ b/synapse/util/caches/descriptors.py
@@ -15,12 +15,9 @@
 import logging
 
 from synapse.util.async import ObservableDeferred
-from synapse.util import unwrapFirstError
+from synapse.util import unwrapFirstError, logcontext
 from synapse.util.caches.lrucache import LruCache
 from synapse.util.caches.treecache import TreeCache, iterate_tree_cache_entry
-from synapse.util.logcontext import (
-    PreserveLoggingContext, preserve_context_over_deferred, preserve_context_over_fn
-)
 
 from . import DEBUG_CACHES, register_cache
 
@@ -227,8 +224,20 @@ class _CacheDescriptorBase(object):
             )
 
         self.num_args = num_args
+
+        # list of the names of the args used as the cache key
         self.arg_names = all_args[1:num_args + 1]
 
+        # self.arg_defaults is a map of arg name to its default value for each
+        # argument that has a default value
+        if arg_spec.defaults:
+            self.arg_defaults = dict(zip(
+                all_args[-len(arg_spec.defaults):],
+                arg_spec.defaults
+            ))
+        else:
+            self.arg_defaults = {}
+
         if "cache_context" in self.arg_names:
             raise Exception(
                 "cache_context arg cannot be included among the cache keys"
@@ -292,18 +301,31 @@ class CacheDescriptor(_CacheDescriptorBase):
             iterable=self.iterable,
         )
 
+        def get_cache_key(args, kwargs):
+            """Given some args/kwargs return a generator that resolves into
+            the cache_key.
+
+            We loop through each arg name, looking up if its in the `kwargs`,
+            otherwise using the next argument in `args`. If there are no more
+            args then we try looking the arg name up in the defaults
+            """
+            pos = 0
+            for nm in self.arg_names:
+                if nm in kwargs:
+                    yield kwargs[nm]
+                elif pos < len(args):
+                    yield args[pos]
+                    pos += 1
+                else:
+                    yield self.arg_defaults[nm]
+
         @functools.wraps(self.orig)
         def wrapped(*args, **kwargs):
             # If we're passed a cache_context then we'll want to call its invalidate()
             # whenever we are invalidated
             invalidate_callback = kwargs.pop("on_invalidate", None)
 
-            # Add temp cache_context so inspect.getcallargs doesn't explode
-            if self.add_cache_context:
-                kwargs["cache_context"] = None
-
-            arg_dict = inspect.getcallargs(self.orig, obj, *args, **kwargs)
-            cache_key = tuple(arg_dict[arg_nm] for arg_nm in self.arg_names)
+            cache_key = tuple(get_cache_key(args, kwargs))
 
             # Add our own `cache_context` to argument list if the wrapped function
             # has asked for one
@@ -328,11 +350,9 @@ class CacheDescriptor(_CacheDescriptorBase):
                         defer.returnValue(cached_result)
                     observer.addCallback(check_result)
 
-                return preserve_context_over_deferred(observer)
             except KeyError:
                 ret = defer.maybeDeferred(
-                    preserve_context_over_fn,
-                    self.function_to_call,
+                    logcontext.preserve_fn(self.function_to_call),
                     obj, *args, **kwargs
                 )
 
@@ -342,10 +362,14 @@ class CacheDescriptor(_CacheDescriptorBase):
 
                 ret.addErrback(onErr)
 
-                ret = ObservableDeferred(ret, consumeErrors=True)
-                cache.set(cache_key, ret, callback=invalidate_callback)
+                result_d = ObservableDeferred(ret, consumeErrors=True)
+                cache.set(cache_key, result_d, callback=invalidate_callback)
+                observer = result_d.observe()
 
-                return preserve_context_over_deferred(ret.observe())
+            if isinstance(observer, defer.Deferred):
+                return logcontext.make_deferred_yieldable(observer)
+            else:
+                return observer
 
         wrapped.invalidate = cache.invalidate
         wrapped.invalidate_all = cache.invalidate_all
@@ -362,7 +386,11 @@ class CacheListDescriptor(_CacheDescriptorBase):
     """Wraps an existing cache to support bulk fetching of keys.
 
     Given a list of keys it looks in the cache to find any hits, then passes
-    the list of missing keys to the wrapped fucntion.
+    the list of missing keys to the wrapped function.
+
+    Once wrapped, the function returns either a Deferred which resolves to
+    the list of results, or (if all results were cached), just the list of
+    results.
     """
 
     def __init__(self, orig, cached_method_name, list_name, num_args=None,
@@ -433,8 +461,7 @@ class CacheListDescriptor(_CacheDescriptorBase):
                 args_to_call[self.list_name] = missing
 
                 ret_d = defer.maybeDeferred(
-                    preserve_context_over_fn,
-                    self.function_to_call,
+                    logcontext.preserve_fn(self.function_to_call),
                     **args_to_call
                 )
 
@@ -443,8 +470,7 @@ class CacheListDescriptor(_CacheDescriptorBase):
                 # We need to create deferreds for each arg in the list so that
                 # we can insert the new deferred into the cache.
                 for arg in missing:
-                    with PreserveLoggingContext():
-                        observer = ret_d.observe()
+                    observer = ret_d.observe()
                     observer.addCallback(lambda r, arg: r.get(arg, None), arg)
 
                     observer = ObservableDeferred(observer)
@@ -471,7 +497,7 @@ class CacheListDescriptor(_CacheDescriptorBase):
                     results.update(res)
                     return results
 
-                return preserve_context_over_deferred(defer.gatherResults(
+                return logcontext.make_deferred_yieldable(defer.gatherResults(
                     cached_defers.values(),
                     consumeErrors=True,
                 ).addCallback(update_results_dict).addErrback(
diff --git a/synapse/util/logcontext.py b/synapse/util/logcontext.py
index ff67b1d794..990216145e 100644
--- a/synapse/util/logcontext.py
+++ b/synapse/util/logcontext.py
@@ -310,6 +310,10 @@ def preserve_context_over_fn(fn, *args, **kwargs):
 def preserve_context_over_deferred(deferred, context=None):
     """Given a deferred wrap it such that any callbacks added later to it will
     be invoked with the current context.
+
+    Deprecated: this almost certainly doesn't do want you want, ie make
+    the deferred follow the synapse logcontext rules: try
+    ``make_deferred_yieldable`` instead.
     """
     if context is None:
         context = LoggingContext.current_context()
@@ -330,12 +334,8 @@ def preserve_fn(f):
         LoggingContext.set_current_context(LoggingContext.sentinel)
         return result
 
-    # XXX: why is this here rather than inside g? surely we want to preserve
-    # the context from the time the function was called, not when it was
-    # wrapped?
-    current = LoggingContext.current_context()
-
     def g(*args, **kwargs):
+        current = LoggingContext.current_context()
         res = f(*args, **kwargs)
         if isinstance(res, defer.Deferred) and not res.called:
             # The function will have reset the context before returning, so
@@ -359,6 +359,25 @@ def preserve_fn(f):
     return g
 
 
+@defer.inlineCallbacks
+def make_deferred_yieldable(deferred):
+    """Given a deferred, make it follow the Synapse logcontext rules:
+
+    If the deferred has completed (or is not actually a Deferred), essentially
+    does nothing (just returns another completed deferred with the
+    result/failure).
+
+    If the deferred has not yet completed, resets the logcontext before
+    returning a deferred. Then, when the deferred completes, restores the
+    current logcontext before running callbacks/errbacks.
+
+    (This is more-or-less the opposite operation to preserve_fn.)
+    """
+    with PreserveLoggingContext():
+        r = yield deferred
+    defer.returnValue(r)
+
+
 # modules to ignore in `logcontext_tracer`
 _to_ignore = [
     "synapse.util.logcontext",
diff --git a/synapse/visibility.py b/synapse/visibility.py
index 31659156ae..c4dd9ae2c7 100644
--- a/synapse/visibility.py
+++ b/synapse/visibility.py
@@ -56,7 +56,8 @@ def filter_events_for_clients(store, user_tuples, events, event_id_to_state):
         events ([synapse.events.EventBase]): list of events to filter
     """
     forgotten = yield preserve_context_over_deferred(defer.gatherResults([
-        preserve_fn(store.who_forgot_in_room)(
+        defer.maybeDeferred(
+            preserve_fn(store.who_forgot_in_room),
             room_id,
         )
         for room_id in frozenset(e.room_id for e in events)
diff --git a/tests/appservice/test_appservice.py b/tests/appservice/test_appservice.py
index aa8cc50550..7586ea9053 100644
--- a/tests/appservice/test_appservice.py
+++ b/tests/appservice/test_appservice.py
@@ -19,10 +19,12 @@ from twisted.internet import defer
 from mock import Mock
 from tests import unittest
 
+import re
+
 
 def _regex(regex, exclusive=True):
     return {
-        "regex": regex,
+        "regex": re.compile(regex),
         "exclusive": exclusive
     }
 
diff --git a/tests/storage/test__base.py b/tests/storage/test__base.py
index 8361dd8cee..281eb16254 100644
--- a/tests/storage/test__base.py
+++ b/tests/storage/test__base.py
@@ -199,7 +199,7 @@ class CacheDecoratorTestCase(unittest.TestCase):
 
         a.func.prefill(("foo",), ObservableDeferred(d))
 
-        self.assertEquals(a.func("foo").result, d.result)
+        self.assertEquals(a.func("foo"), d.result)
         self.assertEquals(callcount[0], 0)
 
     @defer.inlineCallbacks
diff --git a/tests/util/caches/test_descriptors.py b/tests/util/caches/test_descriptors.py
index 419281054d..3f14ab503f 100644
--- a/tests/util/caches/test_descriptors.py
+++ b/tests/util/caches/test_descriptors.py
@@ -12,11 +12,18 @@
 # 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 mock
+from synapse.api.errors import SynapseError
+from synapse.util import async
+from synapse.util import logcontext
 from twisted.internet import defer
 from synapse.util.caches import descriptors
 from tests import unittest
 
+logger = logging.getLogger(__name__)
+
 
 class DescriptorTestCase(unittest.TestCase):
     @defer.inlineCallbacks
@@ -84,3 +91,125 @@ class DescriptorTestCase(unittest.TestCase):
         r = yield obj.fn(2, 5)
         self.assertEqual(r, 'chips')
         obj.mock.assert_not_called()
+
+    def test_cache_logcontexts(self):
+        """Check that logcontexts are set and restored correctly when
+        using the cache."""
+
+        complete_lookup = defer.Deferred()
+
+        class Cls(object):
+            @descriptors.cached()
+            def fn(self, arg1):
+                @defer.inlineCallbacks
+                def inner_fn():
+                    with logcontext.PreserveLoggingContext():
+                        yield complete_lookup
+                    defer.returnValue(1)
+
+                return inner_fn()
+
+        @defer.inlineCallbacks
+        def do_lookup():
+            with logcontext.LoggingContext() as c1:
+                c1.name = "c1"
+                r = yield obj.fn(1)
+                self.assertEqual(logcontext.LoggingContext.current_context(),
+                                 c1)
+            defer.returnValue(r)
+
+        def check_result(r):
+            self.assertEqual(r, 1)
+
+        obj = Cls()
+
+        # set off a deferred which will do a cache lookup
+        d1 = do_lookup()
+        self.assertEqual(logcontext.LoggingContext.current_context(),
+                         logcontext.LoggingContext.sentinel)
+        d1.addCallback(check_result)
+
+        # and another
+        d2 = do_lookup()
+        self.assertEqual(logcontext.LoggingContext.current_context(),
+                         logcontext.LoggingContext.sentinel)
+        d2.addCallback(check_result)
+
+        # let the lookup complete
+        complete_lookup.callback(None)
+
+        return defer.gatherResults([d1, d2])
+
+    def test_cache_logcontexts_with_exception(self):
+        """Check that the cache sets and restores logcontexts correctly when
+        the lookup function throws an exception"""
+
+        class Cls(object):
+            @descriptors.cached()
+            def fn(self, arg1):
+                @defer.inlineCallbacks
+                def inner_fn():
+                    yield async.run_on_reactor()
+                    raise SynapseError(400, "blah")
+
+                return inner_fn()
+
+        @defer.inlineCallbacks
+        def do_lookup():
+            with logcontext.LoggingContext() as c1:
+                c1.name = "c1"
+                try:
+                    yield obj.fn(1)
+                    self.fail("No exception thrown")
+                except SynapseError:
+                    pass
+
+                self.assertEqual(logcontext.LoggingContext.current_context(),
+                                 c1)
+
+        obj = Cls()
+
+        # set off a deferred which will do a cache lookup
+        d1 = do_lookup()
+        self.assertEqual(logcontext.LoggingContext.current_context(),
+                         logcontext.LoggingContext.sentinel)
+
+        return d1
+
+    @defer.inlineCallbacks
+    def test_cache_default_args(self):
+        class Cls(object):
+            def __init__(self):
+                self.mock = mock.Mock()
+
+            @descriptors.cached()
+            def fn(self, arg1, arg2=2, arg3=3):
+                return self.mock(arg1, arg2, arg3)
+
+        obj = Cls()
+
+        obj.mock.return_value = 'fish'
+        r = yield obj.fn(1, 2, 3)
+        self.assertEqual(r, 'fish')
+        obj.mock.assert_called_once_with(1, 2, 3)
+        obj.mock.reset_mock()
+
+        # a call with same params shouldn't call the mock again
+        r = yield obj.fn(1, 2)
+        self.assertEqual(r, 'fish')
+        obj.mock.assert_not_called()
+        obj.mock.reset_mock()
+
+        # a call with different params should call the mock again
+        obj.mock.return_value = 'chips'
+        r = yield obj.fn(2, 3)
+        self.assertEqual(r, 'chips')
+        obj.mock.assert_called_once_with(2, 3, 3)
+        obj.mock.reset_mock()
+
+        # the two values should now be cached
+        r = yield obj.fn(1, 2)
+        self.assertEqual(r, 'fish')
+        r = yield obj.fn(2, 3)
+        self.assertEqual(r, 'chips')
+        obj.mock.assert_not_called()
diff --git a/tests/util/test_snapshot_cache.py b/tests/util/test_snapshot_cache.py
index 7e289715ba..d3a8630c2f 100644
--- a/tests/util/test_snapshot_cache.py
+++ b/tests/util/test_snapshot_cache.py
@@ -53,7 +53,9 @@ class SnapshotCacheTestCase(unittest.TestCase):
         # before the cache expires returns a resolved deferred.
         get_result_at_11 = self.cache.get(11, "key")
         self.assertIsNotNone(get_result_at_11)
-        self.assertTrue(get_result_at_11.called)
+        if isinstance(get_result_at_11, Deferred):
+            # The cache may return the actual result rather than a deferred
+            self.assertTrue(get_result_at_11.called)
 
         # Check that getting the key after the deferred has resolved
         # after the cache expires returns None