Merge branch 'release-v0.18.4' of github.com:matrix-org/synapse v0.18.4

32 files changed, 383 insertions, 430 deletions

diff --git a/CHANGES.rst b/CHANGES.rst
index 1ce58632b8..a1a0624674 100644
--- a/CHANGES.rst
+++ b/CHANGES.rst
@@ -1,3 +1,31 @@
+Changes in synapse v0.18.4 (2016-11-22)
+=======================================
+
+Bug fixes:
+
+* Add workaround for buggy clients that the fail to register (PR #1632)
+
+
+Changes in synapse v0.18.4-rc1 (2016-11-14)
+===========================================
+
+Changes:
+
+* Various database efficiency improvements (PR #1188, #1192)
+* Update default config to blacklist more internal IPs, thanks to Euan Kemp (PR
+  #1198)
+* Allow specifying duration in minutes in config, thanks to Daniel Dent (PR
+  #1625)
+
+
+Bug fixes:
+
+* Fix media repo to set CORs headers on responses (PR #1190)
+* Fix registration to not error on non-ascii passwords (PR #1191)
+* Fix create event code to limit the number of prev_events (PR #1615)
+* Fix bug in transaction ID deduplication (PR #1624)
+
+
 Changes in synapse v0.18.3 (2016-11-08)
 =======================================
 
diff --git a/docs/metrics-howto.rst b/docs/metrics-howto.rst
index 7aa4757a35..ca10799b00 100644
--- a/docs/metrics-howto.rst
+++ b/docs/metrics-howto.rst
@@ -51,9 +51,9 @@ python_gc_counts            reactor_gc_counts
 
 The twisted-specific reactor metrics have been renamed.
 
-==================================== =================
+==================================== =====================
 New name                             Old name
------------------------------------- -----------------
-python_twisted_reactor_pending_calls reactor_tick_time
+------------------------------------ ---------------------
+python_twisted_reactor_pending_calls reactor_pending_calls
 python_twisted_reactor_tick_time     reactor_tick_time
-==================================== =================
+==================================== =====================
diff --git a/synapse/__init__.py b/synapse/__init__.py
index d366b69dab..432567a110 100644
--- a/synapse/__init__.py
+++ b/synapse/__init__.py
@@ -16,4 +16,4 @@
 """ This is a reference implementation of a Matrix home server.
 """
 
-__version__ = "0.18.3"
+__version__ = "0.18.4"
diff --git a/synapse/app/appservice.py b/synapse/app/appservice.py
index 4e62a84b28..dd9ee406a1 100644
--- a/synapse/app/appservice.py
+++ b/synapse/app/appservice.py
@@ -34,6 +34,8 @@ from synapse.util.manhole import manhole
 from synapse.util.rlimit import change_resource_limit
 from synapse.util.versionstring import get_version_string
 
+from synapse import events
+
 from twisted.internet import reactor, defer
 from twisted.web.resource import Resource
 
@@ -151,6 +153,8 @@ def start(config_options):
 
     setup_logging(config.worker_log_config, config.worker_log_file)
 
+    events.USE_FROZEN_DICTS = config.use_frozen_dicts
+
     database_engine = create_engine(config.database_config)
 
     if config.notify_appservices:
diff --git a/synapse/app/client_reader.py b/synapse/app/client_reader.py
index 9fccc73db3..0086a2977e 100644
--- a/synapse/app/client_reader.py
+++ b/synapse/app/client_reader.py
@@ -41,6 +41,8 @@ from synapse.util.rlimit import change_resource_limit
 from synapse.util.versionstring import get_version_string
 from synapse.crypto import context_factory
 
+from synapse import events
+
 
 from twisted.internet import reactor, defer
 from twisted.web.resource import Resource
@@ -165,6 +167,8 @@ def start(config_options):
 
     setup_logging(config.worker_log_config, config.worker_log_file)
 
+    events.USE_FROZEN_DICTS = config.use_frozen_dicts
+
     database_engine = create_engine(config.database_config)
 
     tls_server_context_factory = context_factory.ServerContextFactory(config)
diff --git a/synapse/app/federation_reader.py b/synapse/app/federation_reader.py
index 1f5ae1937e..b5f59a9931 100644
--- a/synapse/app/federation_reader.py
+++ b/synapse/app/federation_reader.py
@@ -39,6 +39,8 @@ from synapse.api.urls import FEDERATION_PREFIX
 from synapse.federation.transport.server import TransportLayerServer
 from synapse.crypto import context_factory
 
+from synapse import events
+
 
 from twisted.internet import reactor, defer
 from twisted.web.resource import Resource
@@ -156,6 +158,8 @@ def start(config_options):
 
     setup_logging(config.worker_log_config, config.worker_log_file)
 
+    events.USE_FROZEN_DICTS = config.use_frozen_dicts
+
     database_engine = create_engine(config.database_config)
 
     tls_server_context_factory = context_factory.ServerContextFactory(config)
diff --git a/synapse/app/media_repository.py b/synapse/app/media_repository.py
index 6e5ec01c6c..44c19a1bef 100644
--- a/synapse/app/media_repository.py
+++ b/synapse/app/media_repository.py
@@ -41,6 +41,8 @@ from synapse.api.urls import (
 )
 from synapse.crypto import context_factory
 
+from synapse import events
+
 
 from twisted.internet import reactor, defer
 from twisted.web.resource import Resource
@@ -162,6 +164,8 @@ def start(config_options):
 
     setup_logging(config.worker_log_config, config.worker_log_file)
 
+    events.USE_FROZEN_DICTS = config.use_frozen_dicts
+
     database_engine = create_engine(config.database_config)
 
     tls_server_context_factory = context_factory.ServerContextFactory(config)
diff --git a/synapse/app/pusher.py b/synapse/app/pusher.py
index 1a6f5507a9..a0e765c54f 100644
--- a/synapse/app/pusher.py
+++ b/synapse/app/pusher.py
@@ -36,6 +36,8 @@ from synapse.util.manhole import manhole
 from synapse.util.rlimit import change_resource_limit
 from synapse.util.versionstring import get_version_string
 
+from synapse import events
+
 from twisted.internet import reactor, defer
 from twisted.web.resource import Resource
 
@@ -239,6 +241,8 @@ def start(config_options):
 
     setup_logging(config.worker_log_config, config.worker_log_file)
 
+    events.USE_FROZEN_DICTS = config.use_frozen_dicts
+
     if config.start_pushers:
         sys.stderr.write(
             "\nThe pushers must be disabled in the main synapse process"
diff --git a/synapse/app/synchrotron.py b/synapse/app/synchrotron.py
index 64b209ffe6..bf1b995dc2 100644
--- a/synapse/app/synchrotron.py
+++ b/synapse/app/synchrotron.py
@@ -446,6 +446,8 @@ def start(config_options):
 
     setup_logging(config.worker_log_config, config.worker_log_file)
 
+    synapse.events.USE_FROZEN_DICTS = config.use_frozen_dicts
+
     database_engine = create_engine(config.database_config)
 
     ss = SynchrotronServer(
diff --git a/synapse/config/_base.py b/synapse/config/_base.py
index af9f17bf7b..1ab5593c6e 100644
--- a/synapse/config/_base.py
+++ b/synapse/config/_base.py
@@ -64,11 +64,12 @@ class Config(object):
         if isinstance(value, int) or isinstance(value, long):
             return value
         second = 1000
-        hour = 60 * 60 * second
+        minute = 60 * second
+        hour = 60 * minute
         day = 24 * hour
         week = 7 * day
         year = 365 * day
-        sizes = {"s": second, "h": hour, "d": day, "w": week, "y": year}
+        sizes = {"s": second, "m": minute, "h": hour, "d": day, "w": week, "y": year}
         size = 1
         suffix = value[-1]
         if suffix in sizes:
diff --git a/synapse/config/password_auth_providers.py b/synapse/config/password_auth_providers.py
index f6d9bb1c62..1f438d2bb3 100644
--- a/synapse/config/password_auth_providers.py
+++ b/synapse/config/password_auth_providers.py
@@ -13,7 +13,7 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
-from ._base import Config
+from ._base import Config, ConfigError
 
 import importlib
 
@@ -39,7 +39,12 @@ class PasswordAuthProviderConfig(Config):
             module = importlib.import_module(module)
             provider_class = getattr(module, clz)
 
-            provider_config = provider_class.parse_config(provider["config"])
+            try:
+                provider_config = provider_class.parse_config(provider["config"])
+            except Exception as e:
+                raise ConfigError(
+                    "Failed to parse config for %r: %r" % (provider['module'], e)
+                )
             self.password_providers.append((provider_class, provider_config))
 
     def default_config(self, **kwargs):
diff --git a/synapse/config/repository.py b/synapse/config/repository.py
index 8810079848..2c6f57168e 100644
--- a/synapse/config/repository.py
+++ b/synapse/config/repository.py
@@ -167,6 +167,8 @@ class ContentRepositoryConfig(Config):
         # - '10.0.0.0/8'
         # - '172.16.0.0/12'
         # - '192.168.0.0/16'
+        # - '100.64.0.0/10'
+        # - '169.254.0.0/16'
         #
         # List of IP address CIDR ranges that the URL preview spider is allowed
         # to access even if they are specified in url_preview_ip_range_blacklist.
diff --git a/synapse/handlers/auth.py b/synapse/handlers/auth.py
index 3635521230..3851b35889 100644
--- a/synapse/handlers/auth.py
+++ b/synapse/handlers/auth.py
@@ -653,7 +653,7 @@ class AuthHandler(BaseHandler):
         Returns:
             Hashed password (str).
         """
-        return bcrypt.hashpw(password + self.hs.config.password_pepper,
+        return bcrypt.hashpw(password.encode('utf8') + self.hs.config.password_pepper,
                              bcrypt.gensalt(self.bcrypt_rounds))
 
     def validate_hash(self, password, stored_hash):
diff --git a/synapse/handlers/message.py b/synapse/handlers/message.py
index abfa8c65a4..81df45177a 100644
--- a/synapse/handlers/message.py
+++ b/synapse/handlers/message.py
@@ -34,6 +34,7 @@ from ._base import BaseHandler
 from canonicaljson import encode_canonical_json
 
 import logging
+import random
 
 logger = logging.getLogger(__name__)
 
@@ -415,6 +416,20 @@ class MessageHandler(BaseHandler):
                 builder.room_id,
             )
 
+            # We want to limit the max number of prev events we point to in our
+            # new event
+            if len(latest_ret) > 10:
+                # Sort by reverse depth, so we point to the most recent.
+                latest_ret.sort(key=lambda a: -a[2])
+                new_latest_ret = latest_ret[:5]
+
+                # We also randomly point to some of the older events, to make
+                # sure that we don't completely ignore the older events.
+                if latest_ret[5:]:
+                    sample_size = min(5, len(latest_ret[5:]))
+                    new_latest_ret.extend(random.sample(latest_ret[5:], sample_size))
+                latest_ret = new_latest_ret
+
             if latest_ret:
                 depth = max([d for _, _, d in latest_ret]) + 1
             else:
diff --git a/synapse/http/server.py b/synapse/http/server.py
index 168e53ce0c..14715878c5 100644
--- a/synapse/http/server.py
+++ b/synapse/http/server.py
@@ -392,17 +392,30 @@ def respond_with_json_bytes(request, code, json_bytes, send_cors=False,
     request.setHeader(b"Content-Length", b"%d" % (len(json_bytes),))
 
     if send_cors:
-        request.setHeader("Access-Control-Allow-Origin", "*")
-        request.setHeader("Access-Control-Allow-Methods",
-                          "GET, POST, PUT, DELETE, OPTIONS")
-        request.setHeader("Access-Control-Allow-Headers",
-                          "Origin, X-Requested-With, Content-Type, Accept")
+        set_cors_headers(request)
 
     request.write(json_bytes)
     finish_request(request)
     return NOT_DONE_YET
 
 
+def set_cors_headers(request):
+    """Set the CORs headers so that javascript running in a web browsers can
+    use this API
+
+    Args:
+        request (twisted.web.http.Request): The http request to add CORs to.
+    """
+    request.setHeader("Access-Control-Allow-Origin", "*")
+    request.setHeader(
+        "Access-Control-Allow-Methods", "GET, POST, PUT, DELETE, OPTIONS"
+    )
+    request.setHeader(
+        "Access-Control-Allow-Headers",
+        "Origin, X-Requested-With, Content-Type, Accept"
+    )
+
+
 def finish_request(request):
     """ Finish writing the response to the request.
 
diff --git a/synapse/metrics/__init__.py b/synapse/metrics/__init__.py
index 7041da25ce..2265e6e8d6 100644
--- a/synapse/metrics/__init__.py
+++ b/synapse/metrics/__init__.py
@@ -111,18 +111,20 @@ def render_all():
     return "\n".join(strs)
 
 
-reactor_metrics = get_metrics_for("reactor")
-tick_time = reactor_metrics.register_distribution("tick_time")
-pending_calls_metric = reactor_metrics.register_distribution("pending_calls")
+register_process_collector(get_metrics_for("process"))
+
 
-gc_time = reactor_metrics.register_distribution("gc_time", labels=["gen"])
-gc_unreachable = reactor_metrics.register_counter("gc_unreachable", labels=["gen"])
+python_metrics = get_metrics_for("python")
 
-reactor_metrics.register_callback(
+gc_time = python_metrics.register_distribution("gc_time", labels=["gen"])
+gc_unreachable = python_metrics.register_counter("gc_unreachable_total", labels=["gen"])
+python_metrics.register_callback(
     "gc_counts", lambda: {(i,): v for i, v in enumerate(gc.get_count())}, labels=["gen"]
 )
 
-register_process_collector(get_metrics_for("process"))
+reactor_metrics = get_metrics_for("python.twisted.reactor")
+tick_time = reactor_metrics.register_distribution("tick_time")
+pending_calls_metric = reactor_metrics.register_distribution("pending_calls")
 
 
 def runUntilCurrentTimer(func):
diff --git a/synapse/metrics/process_collector.py b/synapse/metrics/process_collector.py
index 0e95582368..6fec3de399 100644
--- a/synapse/metrics/process_collector.py
+++ b/synapse/metrics/process_collector.py
@@ -13,12 +13,7 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
-# Because otherwise 'resource' collides with synapse.metrics.resource
-from __future__ import absolute_import
-
 import os
-import stat
-from resource import getrusage, RUSAGE_SELF
 
 
 TICKS_PER_SEC = 100
@@ -29,16 +24,6 @@ HAVE_PROC_SELF_STAT = os.path.exists("/proc/self/stat")
 HAVE_PROC_SELF_LIMITS = os.path.exists("/proc/self/limits")
 HAVE_PROC_SELF_FD = os.path.exists("/proc/self/fd")
 
-TYPES = {
-    stat.S_IFSOCK: "SOCK",
-    stat.S_IFLNK: "LNK",
-    stat.S_IFREG: "REG",
-    stat.S_IFBLK: "BLK",
-    stat.S_IFDIR: "DIR",
-    stat.S_IFCHR: "CHR",
-    stat.S_IFIFO: "FIFO",
-}
-
 # Field indexes from /proc/self/stat, taken from the proc(5) manpage
 STAT_FIELDS = {
     "utime": 14,
@@ -49,9 +34,7 @@ STAT_FIELDS = {
 }
 
 
-rusage = None
 stats = {}
-fd_counts = None
 
 # In order to report process_start_time_seconds we need to know the
 # machine's boot time, because the value in /proc/self/stat is relative to
@@ -65,9 +48,6 @@ if HAVE_PROC_STAT:
 
 
 def update_resource_metrics():
-    global rusage
-    rusage = getrusage(RUSAGE_SELF)
-
     if HAVE_PROC_SELF_STAT:
         global stats
         with open("/proc/self/stat") as s:
@@ -80,52 +60,17 @@ def update_resource_metrics():
                 # we've lost the first two fields in PID and COMMAND above
                 stats[name] = int(raw_stats[index - 3])
 
-    global fd_counts
-    fd_counts = _process_fds()
-
-
-def _process_fds():
-    counts = {(k,): 0 for k in TYPES.values()}
-    counts[("other",)] = 0
 
+def _count_fds():
     # Not every OS will have a /proc/self/fd directory
     if not HAVE_PROC_SELF_FD:
-        return counts
-
-    for fd in os.listdir("/proc/self/fd"):
-        try:
-            s = os.stat("/proc/self/fd/%s" % (fd))
-            fmt = stat.S_IFMT(s.st_mode)
-            if fmt in TYPES:
-                t = TYPES[fmt]
-            else:
-                t = "other"
+        return 0
 
-            counts[(t,)] += 1
-        except OSError:
-            # the dirh itself used by listdir() is usually missing by now
-            pass
-
-    return counts
+    return len(os.listdir("/proc/self/fd"))
 
 
 def register_process_collector(process_metrics):
-    # Legacy synapse-invented metric names
-
-    resource_metrics = process_metrics.make_subspace("resource")
-
-    resource_metrics.register_collector(update_resource_metrics)
-
-    # msecs
-    resource_metrics.register_callback("utime", lambda: rusage.ru_utime * 1000)
-    resource_metrics.register_callback("stime", lambda: rusage.ru_stime * 1000)
-
-    # kilobytes
-    resource_metrics.register_callback("maxrss", lambda: rusage.ru_maxrss * 1024)
-
-    process_metrics.register_callback("fds", _process_fds, labels=["type"])
-
-    # New prometheus-standard metric names
+    process_metrics.register_collector(update_resource_metrics)
 
     if HAVE_PROC_SELF_STAT:
         process_metrics.register_callback(
@@ -158,7 +103,7 @@ def register_process_collector(process_metrics):
     if HAVE_PROC_SELF_FD:
         process_metrics.register_callback(
             "open_fds",
-            lambda: sum(fd_counts.values())
+            lambda: _count_fds()
         )
 
     if HAVE_PROC_SELF_LIMITS:
diff --git a/synapse/rest/client/transactions.py b/synapse/rest/client/transactions.py
new file mode 100644
index 0000000000..351170edbc
--- /dev/null
+++ b/synapse/rest/client/transactions.py
@@ -0,0 +1,98 @@
+# -*- coding: utf-8 -*-
+# Copyright 2014-2016 OpenMarket Ltd
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# 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.
+
+"""This module contains logic for storing HTTP PUT transactions. This is used
+to ensure idempotency when performing PUTs using the REST API."""
+import logging
+
+from synapse.api.auth import get_access_token_from_request
+from synapse.util.async import ObservableDeferred
+
+logger = logging.getLogger(__name__)
+
+
+def get_transaction_key(request):
+    """A helper function which returns a transaction key that can be used
+    with TransactionCache for idempotent requests.
+
+    Idempotency is based on the returned key being the same for separate
+    requests to the same endpoint. The key is formed from the HTTP request
+    path and the access_token for the requesting user.
+
+    Args:
+        request (twisted.web.http.Request): The incoming request. Must
+        contain an access_token.
+    Returns:
+        str: A transaction key
+    """
+    token = get_access_token_from_request(request)
+    return request.path + "/" + token
+
+
+CLEANUP_PERIOD_MS = 1000 * 60 * 30  # 30 mins
+
+
+class HttpTransactionCache(object):
+
+    def __init__(self, clock):
+        self.clock = clock
+        self.transactions = {
+            # $txn_key: (ObservableDeferred<(res_code, res_json_body)>, timestamp)
+        }
+        # Try to clean entries every 30 mins. This means entries will exist
+        # for at *LEAST* 30 mins, and at *MOST* 60 mins.
+        self.cleaner = self.clock.looping_call(self._cleanup, CLEANUP_PERIOD_MS)
+
+    def fetch_or_execute_request(self, request, fn, *args, **kwargs):
+        """A helper function for fetch_or_execute which extracts
+        a transaction key from the given request.
+
+        See:
+            fetch_or_execute
+        """
+        return self.fetch_or_execute(
+            get_transaction_key(request), fn, *args, **kwargs
+        )
+
+    def fetch_or_execute(self, txn_key, fn, *args, **kwargs):
+        """Fetches the response for this transaction, or executes the given function
+        to produce a response for this transaction.
+
+        Args:
+            txn_key (str): A key to ensure idempotency should fetch_or_execute be
+            called again at a later point in time.
+            fn (function): A function which returns a tuple of
+            (response_code, response_dict).
+            *args: Arguments to pass to fn.
+            **kwargs: Keyword arguments to pass to fn.
+        Returns:
+            Deferred which resolves to a tuple of (response_code, response_dict).
+        """
+        try:
+            return self.transactions[txn_key][0].observe()
+        except (KeyError, IndexError):
+            pass  # execute the function instead.
+
+        deferred = fn(*args, **kwargs)
+        observable = ObservableDeferred(deferred)
+        self.transactions[txn_key] = (observable, self.clock.time_msec())
+        return observable.observe()
+
+    def _cleanup(self):
+        now = self.clock.time_msec()
+        for key in self.transactions.keys():
+            ts = self.transactions[key][1]
+            if now > (ts + CLEANUP_PERIOD_MS):  # after cleanup period
+                del self.transactions[key]
diff --git a/synapse/rest/client/v1/base.py b/synapse/rest/client/v1/base.py
index c2a8447860..c7aa0bbf59 100644
--- a/synapse/rest/client/v1/base.py
+++ b/synapse/rest/client/v1/base.py
@@ -18,7 +18,8 @@
 
 from synapse.http.servlet import RestServlet
 from synapse.api.urls import CLIENT_PREFIX
-from .transactions import HttpTransactionStore
+from synapse.rest.client.transactions import HttpTransactionCache
+
 import re
 
 import logging
@@ -59,4 +60,4 @@ class ClientV1RestServlet(RestServlet):
         self.hs = hs
         self.builder_factory = hs.get_event_builder_factory()
         self.auth = hs.get_v1auth()
-        self.txns = HttpTransactionStore()
+        self.txns = HttpTransactionCache(hs.get_clock())
diff --git a/synapse/rest/client/v1/room.py b/synapse/rest/client/v1/room.py
index 010fbc7c32..3fb1f2deb3 100644
--- a/synapse/rest/client/v1/room.py
+++ b/synapse/rest/client/v1/room.py
@@ -53,19 +53,10 @@ class RoomCreateRestServlet(ClientV1RestServlet):
                                    client_path_patterns("/createRoom(?:/.*)?$"),
                                    self.on_OPTIONS)
 
-    @defer.inlineCallbacks
     def on_PUT(self, request, txn_id):
-        try:
-            defer.returnValue(
-                self.txns.get_client_transaction(request, txn_id)
-            )
-        except KeyError:
-            pass
-
-        response = yield self.on_POST(request)
-
-        self.txns.store_client_transaction(request, txn_id, response)
-        defer.returnValue(response)
+        return self.txns.fetch_or_execute_request(
+            request, self.on_POST, request
+        )
 
     @defer.inlineCallbacks
     def on_POST(self, request):
@@ -214,19 +205,10 @@ class RoomSendEventRestServlet(ClientV1RestServlet):
     def on_GET(self, request, room_id, event_type, txn_id):
         return (200, "Not implemented")
 
-    @defer.inlineCallbacks
     def on_PUT(self, request, room_id, event_type, txn_id):
-        try:
-            defer.returnValue(
-                self.txns.get_client_transaction(request, txn_id)
-            )
-        except KeyError:
-            pass
-
-        response = yield self.on_POST(request, room_id, event_type, txn_id)
-
-        self.txns.store_client_transaction(request, txn_id, response)
-        defer.returnValue(response)
+        return self.txns.fetch_or_execute_request(
+            request, self.on_POST, request, room_id, event_type, txn_id
+        )
 
 
 # TODO: Needs unit testing for room ID + alias joins
@@ -283,19 +265,10 @@ class JoinRoomAliasServlet(ClientV1RestServlet):
 
         defer.returnValue((200, {"room_id": room_id}))
 
-    @defer.inlineCallbacks
     def on_PUT(self, request, room_identifier, txn_id):
-        try:
-            defer.returnValue(
-                self.txns.get_client_transaction(request, txn_id)
-            )
-        except KeyError:
-            pass
-
-        response = yield self.on_POST(request, room_identifier, txn_id)
-
-        self.txns.store_client_transaction(request, txn_id, response)
-        defer.returnValue(response)
+        return self.txns.fetch_or_execute_request(
+            request, self.on_POST, request, room_identifier, txn_id
+        )
 
 
 # TODO: Needs unit testing
@@ -537,22 +510,11 @@ class RoomForgetRestServlet(ClientV1RestServlet):
 
         defer.returnValue((200, {}))
 
-    @defer.inlineCallbacks
     def on_PUT(self, request, room_id, txn_id):
-        try:
-            defer.returnValue(
-                self.txns.get_client_transaction(request, txn_id)
-            )
-        except KeyError:
-            pass
-
-        response = yield self.on_POST(
-            request, room_id, txn_id
+        return self.txns.fetch_or_execute_request(
+            request, self.on_POST, request, room_id, txn_id
         )
 
-        self.txns.store_client_transaction(request, txn_id, response)
-        defer.returnValue(response)
-
 
 # TODO: Needs unit testing
 class RoomMembershipRestServlet(ClientV1RestServlet):
@@ -623,22 +585,11 @@ class RoomMembershipRestServlet(ClientV1RestServlet):
                 return False
         return True
 
-    @defer.inlineCallbacks
     def on_PUT(self, request, room_id, membership_action, txn_id):
-        try:
-            defer.returnValue(
-                self.txns.get_client_transaction(request, txn_id)
-            )
-        except KeyError:
-            pass
-
-        response = yield self.on_POST(
-            request, room_id, membership_action, txn_id
+        return self.txns.fetch_or_execute_request(
+            request, self.on_POST, request, room_id, membership_action, txn_id
         )
 
-        self.txns.store_client_transaction(request, txn_id, response)
-        defer.returnValue(response)
-
 
 class RoomRedactEventRestServlet(ClientV1RestServlet):
     def __init__(self, hs):
@@ -669,19 +620,10 @@ class RoomRedactEventRestServlet(ClientV1RestServlet):
 
         defer.returnValue((200, {"event_id": event.event_id}))
 
-    @defer.inlineCallbacks
     def on_PUT(self, request, room_id, event_id, txn_id):
-        try:
-            defer.returnValue(
-                self.txns.get_client_transaction(request, txn_id)
-            )
-        except KeyError:
-            pass
-
-        response = yield self.on_POST(request, room_id, event_id, txn_id)
-
-        self.txns.store_client_transaction(request, txn_id, response)
-        defer.returnValue(response)
+        return self.txns.fetch_or_execute_request(
+            request, self.on_POST, request, room_id, event_id, txn_id
+        )
 
 
 class RoomTypingRestServlet(ClientV1RestServlet):
diff --git a/synapse/rest/client/v1/transactions.py b/synapse/rest/client/v1/transactions.py
deleted file mode 100644
index 2f2c9d0881..0000000000
--- a/synapse/rest/client/v1/transactions.py
+++ /dev/null
@@ -1,97 +0,0 @@
-# -*- coding: utf-8 -*-
-# Copyright 2014-2016 OpenMarket Ltd
-#
-# Licensed under the Apache License, Version 2.0 (the "License");
-# you may not use this file except in compliance with the License.
-# You may obtain a copy of the License at
-#
-#     http://www.apache.org/licenses/LICENSE-2.0
-#
-# Unless required by applicable law or agreed to in writing, software
-# distributed under the License is distributed on an "AS IS" BASIS,
-# 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.
-
-"""This module contains logic for storing HTTP PUT transactions. This is used
-to ensure idempotency when performing PUTs using the REST API."""
-import logging
-
-from synapse.api.auth import get_access_token_from_request
-
-logger = logging.getLogger(__name__)
-
-
-# FIXME: elsewhere we use FooStore to indicate something in the storage layer...
-class HttpTransactionStore(object):
-
-    def __init__(self):
-        # { key : (txn_id, response) }
-        self.transactions = {}
-
-    def get_response(self, key, txn_id):
-        """Retrieve a response for this request.
-
-        Args:
-            key (str): A transaction-independent key for this request. Usually
-                this is a combination of the path (without the transaction id)
-                and the user's access token.
-            txn_id (str): The transaction ID for this request
-        Returns:
-            A tuple of (HTTP response code, response content) or None.
-        """
-        try:
-            logger.debug("get_response TxnId: %s", txn_id)
-            (last_txn_id, response) = self.transactions[key]
-            if txn_id == last_txn_id:
-                logger.info("get_response: Returning a response for %s", txn_id)
-                return response
-        except KeyError:
-            pass
-        return None
-
-    def store_response(self, key, txn_id, response):
-        """Stores an HTTP response tuple.
-
-        Args:
-            key (str): A transaction-independent key for this request. Usually
-                this is a combination of the path (without the transaction id)
-                and the user's access token.
-            txn_id (str): The transaction ID for this request.
-            response (tuple): A tuple of (HTTP response code, response content)
-        """
-        logger.debug("store_response TxnId: %s", txn_id)
-        self.transactions[key] = (txn_id, response)
-
-    def store_client_transaction(self, request, txn_id, response):
-        """Stores the request/response pair of an HTTP transaction.
-
-        Args:
-            request (twisted.web.http.Request): The twisted HTTP request. This
-            request must have the transaction ID as the last path segment.
-            response (tuple): A tuple of (response code, response dict)
-            txn_id (str): The transaction ID for this request.
-        """
-        self.store_response(self._get_key(request), txn_id, response)
-
-    def get_client_transaction(self, request, txn_id):
-        """Retrieves a stored response if there was one.
-
-        Args:
-            request (twisted.web.http.Request): The twisted HTTP request. This
-            request must have the transaction ID as the last path segment.
-            txn_id (str): The transaction ID for this request.
-        Returns:
-            The response tuple.
-        Raises:
-            KeyError if the transaction was not found.
-        """
-        response = self.get_response(self._get_key(request), txn_id)
-        if response is None:
-            raise KeyError("Transaction not found.")
-        return response
-
-    def _get_key(self, request):
-        token = get_access_token_from_request(request)
-        path_without_txn_id = request.path.rsplit("/", 1)[0]
-        return path_without_txn_id + "/" + token
diff --git a/synapse/rest/client/v2_alpha/register.py b/synapse/rest/client/v2_alpha/register.py
index 68d18a9b82..6cfb20866b 100644
--- a/synapse/rest/client/v2_alpha/register.py
+++ b/synapse/rest/client/v2_alpha/register.py
@@ -169,6 +169,17 @@ class RegisterRestServlet(RestServlet):
 
         guest_access_token = body.get("guest_access_token", None)
 
+        if (
+            'initial_device_display_name' in body and
+            'password' not in body
+        ):
+            # ignore 'initial_device_display_name' if sent without
+            # a password to work around a client bug where it sent
+            # the 'initial_device_display_name' param alone, wiping out
+            # the original registration params
+            logger.warn("Ignoring initial_device_display_name without password")
+            del body['initial_device_display_name']
+
         session_id = self.auth_handler.get_session_id(body)
         registered_user_id = None
         if session_id:
diff --git a/synapse/rest/client/v2_alpha/sendtodevice.py b/synapse/rest/client/v2_alpha/sendtodevice.py
index 5975164b37..ac660669f3 100644
--- a/synapse/rest/client/v2_alpha/sendtodevice.py
+++ b/synapse/rest/client/v2_alpha/sendtodevice.py
@@ -19,7 +19,7 @@ from twisted.internet import defer
 
 from synapse.http import servlet
 from synapse.http.servlet import parse_json_object_from_request
-from synapse.rest.client.v1.transactions import HttpTransactionStore
+from synapse.rest.client.transactions import HttpTransactionCache
 
 from ._base import client_v2_patterns
 
@@ -40,18 +40,16 @@ class SendToDeviceRestServlet(servlet.RestServlet):
         super(SendToDeviceRestServlet, self).__init__()
         self.hs = hs
         self.auth = hs.get_auth()
-        self.txns = HttpTransactionStore()
+        self.txns = HttpTransactionCache(hs.get_clock())
         self.device_message_handler = hs.get_device_message_handler()
 
-    @defer.inlineCallbacks
     def on_PUT(self, request, message_type, txn_id):
-        try:
-            defer.returnValue(
-                self.txns.get_client_transaction(request, txn_id)
-            )
-        except KeyError:
-            pass
+        return self.txns.fetch_or_execute_request(
+            request, self._put, request, message_type, txn_id
+        )
 
+    @defer.inlineCallbacks
+    def _put(self, request, message_type, txn_id):
         requester = yield self.auth.get_user_by_req(request)
 
         content = parse_json_object_from_request(request)
@@ -63,7 +61,6 @@ class SendToDeviceRestServlet(servlet.RestServlet):
         )
 
         response = (200, {})
-        self.txns.store_client_transaction(request, txn_id, response)
         defer.returnValue(response)
 
 
diff --git a/synapse/rest/media/v1/download_resource.py b/synapse/rest/media/v1/download_resource.py
index a45ee9483e..dfb87ffd15 100644
--- a/synapse/rest/media/v1/download_resource.py
+++ b/synapse/rest/media/v1/download_resource.py
@@ -15,7 +15,7 @@
 
 from ._base import parse_media_id, respond_with_file, respond_404
 from twisted.web.resource import Resource
-from synapse.http.server import request_handler
+from synapse.http.server import request_handler, set_cors_headers
 
 from twisted.web.server import NOT_DONE_YET
 from twisted.internet import defer
@@ -45,6 +45,7 @@ class DownloadResource(Resource):
     @request_handler()
     @defer.inlineCallbacks
     def _async_render_GET(self, request):
+        set_cors_headers(request)
         request.setHeader(
             "Content-Security-Policy",
             "default-src 'none';"
diff --git a/synapse/rest/media/v1/thumbnail_resource.py b/synapse/rest/media/v1/thumbnail_resource.py
index 0b9e1de1a7..d8f54adc99 100644
--- a/synapse/rest/media/v1/thumbnail_resource.py
+++ b/synapse/rest/media/v1/thumbnail_resource.py
@@ -17,7 +17,7 @@
 from ._base import parse_media_id, respond_404, respond_with_file
 from twisted.web.resource import Resource
 from synapse.http.servlet import parse_string, parse_integer
-from synapse.http.server import request_handler
+from synapse.http.server import request_handler, set_cors_headers
 
 from twisted.web.server import NOT_DONE_YET
 from twisted.internet import defer
@@ -48,6 +48,7 @@ class ThumbnailResource(Resource):
     @request_handler()
     @defer.inlineCallbacks
     def _async_render_GET(self, request):
+        set_cors_headers(request)
         server_name, media_id, _ = parse_media_id(request)
         width = parse_integer(request, "width")
         height = parse_integer(request, "height")
diff --git a/synapse/storage/prepare_database.py b/synapse/storage/prepare_database.py
index d2c0aebe48..6576a30098 100644
--- a/synapse/storage/prepare_database.py
+++ b/synapse/storage/prepare_database.py
@@ -25,7 +25,7 @@ logger = logging.getLogger(__name__)
 
 # Remember to update this number every time a change is made to database
 # schema files, so the users will be informed on server restarts.
-SCHEMA_VERSION = 37
+SCHEMA_VERSION = 38
 
 dir_path = os.path.abspath(os.path.dirname(__file__))
 
diff --git a/synapse/storage/pusher.py b/synapse/storage/pusher.py
index 8f5f8f24a9..8cc9f0353b 100644
--- a/synapse/storage/pusher.py
+++ b/synapse/storage/pusher.py
@@ -137,17 +137,8 @@ class PusherStore(SQLBaseStore):
 
     @cachedInlineCallbacks(num_args=1, max_entries=15000)
     def get_if_user_has_pusher(self, user_id):
-        result = yield self._simple_select_many_batch(
-            table='pushers',
-            keyvalues={
-                'user_name': 'user_id',
-            },
-            retcol='user_name',
-            desc='get_if_user_has_pusher',
-            allow_none=True,
-        )
-
-        defer.returnValue(bool(result))
+        # This only exists for the cachedList decorator
+        raise NotImplementedError()
 
     @cachedList(cached_method_name="get_if_user_has_pusher",
                 list_name="user_ids", num_args=1, inlineCallbacks=True)
diff --git a/synapse/storage/schema/delta/38/postgres_fts_gist.sql b/synapse/storage/schema/delta/38/postgres_fts_gist.sql
new file mode 100644
index 0000000000..f090a7b75a
--- /dev/null
+++ b/synapse/storage/schema/delta/38/postgres_fts_gist.sql
@@ -0,0 +1,17 @@
+/* Copyright 2016 OpenMarket Ltd
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *    http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * 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.
+ */
+
+ INSERT into background_updates (update_name, progress_json)
+     VALUES ('event_search_postgres_gist', '{}');
diff --git a/synapse/storage/search.py b/synapse/storage/search.py
index 12941d1775..8f2b3c4435 100644
--- a/synapse/storage/search.py
+++ b/synapse/storage/search.py
@@ -31,6 +31,7 @@ class SearchStore(BackgroundUpdateStore):
 
     EVENT_SEARCH_UPDATE_NAME = "event_search"
     EVENT_SEARCH_ORDER_UPDATE_NAME = "event_search_order"
+    EVENT_SEARCH_USE_GIST_POSTGRES_NAME = "event_search_postgres_gist"
 
     def __init__(self, hs):
         super(SearchStore, self).__init__(hs)
@@ -41,6 +42,10 @@ class SearchStore(BackgroundUpdateStore):
             self.EVENT_SEARCH_ORDER_UPDATE_NAME,
             self._background_reindex_search_order
         )
+        self.register_background_update_handler(
+            self.EVENT_SEARCH_USE_GIST_POSTGRES_NAME,
+            self._background_reindex_gist_search
+        )
 
     @defer.inlineCallbacks
     def _background_reindex_search(self, progress, batch_size):
@@ -140,6 +145,28 @@ class SearchStore(BackgroundUpdateStore):
         defer.returnValue(result)
 
     @defer.inlineCallbacks
+    def _background_reindex_gist_search(self, progress, batch_size):
+        def create_index(conn):
+            conn.rollback()
+            conn.set_session(autocommit=True)
+            c = conn.cursor()
+
+            c.execute(
+                "CREATE INDEX CONCURRENTLY event_search_fts_idx_gist"
+                " ON event_search USING GIST (vector)"
+            )
+
+            c.execute("DROP INDEX event_search_fts_idx")
+
+            conn.set_session(autocommit=False)
+
+        if isinstance(self.database_engine, PostgresEngine):
+            yield self.runWithConnection(create_index)
+
+        yield self._end_background_update(self.EVENT_SEARCH_USE_GIST_POSTGRES_NAME)
+        defer.returnValue(1)
+
+    @defer.inlineCallbacks
     def _background_reindex_search_order(self, progress, batch_size):
         target_min_stream_id = progress["target_min_stream_id_inclusive"]
         max_stream_id = progress["max_stream_id_exclusive"]
diff --git a/synapse/storage/transactions.py b/synapse/storage/transactions.py
index 5055c04b24..adab520c78 100644
--- a/synapse/storage/transactions.py
+++ b/synapse/storage/transactions.py
@@ -16,13 +16,12 @@
 from ._base import SQLBaseStore
 from synapse.util.caches.descriptors import cached
 
-from twisted.internet import defer, reactor
+from twisted.internet import defer
 
 from canonicaljson import encode_canonical_json
 
 from collections import namedtuple
 
-import itertools
 import logging
 import ujson as json
 
@@ -50,20 +49,6 @@ class TransactionStore(SQLBaseStore):
     def __init__(self, hs):
         super(TransactionStore, self).__init__(hs)
 
-        # New transactions that are currently in flights
-        self.inflight_transactions = {}
-
-        # Newly delievered transactions that *weren't* persisted while in flight
-        self.new_delivered_transactions = {}
-
-        # Newly delivered transactions that *were* persisted while in flight
-        self.update_delivered_transactions = {}
-
-        self.last_transaction = {}
-
-        reactor.addSystemEventTrigger("before", "shutdown", self._persist_in_mem_txns)
-        self._clock.looping_call(self._persist_in_mem_txns, 1000)
-
         self._clock.looping_call(self._cleanup_transactions, 30 * 60 * 1000)
 
     def get_received_txn_response(self, transaction_id, origin):
@@ -148,46 +133,7 @@ class TransactionStore(SQLBaseStore):
         Returns:
             list: A list of previous transaction ids.
         """
-
-        auto_id = self._transaction_id_gen.get_next()
-
-        txn_row = _TransactionRow(
-            id=auto_id,
-            transaction_id=transaction_id,
-            destination=destination,
-            ts=origin_server_ts,
-            response_code=0,
-            response_json=None,
-        )
-
-        self.inflight_transactions.setdefault(destination, {})[transaction_id] = txn_row
-
-        prev_txn = self.last_transaction.get(destination)
-        if prev_txn:
-            return defer.succeed(prev_txn)
-        else:
-            return self.runInteraction(
-                "_get_prevs_txn",
-                self._get_prevs_txn,
-                destination,
-            )
-
-    def _get_prevs_txn(self, txn, destination):
-        # First we find out what the prev_txns should be.
-        # Since we know that we are only sending one transaction at a time,
-        # we can simply take the last one.
-        query = (
-            "SELECT * FROM sent_transactions"
-            " WHERE destination = ?"
-            " ORDER BY id DESC LIMIT 1"
-        )
-
-        txn.execute(query, (destination,))
-        results = self.cursor_to_dict(txn)
-
-        prev_txns = [r["transaction_id"] for r in results]
-
-        return prev_txns
+        return defer.succeed([])
 
     def delivered_txn(self, transaction_id, destination, code, response_dict):
         """Persists the response for an outgoing transaction.
@@ -198,52 +144,7 @@ class TransactionStore(SQLBaseStore):
             code (int)
             response_json (str)
         """
-
-        txn_row = self.inflight_transactions.get(
-            destination, {}
-        ).pop(transaction_id, None)
-
-        self.last_transaction[destination] = transaction_id
-
-        if txn_row:
-            d = self.new_delivered_transactions.setdefault(destination, {})
-            d[transaction_id] = txn_row._replace(
-                response_code=code,
-                response_json=None,  # For now, don't persist response
-            )
-        else:
-            d = self.update_delivered_transactions.setdefault(destination, {})
-            # For now, don't persist response
-            d[transaction_id] = _UpdateTransactionRow(code, None)
-
-    def get_transactions_after(self, transaction_id, destination):
-        """Get all transactions after a given local transaction_id.
-
-        Args:
-            transaction_id (str)
-            destination (str)
-
-        Returns:
-            list: A list of dicts
-        """
-        return self.runInteraction(
-            "get_transactions_after",
-            self._get_transactions_after, transaction_id, destination
-        )
-
-    def _get_transactions_after(self, txn, transaction_id, destination):
-        query = (
-            "SELECT * FROM sent_transactions"
-            " WHERE destination = ? AND id >"
-            " ("
-            " SELECT id FROM sent_transactions"
-            " WHERE transaction_id = ? AND destination = ?"
-            " )"
-        )
-
-        txn.execute(query, (destination, transaction_id, destination))
-
-        return self.cursor_to_dict(txn)
+        pass
 
     @cached(max_entries=10000)
     def get_destination_retry_timings(self, destination):
@@ -339,58 +240,11 @@ class TransactionStore(SQLBaseStore):
         txn.execute(query, (self._clock.time_msec(),))
         return self.cursor_to_dict(txn)
 
-    @defer.inlineCallbacks
-    def _persist_in_mem_txns(self):
-        try:
-            inflight = self.inflight_transactions
-            new_delivered = self.new_delivered_transactions
-            update_delivered = self.update_delivered_transactions
-
-            self.inflight_transactions = {}
-            self.new_delivered_transactions = {}
-            self.update_delivered_transactions = {}
-
-            full_rows = [
-                row._asdict()
-                for txn_map in itertools.chain(inflight.values(), new_delivered.values())
-                for row in txn_map.values()
-            ]
-
-            def f(txn):
-                if full_rows:
-                    self._simple_insert_many_txn(
-                        txn=txn,
-                        table="sent_transactions",
-                        values=full_rows
-                    )
-
-                for dest, txn_map in update_delivered.items():
-                    for txn_id, update_row in txn_map.items():
-                        self._simple_update_one_txn(
-                            txn,
-                            table="sent_transactions",
-                            keyvalues={
-                                "transaction_id": txn_id,
-                                "destination": dest,
-                            },
-                            updatevalues={
-                                "response_code": update_row.response_code,
-                                "response_json": None,  # For now, don't persist response
-                            }
-                        )
-
-            if full_rows or update_delivered:
-                yield self.runInteraction("_persist_in_mem_txns", f)
-        except:
-            logger.exception("Failed to persist transactions!")
-
     def _cleanup_transactions(self):
         now = self._clock.time_msec()
         month_ago = now - 30 * 24 * 60 * 60 * 1000
-        six_hours_ago = now - 6 * 60 * 60 * 1000
 
         def _cleanup_transactions_txn(txn):
             txn.execute("DELETE FROM received_transactions WHERE ts < ?", (month_ago,))
-            txn.execute("DELETE FROM sent_transactions WHERE ts < ?", (six_hours_ago,))
 
-        return self.runInteraction("_persist_in_mem_txns", _cleanup_transactions_txn)
+        return self.runInteraction("_cleanup_transactions", _cleanup_transactions_txn)
diff --git a/synapse/util/__init__.py b/synapse/util/__init__.py
index 2b3f0bef3c..c05b9450be 100644
--- a/synapse/util/__init__.py
+++ b/synapse/util/__init__.py
@@ -34,7 +34,7 @@ class Clock(object):
     """A small utility that obtains current time-of-day so that time may be
     mocked during unit-tests.
 
-    TODO(paul): Also move the sleep() functionallity into it
+    TODO(paul): Also move the sleep() functionality into it
     """
 
     def time(self):
@@ -46,6 +46,14 @@ class Clock(object):
         return int(self.time() * 1000)
 
     def looping_call(self, f, msec):
+        """Call a function repeatedly.
+
+         Waits `msec` initially before calling `f` for the first time.
+
+        Args:
+            f(function): The function to call repeatedly.
+            msec(float): How long to wait between calls in milliseconds.
+        """
         l = task.LoopingCall(f)
         l.start(msec / 1000.0, now=False)
         return l
diff --git a/tests/rest/client/test_transactions.py b/tests/rest/client/test_transactions.py
new file mode 100644
index 0000000000..d7cea30260
--- /dev/null
+++ b/tests/rest/client/test_transactions.py
@@ -0,0 +1,69 @@
+from synapse.rest.client.transactions import HttpTransactionCache
+from synapse.rest.client.transactions import CLEANUP_PERIOD_MS
+from twisted.internet import defer
+from mock import Mock, call
+from tests import unittest
+from tests.utils import MockClock
+
+
+class HttpTransactionCacheTestCase(unittest.TestCase):
+
+    def setUp(self):
+        self.clock = MockClock()
+        self.cache = HttpTransactionCache(self.clock)
+
+        self.mock_http_response = (200, "GOOD JOB!")
+        self.mock_key = "foo"
+
+    @defer.inlineCallbacks
+    def test_executes_given_function(self):
+        cb = Mock(
+            return_value=defer.succeed(self.mock_http_response)
+        )
+        res = yield self.cache.fetch_or_execute(
+            self.mock_key, cb, "some_arg", keyword="arg"
+        )
+        cb.assert_called_once_with("some_arg", keyword="arg")
+        self.assertEqual(res, self.mock_http_response)
+
+    @defer.inlineCallbacks
+    def test_deduplicates_based_on_key(self):
+        cb = Mock(
+            return_value=defer.succeed(self.mock_http_response)
+        )
+        for i in range(3):  # invoke multiple times
+            res = yield self.cache.fetch_or_execute(
+                self.mock_key, cb, "some_arg", keyword="arg", changing_args=i
+            )
+            self.assertEqual(res, self.mock_http_response)
+        # expect only a single call to do the work
+        cb.assert_called_once_with("some_arg", keyword="arg", changing_args=0)
+
+    @defer.inlineCallbacks
+    def test_cleans_up(self):
+        cb = Mock(
+            return_value=defer.succeed(self.mock_http_response)
+        )
+        yield self.cache.fetch_or_execute(
+            self.mock_key, cb, "an arg"
+        )
+        # should NOT have cleaned up yet
+        self.clock.advance_time_msec(CLEANUP_PERIOD_MS / 2)
+
+        yield self.cache.fetch_or_execute(
+            self.mock_key, cb, "an arg"
+        )
+        # still using cache
+        cb.assert_called_once_with("an arg")
+
+        self.clock.advance_time_msec(CLEANUP_PERIOD_MS)
+
+        yield self.cache.fetch_or_execute(
+            self.mock_key, cb, "an arg"
+        )
+        # no longer using cache
+        self.assertEqual(cb.call_count, 2)
+        self.assertEqual(
+            cb.call_args_list,
+            [call("an arg",), call("an arg",)]
+        )