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-rw-r--r--docs/log_contexts.rst11
-rw-r--r--synapse/appservice/__init__.py38
-rw-r--r--synapse/handlers/initial_sync.py1
-rw-r--r--synapse/handlers/presence.py3
-rw-r--r--synapse/handlers/room_list.py2
-rw-r--r--synapse/handlers/sync.py2
-rw-r--r--synapse/push/emailpusher.py2
-rw-r--r--synapse/push/push_rule_evaluator.py104
-rw-r--r--synapse/push/push_tools.py7
-rw-r--r--synapse/rest/client/v1/room.py1
-rw-r--r--synapse/storage/event_push_actions.py9
-rw-r--r--synapse/storage/events.py1
-rw-r--r--synapse/storage/search.py2
-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.py23
-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
22 files changed, 318 insertions, 111 deletions
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/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/handlers/initial_sync.py b/synapse/handlers/initial_sync.py
index 10f5f35a69..2a81c11f10 100644
--- a/synapse/handlers/initial_sync.py
+++ b/synapse/handlers/initial_sync.py
@@ -372,6 +372,7 @@ class InitialSyncHandler(BaseHandler):
 
         @defer.inlineCallbacks
         def get_presence():
+            defer.returnValue([])
             states = yield presence_handler.get_states(
                 [m.user_id for m in room_members],
                 as_event=True,
diff --git a/synapse/handlers/presence.py b/synapse/handlers/presence.py
index ac6d1107bf..7f6365ae1b 100644
--- a/synapse/handlers/presence.py
+++ b/synapse/handlers/presence.py
@@ -376,6 +376,7 @@ class PresenceHandler(object):
         """We've seen the user do something that indicates they're interacting
         with the app.
         """
+        return
         user_id = user.to_string()
 
         bump_active_time_counter.inc()
@@ -405,6 +406,7 @@ class PresenceHandler(object):
                 Useful for streams that are not associated with an actual
                 client that is being used by a user.
         """
+        affect_presence = False
         if affect_presence:
             curr_sync = self.user_to_num_current_syncs.get(user_id, 0)
             self.user_to_num_current_syncs[user_id] = curr_sync + 1
@@ -466,6 +468,7 @@ class PresenceHandler(object):
             syncing_user_ids(set(str)): The set of user_ids that are
                 currently syncing on that server.
         """
+        return
 
         # Grab the previous list of user_ids that were syncing on that process
         prev_syncing_user_ids = (
diff --git a/synapse/handlers/room_list.py b/synapse/handlers/room_list.py
index 516cd9a6ac..31ae4613c1 100644
--- a/synapse/handlers/room_list.py
+++ b/synapse/handlers/room_list.py
@@ -43,7 +43,7 @@ EMTPY_THIRD_PARTY_ID = ThirdPartyInstanceID(None, None)
 class RoomListHandler(BaseHandler):
     def __init__(self, hs):
         super(RoomListHandler, self).__init__(hs)
-        self.response_cache = ResponseCache(hs)
+        self.response_cache = ResponseCache(hs, timeout_ms=10 * 60 * 1000)
         self.remote_response_cache = ResponseCache(hs, timeout_ms=30 * 1000)
 
     def get_local_public_room_list(self, limit=None, since_token=None,
diff --git a/synapse/handlers/sync.py b/synapse/handlers/sync.py
index c0205da1a9..a1264925af 100644
--- a/synapse/handlers/sync.py
+++ b/synapse/handlers/sync.py
@@ -539,7 +539,7 @@ class SyncHandler(object):
             since_token is None and
             sync_config.filter_collection.blocks_all_presence()
         )
-        if not block_all_presence_data:
+        if False or not block_all_presence_data:
             yield self._generate_sync_entry_for_presence(
                 sync_result_builder, newly_joined_rooms, newly_joined_users
             )
diff --git a/synapse/push/emailpusher.py b/synapse/push/emailpusher.py
index c7afd11111..b3e0098a86 100644
--- a/synapse/push/emailpusher.py
+++ b/synapse/push/emailpusher.py
@@ -219,7 +219,7 @@ class EmailPusher(object):
 
     def seconds_until(self, ts_msec):
         secs = (ts_msec - self.clock.time_msec()) / 1000
-        return max(secs, 0)
+        return max(secs, 0)  # Ensure non-negative
 
     def get_room_throttle_ms(self, room_id):
         if room_id in self.throttle_params:
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/room.py b/synapse/rest/client/v1/room.py
index 0bdd6b5b36..ee69b43b2e 100644
--- a/synapse/rest/client/v1/room.py
+++ b/synapse/rest/client/v1/room.py
@@ -474,6 +474,7 @@ class RoomInitialSyncRestServlet(ClientV1RestServlet):
 
     @defer.inlineCallbacks
     def on_GET(self, request, room_id):
+        # raise RuntimeError("Guest access has been disabled")
         requester = yield self.auth.get_user_by_req(request, allow_guest=True)
         pagination_config = PaginationConfig.from_request(request)
         content = yield self.initial_sync_handler.room_initial_sync(
diff --git a/synapse/storage/event_push_actions.py b/synapse/storage/event_push_actions.py
index d6d8723b4a..c9db3297ab 100644
--- a/synapse/storage/event_push_actions.py
+++ b/synapse/storage/event_push_actions.py
@@ -87,6 +87,8 @@ class EventPushActionsStore(SQLBaseStore):
         self._rotate_notif_loop = self._clock.looping_call(
             self._rotate_notifs, 30 * 60 * 1000
         )
+        self._rotate_delay = 3
+        self._rotate_count = 10000
 
     def _set_push_actions_for_event_and_users_txn(self, txn, event, tuples):
         """
@@ -629,7 +631,7 @@ class EventPushActionsStore(SQLBaseStore):
                 )
                 if caught_up:
                     break
-                yield sleep(5)
+                yield sleep(self._rotate_delay)
         finally:
             self._doing_notif_rotation = False
 
@@ -650,9 +652,10 @@ class EventPushActionsStore(SQLBaseStore):
         txn.execute("""
             SELECT stream_ordering FROM event_push_actions
             WHERE stream_ordering > ?
-            ORDER BY stream_ordering ASC LIMIT 1 OFFSET 50000
-        """, (old_rotate_stream_ordering,))
+            ORDER BY stream_ordering ASC LIMIT 1 OFFSET ?
+        """, (old_rotate_stream_ordering, self._rotate_count))
         stream_row = txn.fetchone()
+        # stream_row = (old_rotate_stream_ordering + self._rotate_count,)
         if stream_row:
             offset_stream_ordering, = stream_row
             rotate_to_stream_ordering = min(
diff --git a/synapse/storage/events.py b/synapse/storage/events.py
index 64fe937bdc..66db7c44b9 100644
--- a/synapse/storage/events.py
+++ b/synapse/storage/events.py
@@ -939,7 +939,6 @@ class EventsStore(SQLBaseStore):
                 "event_edge_hashes",
                 "event_edges",
                 "event_forward_extremities",
-                "event_push_actions",
                 "event_reference_hashes",
                 "event_search",
                 "event_signatures",
diff --git a/synapse/storage/search.py b/synapse/storage/search.py
index 8f2b3c4435..17c6c55714 100644
--- a/synapse/storage/search.py
+++ b/synapse/storage/search.py
@@ -600,7 +600,7 @@ def _parse_query(database_engine, search_term):
     results = re.findall(r"([\w\-]+)", search_term, re.UNICODE)
 
     if isinstance(database_engine, PostgresEngine):
-        return " & ".join(result + ":*" for result in results)
+        return " & ".join(result for result in results)
     elif isinstance(database_engine, Sqlite3Engine):
         return " & ".join(result + "*" for result in results)
     else:
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..857afee7cb 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()
@@ -359,6 +363,25 @@ 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