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-rw-r--r--synapse/events/snapshot.py4
-rw-r--r--synapse/handlers/directory.py7
-rw-r--r--synapse/handlers/federation.py43
-rw-r--r--synapse/handlers/message.py321
-rw-r--r--synapse/handlers/room.py11
-rw-r--r--synapse/handlers/room_member.py21
-rw-r--r--synapse/http/servlet.py18
-rw-r--r--synapse/python_dependencies.py2
-rw-r--r--synapse/replication/slave/storage/events.py4
-rw-r--r--synapse/rest/client/v1/admin.py14
-rw-r--r--synapse/rest/client/v1/room.py17
-rw-r--r--synapse/rest/media/v1/media_storage.py6
-rw-r--r--synapse/server.py5
-rw-r--r--synapse/state.py56
-rw-r--r--synapse/storage/__init__.py1
-rw-r--r--synapse/storage/engines/postgres.py6
-rw-r--r--synapse/storage/engines/sqlite3.py19
-rw-r--r--synapse/storage/events.py104
-rw-r--r--synapse/storage/room.py43
-rw-r--r--synapse/storage/schema/delta/47/state_group_seq.py37
-rw-r--r--synapse/storage/search.py110
-rw-r--r--synapse/storage/state.py196
22 files changed, 634 insertions, 411 deletions
diff --git a/synapse/events/snapshot.py b/synapse/events/snapshot.py
index e9a732ff03..87e3fe7b97 100644
--- a/synapse/events/snapshot.py
+++ b/synapse/events/snapshot.py
@@ -25,7 +25,9 @@ class EventContext(object):
             The current state map excluding the current event.
             (type, state_key) -> event_id
 
-        state_group (int): state group id
+        state_group (int|None): state group id, if the state has been stored
+            as a state group. This is usually only None if e.g. the event is
+            an outlier.
         rejected (bool|str): A rejection reason if the event was rejected, else
             False
 
diff --git a/synapse/handlers/directory.py b/synapse/handlers/directory.py
index a0464ae5c0..8580ada60a 100644
--- a/synapse/handlers/directory.py
+++ b/synapse/handlers/directory.py
@@ -34,6 +34,7 @@ class DirectoryHandler(BaseHandler):
 
         self.state = hs.get_state_handler()
         self.appservice_handler = hs.get_application_service_handler()
+        self.event_creation_handler = hs.get_event_creation_handler()
 
         self.federation = hs.get_replication_layer()
         self.federation.register_query_handler(
@@ -249,8 +250,7 @@ class DirectoryHandler(BaseHandler):
     def send_room_alias_update_event(self, requester, user_id, room_id):
         aliases = yield self.store.get_aliases_for_room(room_id)
 
-        msg_handler = self.hs.get_handlers().message_handler
-        yield msg_handler.create_and_send_nonmember_event(
+        yield self.event_creation_handler.create_and_send_nonmember_event(
             requester,
             {
                 "type": EventTypes.Aliases,
@@ -272,8 +272,7 @@ class DirectoryHandler(BaseHandler):
         if not alias_event or alias_event.content.get("alias", "") != alias_str:
             return
 
-        msg_handler = self.hs.get_handlers().message_handler
-        yield msg_handler.create_and_send_nonmember_event(
+        yield self.event_creation_handler.create_and_send_nonmember_event(
             requester,
             {
                 "type": EventTypes.CanonicalAlias,
diff --git a/synapse/handlers/federation.py b/synapse/handlers/federation.py
index 8ee9434c9b..46bcf8b081 100644
--- a/synapse/handlers/federation.py
+++ b/synapse/handlers/federation.py
@@ -1,5 +1,6 @@
 # -*- coding: utf-8 -*-
 # Copyright 2014-2016 OpenMarket Ltd
+# Copyright 2018 New Vector Ltd
 #
 # Licensed under the Apache License, Version 2.0 (the "License");
 # you may not use this file except in compliance with the License.
@@ -75,6 +76,7 @@ class FederationHandler(BaseHandler):
         self.is_mine_id = hs.is_mine_id
         self.pusher_pool = hs.get_pusherpool()
         self.spam_checker = hs.get_spam_checker()
+        self.event_creation_handler = hs.get_event_creation_handler()
 
         self.replication_layer.set_handler(self)
 
@@ -1007,8 +1009,7 @@ class FederationHandler(BaseHandler):
         })
 
         try:
-            message_handler = self.hs.get_handlers().message_handler
-            event, context = yield message_handler._create_new_client_event(
+            event, context = yield self.event_creation_handler.create_new_client_event(
                 builder=builder,
             )
         except AuthError as e:
@@ -1248,8 +1249,7 @@ class FederationHandler(BaseHandler):
             "state_key": user_id,
         })
 
-        message_handler = self.hs.get_handlers().message_handler
-        event, context = yield message_handler._create_new_client_event(
+        event, context = yield self.event_creation_handler.create_new_client_event(
             builder=builder,
         )
 
@@ -1831,8 +1831,8 @@ class FederationHandler(BaseHandler):
                 current_state = set(e.event_id for e in auth_events.values())
                 different_auth = event_auth_events - current_state
 
-                self._update_context_for_auth_events(
-                    context, auth_events, event_key,
+                yield self._update_context_for_auth_events(
+                    event, context, auth_events, event_key,
                 )
 
         if different_auth and not event.internal_metadata.is_outlier():
@@ -1913,8 +1913,8 @@ class FederationHandler(BaseHandler):
                 # 4. Look at rejects and their proofs.
                 # TODO.
 
-                self._update_context_for_auth_events(
-                    context, auth_events, event_key,
+                yield self._update_context_for_auth_events(
+                    event, context, auth_events, event_key,
                 )
 
         try:
@@ -1923,11 +1923,15 @@ class FederationHandler(BaseHandler):
             logger.warn("Failed auth resolution for %r because %s", event, e)
             raise e
 
-    def _update_context_for_auth_events(self, context, auth_events,
+    @defer.inlineCallbacks
+    def _update_context_for_auth_events(self, event, context, auth_events,
                                         event_key):
-        """Update the state_ids in an event context after auth event resolution
+        """Update the state_ids in an event context after auth event resolution,
+        storing the changes as a new state group.
 
         Args:
+            event (Event): The event we're handling the context for
+
             context (synapse.events.snapshot.EventContext): event context
                 to be updated
 
@@ -1950,7 +1954,13 @@ class FederationHandler(BaseHandler):
         context.prev_state_ids.update({
             k: a.event_id for k, a in auth_events.iteritems()
         })
-        context.state_group = self.store.get_next_state_group()
+        context.state_group = yield self.store.store_state_group(
+            event.event_id,
+            event.room_id,
+            prev_group=context.prev_group,
+            delta_ids=context.delta_ids,
+            current_state_ids=context.current_state_ids,
+        )
 
     @defer.inlineCallbacks
     def construct_auth_difference(self, local_auth, remote_auth):
@@ -2120,8 +2130,7 @@ class FederationHandler(BaseHandler):
         if (yield self.auth.check_host_in_room(room_id, self.hs.hostname)):
             builder = self.event_builder_factory.new(event_dict)
             EventValidator().validate_new(builder)
-            message_handler = self.hs.get_handlers().message_handler
-            event, context = yield message_handler._create_new_client_event(
+            event, context = yield self.event_creation_handler.create_new_client_event(
                 builder=builder
             )
 
@@ -2159,8 +2168,7 @@ class FederationHandler(BaseHandler):
         """
         builder = self.event_builder_factory.new(event_dict)
 
-        message_handler = self.hs.get_handlers().message_handler
-        event, context = yield message_handler._create_new_client_event(
+        event, context = yield self.event_creation_handler.create_new_client_event(
             builder=builder,
         )
 
@@ -2210,8 +2218,9 @@ class FederationHandler(BaseHandler):
 
         builder = self.event_builder_factory.new(event_dict)
         EventValidator().validate_new(builder)
-        message_handler = self.hs.get_handlers().message_handler
-        event, context = yield message_handler._create_new_client_event(builder=builder)
+        event, context = yield self.event_creation_handler.create_new_client_event(
+            builder=builder,
+        )
         defer.returnValue((event, context))
 
     @defer.inlineCallbacks
diff --git a/synapse/handlers/message.py b/synapse/handlers/message.py
index 21f1717dd2..4e9752ccbd 100644
--- a/synapse/handlers/message.py
+++ b/synapse/handlers/message.py
@@ -1,6 +1,6 @@
 # -*- coding: utf-8 -*-
 # Copyright 2014 - 2016 OpenMarket Ltd
-# Copyright 2017 New Vector Ltd
+# Copyright 2017 - 2018 New Vector Ltd
 #
 # Licensed under the Apache License, Version 2.0 (the "License");
 # you may not use this file except in compliance with the License.
@@ -47,23 +47,11 @@ class MessageHandler(BaseHandler):
         self.hs = hs
         self.state = hs.get_state_handler()
         self.clock = hs.get_clock()
-        self.validator = EventValidator()
-        self.profile_handler = hs.get_profile_handler()
 
         self.pagination_lock = ReadWriteLock()
 
-        self.pusher_pool = hs.get_pusherpool()
-
-        # We arbitrarily limit concurrent event creation for a room to 5.
-        # This is to stop us from diverging history *too* much.
-        self.limiter = Limiter(max_count=5)
-
-        self.action_generator = hs.get_action_generator()
-
-        self.spam_checker = hs.get_spam_checker()
-
     @defer.inlineCallbacks
-    def purge_history(self, room_id, event_id):
+    def purge_history(self, room_id, event_id, delete_local_events=False):
         event = yield self.store.get_event(event_id)
 
         if event.room_id != room_id:
@@ -72,7 +60,7 @@ class MessageHandler(BaseHandler):
         depth = event.depth
 
         with (yield self.pagination_lock.write(room_id)):
-            yield self.store.delete_old_state(room_id, depth)
+            yield self.store.purge_history(room_id, depth, delete_local_events)
 
     @defer.inlineCallbacks
     def get_messages(self, requester, room_id=None, pagin_config=None,
@@ -183,6 +171,162 @@ class MessageHandler(BaseHandler):
         defer.returnValue(chunk)
 
     @defer.inlineCallbacks
+    def get_room_data(self, user_id=None, room_id=None,
+                      event_type=None, state_key="", is_guest=False):
+        """ Get data from a room.
+
+        Args:
+            event : The room path event
+        Returns:
+            The path data content.
+        Raises:
+            SynapseError if something went wrong.
+        """
+        membership, membership_event_id = yield self._check_in_room_or_world_readable(
+            room_id, user_id
+        )
+
+        if membership == Membership.JOIN:
+            data = yield self.state_handler.get_current_state(
+                room_id, event_type, state_key
+            )
+        elif membership == Membership.LEAVE:
+            key = (event_type, state_key)
+            room_state = yield self.store.get_state_for_events(
+                [membership_event_id], [key]
+            )
+            data = room_state[membership_event_id].get(key)
+
+        defer.returnValue(data)
+
+    @defer.inlineCallbacks
+    def _check_in_room_or_world_readable(self, room_id, user_id):
+        try:
+            # check_user_was_in_room will return the most recent membership
+            # event for the user if:
+            #  * The user is a non-guest user, and was ever in the room
+            #  * The user is a guest user, and has joined the room
+            # else it will throw.
+            member_event = yield self.auth.check_user_was_in_room(room_id, user_id)
+            defer.returnValue((member_event.membership, member_event.event_id))
+            return
+        except AuthError:
+            visibility = yield self.state_handler.get_current_state(
+                room_id, EventTypes.RoomHistoryVisibility, ""
+            )
+            if (
+                visibility and
+                visibility.content["history_visibility"] == "world_readable"
+            ):
+                defer.returnValue((Membership.JOIN, None))
+                return
+            raise AuthError(
+                403, "Guest access not allowed", errcode=Codes.GUEST_ACCESS_FORBIDDEN
+            )
+
+    @defer.inlineCallbacks
+    def get_state_events(self, user_id, room_id, is_guest=False):
+        """Retrieve all state events for a given room. If the user is
+        joined to the room then return the current state. If the user has
+        left the room return the state events from when they left.
+
+        Args:
+            user_id(str): The user requesting state events.
+            room_id(str): The room ID to get all state events from.
+        Returns:
+            A list of dicts representing state events. [{}, {}, {}]
+        """
+        membership, membership_event_id = yield self._check_in_room_or_world_readable(
+            room_id, user_id
+        )
+
+        if membership == Membership.JOIN:
+            room_state = yield self.state_handler.get_current_state(room_id)
+        elif membership == Membership.LEAVE:
+            room_state = yield self.store.get_state_for_events(
+                [membership_event_id], None
+            )
+            room_state = room_state[membership_event_id]
+
+        now = self.clock.time_msec()
+        defer.returnValue(
+            [serialize_event(c, now) for c in room_state.values()]
+        )
+
+    @defer.inlineCallbacks
+    def get_joined_members(self, requester, room_id):
+        """Get all the joined members in the room and their profile information.
+
+        If the user has left the room return the state events from when they left.
+
+        Args:
+            requester(Requester): The user requesting state events.
+            room_id(str): The room ID to get all state events from.
+        Returns:
+            A dict of user_id to profile info
+        """
+        user_id = requester.user.to_string()
+        if not requester.app_service:
+            # We check AS auth after fetching the room membership, as it
+            # requires us to pull out all joined members anyway.
+            membership, _ = yield self._check_in_room_or_world_readable(
+                room_id, user_id
+            )
+            if membership != Membership.JOIN:
+                raise NotImplementedError(
+                    "Getting joined members after leaving is not implemented"
+                )
+
+        users_with_profile = yield self.state.get_current_user_in_room(room_id)
+
+        # If this is an AS, double check that they are allowed to see the members.
+        # This can either be because the AS user is in the room or becuase there
+        # is a user in the room that the AS is "interested in"
+        if requester.app_service and user_id not in users_with_profile:
+            for uid in users_with_profile:
+                if requester.app_service.is_interested_in_user(uid):
+                    break
+            else:
+                # Loop fell through, AS has no interested users in room
+                raise AuthError(403, "Appservice not in room")
+
+        defer.returnValue({
+            user_id: {
+                "avatar_url": profile.avatar_url,
+                "display_name": profile.display_name,
+            }
+            for user_id, profile in users_with_profile.iteritems()
+        })
+
+
+class EventCreationHandler(object):
+    def __init__(self, hs):
+        self.hs = hs
+        self.auth = hs.get_auth()
+        self.store = hs.get_datastore()
+        self.state = hs.get_state_handler()
+        self.clock = hs.get_clock()
+        self.validator = EventValidator()
+        self.profile_handler = hs.get_profile_handler()
+        self.event_builder_factory = hs.get_event_builder_factory()
+        self.server_name = hs.hostname
+        self.ratelimiter = hs.get_ratelimiter()
+        self.notifier = hs.get_notifier()
+
+        # This is only used to get at ratelimit function, and maybe_kick_guest_users
+        self.base_handler = BaseHandler(hs)
+
+        self.pusher_pool = hs.get_pusherpool()
+
+        # We arbitrarily limit concurrent event creation for a room to 5.
+        # This is to stop us from diverging history *too* much.
+        self.limiter = Limiter(max_count=5)
+
+        self.action_generator = hs.get_action_generator()
+
+        self.spam_checker = hs.get_spam_checker()
+
+    @defer.inlineCallbacks
     def create_event(self, requester, event_dict, token_id=None, txn_id=None,
                      prev_event_ids=None):
         """
@@ -234,7 +378,7 @@ class MessageHandler(BaseHandler):
             if txn_id is not None:
                 builder.internal_metadata.txn_id = txn_id
 
-            event, context = yield self._create_new_client_event(
+            event, context = yield self.create_new_client_event(
                 builder=builder,
                 requester=requester,
                 prev_event_ids=prev_event_ids,
@@ -259,11 +403,6 @@ class MessageHandler(BaseHandler):
                 "Tried to send member event through non-member codepath"
             )
 
-        # We check here if we are currently being rate limited, so that we
-        # don't do unnecessary work. We check again just before we actually
-        # send the event.
-        yield self.ratelimit(requester, update=False)
-
         user = UserID.from_string(event.sender)
 
         assert self.hs.is_mine(user), "User must be our own: %s" % (user,)
@@ -342,137 +481,9 @@ class MessageHandler(BaseHandler):
         )
         defer.returnValue(event)
 
+    @measure_func("create_new_client_event")
     @defer.inlineCallbacks
-    def get_room_data(self, user_id=None, room_id=None,
-                      event_type=None, state_key="", is_guest=False):
-        """ Get data from a room.
-
-        Args:
-            event : The room path event
-        Returns:
-            The path data content.
-        Raises:
-            SynapseError if something went wrong.
-        """
-        membership, membership_event_id = yield self._check_in_room_or_world_readable(
-            room_id, user_id
-        )
-
-        if membership == Membership.JOIN:
-            data = yield self.state_handler.get_current_state(
-                room_id, event_type, state_key
-            )
-        elif membership == Membership.LEAVE:
-            key = (event_type, state_key)
-            room_state = yield self.store.get_state_for_events(
-                [membership_event_id], [key]
-            )
-            data = room_state[membership_event_id].get(key)
-
-        defer.returnValue(data)
-
-    @defer.inlineCallbacks
-    def _check_in_room_or_world_readable(self, room_id, user_id):
-        try:
-            # check_user_was_in_room will return the most recent membership
-            # event for the user if:
-            #  * The user is a non-guest user, and was ever in the room
-            #  * The user is a guest user, and has joined the room
-            # else it will throw.
-            member_event = yield self.auth.check_user_was_in_room(room_id, user_id)
-            defer.returnValue((member_event.membership, member_event.event_id))
-            return
-        except AuthError:
-            visibility = yield self.state_handler.get_current_state(
-                room_id, EventTypes.RoomHistoryVisibility, ""
-            )
-            if (
-                visibility and
-                visibility.content["history_visibility"] == "world_readable"
-            ):
-                defer.returnValue((Membership.JOIN, None))
-                return
-            raise AuthError(
-                403, "Guest access not allowed", errcode=Codes.GUEST_ACCESS_FORBIDDEN
-            )
-
-    @defer.inlineCallbacks
-    def get_state_events(self, user_id, room_id, is_guest=False):
-        """Retrieve all state events for a given room. If the user is
-        joined to the room then return the current state. If the user has
-        left the room return the state events from when they left.
-
-        Args:
-            user_id(str): The user requesting state events.
-            room_id(str): The room ID to get all state events from.
-        Returns:
-            A list of dicts representing state events. [{}, {}, {}]
-        """
-        membership, membership_event_id = yield self._check_in_room_or_world_readable(
-            room_id, user_id
-        )
-
-        if membership == Membership.JOIN:
-            room_state = yield self.state_handler.get_current_state(room_id)
-        elif membership == Membership.LEAVE:
-            room_state = yield self.store.get_state_for_events(
-                [membership_event_id], None
-            )
-            room_state = room_state[membership_event_id]
-
-        now = self.clock.time_msec()
-        defer.returnValue(
-            [serialize_event(c, now) for c in room_state.values()]
-        )
-
-    @defer.inlineCallbacks
-    def get_joined_members(self, requester, room_id):
-        """Get all the joined members in the room and their profile information.
-
-        If the user has left the room return the state events from when they left.
-
-        Args:
-            requester(Requester): The user requesting state events.
-            room_id(str): The room ID to get all state events from.
-        Returns:
-            A dict of user_id to profile info
-        """
-        user_id = requester.user.to_string()
-        if not requester.app_service:
-            # We check AS auth after fetching the room membership, as it
-            # requires us to pull out all joined members anyway.
-            membership, _ = yield self._check_in_room_or_world_readable(
-                room_id, user_id
-            )
-            if membership != Membership.JOIN:
-                raise NotImplementedError(
-                    "Getting joined members after leaving is not implemented"
-                )
-
-        users_with_profile = yield self.state.get_current_user_in_room(room_id)
-
-        # If this is an AS, double check that they are allowed to see the members.
-        # This can either be because the AS user is in the room or becuase there
-        # is a user in the room that the AS is "interested in"
-        if requester.app_service and user_id not in users_with_profile:
-            for uid in users_with_profile:
-                if requester.app_service.is_interested_in_user(uid):
-                    break
-            else:
-                # Loop fell through, AS has no interested users in room
-                raise AuthError(403, "Appservice not in room")
-
-        defer.returnValue({
-            user_id: {
-                "avatar_url": profile.avatar_url,
-                "display_name": profile.display_name,
-            }
-            for user_id, profile in users_with_profile.iteritems()
-        })
-
-    @measure_func("_create_new_client_event")
-    @defer.inlineCallbacks
-    def _create_new_client_event(self, builder, requester=None, prev_event_ids=None):
+    def create_new_client_event(self, builder, requester=None, prev_event_ids=None):
         if prev_event_ids:
             prev_events = yield self.store.add_event_hashes(prev_event_ids)
             prev_max_depth = yield self.store.get_max_depth_of_events(prev_event_ids)
@@ -509,9 +520,7 @@ class MessageHandler(BaseHandler):
         builder.prev_events = prev_events
         builder.depth = depth
 
-        state_handler = self.state_handler
-
-        context = yield state_handler.compute_event_context(builder)
+        context = yield self.state.compute_event_context(builder)
         if requester:
             context.app_service = requester.app_service
 
@@ -551,7 +560,7 @@ class MessageHandler(BaseHandler):
         # We now need to go and hit out to wherever we need to hit out to.
 
         if ratelimit:
-            yield self.ratelimit(requester)
+            yield self.base_handler.ratelimit(requester)
 
         try:
             yield self.auth.check_from_context(event, context)
@@ -567,7 +576,7 @@ class MessageHandler(BaseHandler):
             logger.exception("Failed to encode content: %r", event.content)
             raise
 
-        yield self.maybe_kick_guest_users(event, context)
+        yield self.base_handler.maybe_kick_guest_users(event, context)
 
         if event.type == EventTypes.CanonicalAlias:
             # Check the alias is acually valid (at this time at least)
diff --git a/synapse/handlers/room.py b/synapse/handlers/room.py
index d1cc87a016..6ab020bf41 100644
--- a/synapse/handlers/room.py
+++ b/synapse/handlers/room.py
@@ -1,5 +1,6 @@
 # -*- coding: utf-8 -*-
 # Copyright 2014 - 2016 OpenMarket Ltd
+# Copyright 2018 New Vector Ltd
 #
 # Licensed under the Apache License, Version 2.0 (the "License");
 # you may not use this file except in compliance with the License.
@@ -64,6 +65,7 @@ class RoomCreationHandler(BaseHandler):
         super(RoomCreationHandler, self).__init__(hs)
 
         self.spam_checker = hs.get_spam_checker()
+        self.event_creation_handler = hs.get_event_creation_handler()
 
     @defer.inlineCallbacks
     def create_room(self, requester, config, ratelimit=True):
@@ -163,13 +165,11 @@ class RoomCreationHandler(BaseHandler):
 
         creation_content = config.get("creation_content", {})
 
-        msg_handler = self.hs.get_handlers().message_handler
         room_member_handler = self.hs.get_handlers().room_member_handler
 
         yield self._send_events_for_new_room(
             requester,
             room_id,
-            msg_handler,
             room_member_handler,
             preset_config=preset_config,
             invite_list=invite_list,
@@ -181,7 +181,7 @@ class RoomCreationHandler(BaseHandler):
 
         if "name" in config:
             name = config["name"]
-            yield msg_handler.create_and_send_nonmember_event(
+            yield self.event_creation_handler.create_and_send_nonmember_event(
                 requester,
                 {
                     "type": EventTypes.Name,
@@ -194,7 +194,7 @@ class RoomCreationHandler(BaseHandler):
 
         if "topic" in config:
             topic = config["topic"]
-            yield msg_handler.create_and_send_nonmember_event(
+            yield self.event_creation_handler.create_and_send_nonmember_event(
                 requester,
                 {
                     "type": EventTypes.Topic,
@@ -249,7 +249,6 @@ class RoomCreationHandler(BaseHandler):
             self,
             creator,  # A Requester object.
             room_id,
-            msg_handler,
             room_member_handler,
             preset_config,
             invite_list,
@@ -272,7 +271,7 @@ class RoomCreationHandler(BaseHandler):
         @defer.inlineCallbacks
         def send(etype, content, **kwargs):
             event = create(etype, content, **kwargs)
-            yield msg_handler.create_and_send_nonmember_event(
+            yield self.event_creation_handler.create_and_send_nonmember_event(
                 creator,
                 event,
                 ratelimit=False
diff --git a/synapse/handlers/room_member.py b/synapse/handlers/room_member.py
index 7e6467cd1d..37dc5e99ab 100644
--- a/synapse/handlers/room_member.py
+++ b/synapse/handlers/room_member.py
@@ -1,5 +1,6 @@
 # -*- coding: utf-8 -*-
 # Copyright 2016 OpenMarket Ltd
+# Copyright 2018 New Vector Ltd
 #
 # Licensed under the Apache License, Version 2.0 (the "License");
 # you may not use this file except in compliance with the License.
@@ -46,6 +47,7 @@ class RoomMemberHandler(BaseHandler):
         super(RoomMemberHandler, self).__init__(hs)
 
         self.profile_handler = hs.get_profile_handler()
+        self.event_creation_hander = hs.get_event_creation_handler()
 
         self.member_linearizer = Linearizer(name="member")
 
@@ -66,13 +68,12 @@ class RoomMemberHandler(BaseHandler):
     ):
         if content is None:
             content = {}
-        msg_handler = self.hs.get_handlers().message_handler
 
         content["membership"] = membership
         if requester.is_guest:
             content["kind"] = "guest"
 
-        event, context = yield msg_handler.create_event(
+        event, context = yield self.event_creation_hander.create_event(
             requester,
             {
                 "type": EventTypes.Member,
@@ -90,12 +91,14 @@ class RoomMemberHandler(BaseHandler):
         )
 
         # Check if this event matches the previous membership event for the user.
-        duplicate = yield msg_handler.deduplicate_state_event(event, context)
+        duplicate = yield self.event_creation_hander.deduplicate_state_event(
+            event, context,
+        )
         if duplicate is not None:
             # Discard the new event since this membership change is a no-op.
             defer.returnValue(duplicate)
 
-        yield msg_handler.handle_new_client_event(
+        yield self.event_creation_hander.handle_new_client_event(
             requester,
             event,
             context,
@@ -394,8 +397,9 @@ class RoomMemberHandler(BaseHandler):
         else:
             requester = synapse.types.create_requester(target_user)
 
-        message_handler = self.hs.get_handlers().message_handler
-        prev_event = yield message_handler.deduplicate_state_event(event, context)
+        prev_event = yield self.event_creation_hander.deduplicate_state_event(
+            event, context,
+        )
         if prev_event is not None:
             return
 
@@ -412,7 +416,7 @@ class RoomMemberHandler(BaseHandler):
             if is_blocked:
                 raise SynapseError(403, "This room has been blocked on this server")
 
-        yield message_handler.handle_new_client_event(
+        yield self.event_creation_hander.handle_new_client_event(
             requester,
             event,
             context,
@@ -644,8 +648,7 @@ class RoomMemberHandler(BaseHandler):
             )
         )
 
-        msg_handler = self.hs.get_handlers().message_handler
-        yield msg_handler.create_and_send_nonmember_event(
+        yield self.event_creation_hander.create_and_send_nonmember_event(
             requester,
             {
                 "type": EventTypes.ThirdPartyInvite,
diff --git a/synapse/http/servlet.py b/synapse/http/servlet.py
index 71420e54db..ef8e62901b 100644
--- a/synapse/http/servlet.py
+++ b/synapse/http/servlet.py
@@ -148,11 +148,13 @@ def parse_string_from_args(args, name, default=None, required=False,
             return default
 
 
-def parse_json_value_from_request(request):
+def parse_json_value_from_request(request, allow_empty_body=False):
     """Parse a JSON value from the body of a twisted HTTP request.
 
     Args:
         request: the twisted HTTP request.
+        allow_empty_body (bool): if True, an empty body will be accepted and
+            turned into None
 
     Returns:
         The JSON value.
@@ -165,6 +167,9 @@ def parse_json_value_from_request(request):
     except Exception:
         raise SynapseError(400, "Error reading JSON content.")
 
+    if not content_bytes and allow_empty_body:
+        return None
+
     try:
         content = simplejson.loads(content_bytes)
     except Exception as e:
@@ -174,17 +179,24 @@ def parse_json_value_from_request(request):
     return content
 
 
-def parse_json_object_from_request(request):
+def parse_json_object_from_request(request, allow_empty_body=False):
     """Parse a JSON object from the body of a twisted HTTP request.
 
     Args:
         request: the twisted HTTP request.
+        allow_empty_body (bool): if True, an empty body will be accepted and
+            turned into an empty dict.
 
     Raises:
         SynapseError if the request body couldn't be decoded as JSON or
             if it wasn't a JSON object.
     """
-    content = parse_json_value_from_request(request)
+    content = parse_json_value_from_request(
+        request, allow_empty_body=allow_empty_body,
+    )
+
+    if allow_empty_body and content is None:
+        return {}
 
     if type(content) != dict:
         message = "Content must be a JSON object."
diff --git a/synapse/python_dependencies.py b/synapse/python_dependencies.py
index 7052333c19..97b631e60d 100644
--- a/synapse/python_dependencies.py
+++ b/synapse/python_dependencies.py
@@ -36,7 +36,7 @@ REQUIREMENTS = {
     "pydenticon": ["pydenticon"],
     "ujson": ["ujson"],
     "blist": ["blist"],
-    "pysaml2>=3.0.0,<4.0.0": ["saml2>=3.0.0,<4.0.0"],
+    "pysaml2>=3.0.0": ["saml2>=3.0.0"],
     "pymacaroons-pynacl": ["pymacaroons"],
     "msgpack-python>=0.3.0": ["msgpack"],
     "phonenumbers>=8.2.0": ["phonenumbers"],
diff --git a/synapse/replication/slave/storage/events.py b/synapse/replication/slave/storage/events.py
index 29d7296b43..8acb5df0f3 100644
--- a/synapse/replication/slave/storage/events.py
+++ b/synapse/replication/slave/storage/events.py
@@ -19,7 +19,7 @@ from synapse.storage import DataStore
 from synapse.storage.event_federation import EventFederationStore
 from synapse.storage.event_push_actions import EventPushActionsStore
 from synapse.storage.roommember import RoomMemberStore
-from synapse.storage.state import StateGroupReadStore
+from synapse.storage.state import StateGroupWorkerStore
 from synapse.storage.stream import StreamStore
 from synapse.util.caches.stream_change_cache import StreamChangeCache
 from ._base import BaseSlavedStore
@@ -37,7 +37,7 @@ logger = logging.getLogger(__name__)
 # the method descriptor on the DataStore and chuck them into our class.
 
 
-class SlavedEventStore(StateGroupReadStore, BaseSlavedStore):
+class SlavedEventStore(StateGroupWorkerStore, BaseSlavedStore):
 
     def __init__(self, db_conn, hs):
         super(SlavedEventStore, self).__init__(db_conn, hs)
diff --git a/synapse/rest/client/v1/admin.py b/synapse/rest/client/v1/admin.py
index 0615e5d807..6073cc6fa2 100644
--- a/synapse/rest/client/v1/admin.py
+++ b/synapse/rest/client/v1/admin.py
@@ -1,5 +1,6 @@
 # -*- coding: utf-8 -*-
 # Copyright 2014-2016 OpenMarket Ltd
+# Copyright 2018 New Vector Ltd
 #
 # Licensed under the Apache License, Version 2.0 (the "License");
 # you may not use this file except in compliance with the License.
@@ -128,7 +129,14 @@ class PurgeHistoryRestServlet(ClientV1RestServlet):
         if not is_admin:
             raise AuthError(403, "You are not a server admin")
 
-        yield self.handlers.message_handler.purge_history(room_id, event_id)
+        body = parse_json_object_from_request(request, allow_empty_body=True)
+
+        delete_local_events = bool(body.get("delete_local_events", False))
+
+        yield self.handlers.message_handler.purge_history(
+            room_id, event_id,
+            delete_local_events=delete_local_events,
+        )
 
         defer.returnValue((200, {}))
 
@@ -171,6 +179,7 @@ class ShutdownRoomRestServlet(ClientV1RestServlet):
         self.store = hs.get_datastore()
         self.handlers = hs.get_handlers()
         self.state = hs.get_state_handler()
+        self.event_creation_handler = hs.get_event_creation_handler()
 
     @defer.inlineCallbacks
     def on_POST(self, request, room_id):
@@ -203,8 +212,7 @@ class ShutdownRoomRestServlet(ClientV1RestServlet):
         )
         new_room_id = info["room_id"]
 
-        msg_handler = self.handlers.message_handler
-        yield msg_handler.create_and_send_nonmember_event(
+        yield self.event_creation_handler.create_and_send_nonmember_event(
             room_creator_requester,
             {
                 "type": "m.room.message",
diff --git a/synapse/rest/client/v1/room.py b/synapse/rest/client/v1/room.py
index 867ec8602c..fbb2fc36e4 100644
--- a/synapse/rest/client/v1/room.py
+++ b/synapse/rest/client/v1/room.py
@@ -1,5 +1,6 @@
 # -*- coding: utf-8 -*-
 # Copyright 2014-2016 OpenMarket Ltd
+# Copyright 2018 New Vector Ltd
 #
 # Licensed under the Apache License, Version 2.0 (the "License");
 # you may not use this file except in compliance with the License.
@@ -82,6 +83,7 @@ class RoomStateEventRestServlet(ClientV1RestServlet):
     def __init__(self, hs):
         super(RoomStateEventRestServlet, self).__init__(hs)
         self.handlers = hs.get_handlers()
+        self.event_creation_hander = hs.get_event_creation_handler()
 
     def register(self, http_server):
         # /room/$roomid/state/$eventtype
@@ -162,15 +164,16 @@ class RoomStateEventRestServlet(ClientV1RestServlet):
                 content=content,
             )
         else:
-            msg_handler = self.handlers.message_handler
-            event, context = yield msg_handler.create_event(
+            event, context = yield self.event_creation_hander.create_event(
                 requester,
                 event_dict,
                 token_id=requester.access_token_id,
                 txn_id=txn_id,
             )
 
-            yield msg_handler.send_nonmember_event(requester, event, context)
+            yield self.event_creation_hander.send_nonmember_event(
+                requester, event, context,
+            )
 
         ret = {}
         if event:
@@ -184,6 +187,7 @@ class RoomSendEventRestServlet(ClientV1RestServlet):
     def __init__(self, hs):
         super(RoomSendEventRestServlet, self).__init__(hs)
         self.handlers = hs.get_handlers()
+        self.event_creation_hander = hs.get_event_creation_handler()
 
     def register(self, http_server):
         # /rooms/$roomid/send/$event_type[/$txn_id]
@@ -205,8 +209,7 @@ class RoomSendEventRestServlet(ClientV1RestServlet):
         if 'ts' in request.args and requester.app_service:
             event_dict['origin_server_ts'] = parse_integer(request, "ts", 0)
 
-        msg_handler = self.handlers.message_handler
-        event = yield msg_handler.create_and_send_nonmember_event(
+        event = yield self.event_creation_hander.create_and_send_nonmember_event(
             requester,
             event_dict,
             txn_id=txn_id,
@@ -670,6 +673,7 @@ class RoomRedactEventRestServlet(ClientV1RestServlet):
     def __init__(self, hs):
         super(RoomRedactEventRestServlet, self).__init__(hs)
         self.handlers = hs.get_handlers()
+        self.event_creation_handler = hs.get_event_creation_handler()
 
     def register(self, http_server):
         PATTERNS = ("/rooms/(?P<room_id>[^/]*)/redact/(?P<event_id>[^/]*)")
@@ -680,8 +684,7 @@ class RoomRedactEventRestServlet(ClientV1RestServlet):
         requester = yield self.auth.get_user_by_req(request)
         content = parse_json_object_from_request(request)
 
-        msg_handler = self.handlers.message_handler
-        event = yield msg_handler.create_and_send_nonmember_event(
+        event = yield self.event_creation_handler.create_and_send_nonmember_event(
             requester,
             {
                 "type": EventTypes.Redaction,
diff --git a/synapse/rest/media/v1/media_storage.py b/synapse/rest/media/v1/media_storage.py
index e8e8b3986d..3f8d4b9c22 100644
--- a/synapse/rest/media/v1/media_storage.py
+++ b/synapse/rest/media/v1/media_storage.py
@@ -70,6 +70,12 @@ class MediaStorage(object):
             _write_file_synchronously, source, fname,
         ))
 
+        # Tell the storage providers about the new file. They'll decide
+        # if they should upload it and whether to do so synchronously
+        # or not.
+        for provider in self.storage_providers:
+            yield provider.store_file(path, file_info)
+
         defer.returnValue(fname)
 
     @contextlib.contextmanager
diff --git a/synapse/server.py b/synapse/server.py
index 3173aed1d0..fbd602d40e 100644
--- a/synapse/server.py
+++ b/synapse/server.py
@@ -55,6 +55,7 @@ from synapse.handlers.read_marker import ReadMarkerHandler
 from synapse.handlers.user_directory import UserDirectoryHandler
 from synapse.handlers.groups_local import GroupsLocalHandler
 from synapse.handlers.profile import ProfileHandler
+from synapse.handlers.message import EventCreationHandler
 from synapse.groups.groups_server import GroupsServerHandler
 from synapse.groups.attestations import GroupAttestionRenewer, GroupAttestationSigning
 from synapse.http.client import SimpleHttpClient, InsecureInterceptableContextFactory
@@ -118,6 +119,7 @@ class HomeServer(object):
         'application_service_handler',
         'device_message_handler',
         'profile_handler',
+        'event_creation_handler',
         'deactivate_account_handler',
         'set_password_handler',
         'notifier',
@@ -276,6 +278,9 @@ class HomeServer(object):
     def build_profile_handler(self):
         return ProfileHandler(self)
 
+    def build_event_creation_handler(self):
+        return EventCreationHandler(self)
+
     def build_deactivate_account_handler(self):
         return DeactivateAccountHandler(self)
 
diff --git a/synapse/state.py b/synapse/state.py
index 6c2aaa5e7a..932f602508 100644
--- a/synapse/state.py
+++ b/synapse/state.py
@@ -183,8 +183,15 @@ class StateHandler(object):
     def compute_event_context(self, event, old_state=None):
         """Build an EventContext structure for the event.
 
+        This works out what the current state should be for the event, and
+        generates a new state group if necessary.
+
         Args:
             event (synapse.events.EventBase):
+            old_state (dict|None): The state at the event if it can't be
+                calculated from existing events. This is normally only specified
+                when receiving an event from federation where we don't have the
+                prev events for, e.g. when backfilling.
         Returns:
             synapse.events.snapshot.EventContext:
         """
@@ -208,15 +215,22 @@ class StateHandler(object):
                 context.current_state_ids = {}
                 context.prev_state_ids = {}
             context.prev_state_events = []
-            context.state_group = self.store.get_next_state_group()
+
+            # We don't store state for outliers, so we don't generate a state
+            # froup for it.
+            context.state_group = None
+
             defer.returnValue(context)
 
         if old_state:
+            # We already have the state, so we don't need to calculate it.
+            # Let's just correctly fill out the context and create a
+            # new state group for it.
+
             context = EventContext()
             context.prev_state_ids = {
                 (s.type, s.state_key): s.event_id for s in old_state
             }
-            context.state_group = self.store.get_next_state_group()
 
             if event.is_state():
                 key = (event.type, event.state_key)
@@ -229,6 +243,14 @@ class StateHandler(object):
             else:
                 context.current_state_ids = context.prev_state_ids
 
+            context.state_group = yield self.store.store_state_group(
+                event.event_id,
+                event.room_id,
+                prev_group=None,
+                delta_ids=None,
+                current_state_ids=context.current_state_ids,
+            )
+
             context.prev_state_events = []
             defer.returnValue(context)
 
@@ -242,7 +264,8 @@ class StateHandler(object):
         context = EventContext()
         context.prev_state_ids = curr_state
         if event.is_state():
-            context.state_group = self.store.get_next_state_group()
+            # If this is a state event then we need to create a new state
+            # group for the state after this event.
 
             key = (event.type, event.state_key)
             if key in context.prev_state_ids:
@@ -253,23 +276,42 @@ class StateHandler(object):
             context.current_state_ids[key] = event.event_id
 
             if entry.state_group:
+                # If the state at the event has a state group assigned then
+                # we can use that as the prev group
                 context.prev_group = entry.state_group
                 context.delta_ids = {
                     key: event.event_id
                 }
             elif entry.prev_group:
+                # If the state at the event only has a prev group, then we can
+                # use that as a prev group too.
                 context.prev_group = entry.prev_group
                 context.delta_ids = dict(entry.delta_ids)
                 context.delta_ids[key] = event.event_id
+
+            context.state_group = yield self.store.store_state_group(
+                event.event_id,
+                event.room_id,
+                prev_group=context.prev_group,
+                delta_ids=context.delta_ids,
+                current_state_ids=context.current_state_ids,
+            )
         else:
+            context.current_state_ids = context.prev_state_ids
+            context.prev_group = entry.prev_group
+            context.delta_ids = entry.delta_ids
+
             if entry.state_group is None:
-                entry.state_group = self.store.get_next_state_group()
+                entry.state_group = yield self.store.store_state_group(
+                    event.event_id,
+                    event.room_id,
+                    prev_group=entry.prev_group,
+                    delta_ids=entry.delta_ids,
+                    current_state_ids=context.current_state_ids,
+                )
                 entry.state_id = entry.state_group
 
             context.state_group = entry.state_group
-            context.current_state_ids = context.prev_state_ids
-            context.prev_group = entry.prev_group
-            context.delta_ids = entry.delta_ids
 
         context.prev_state_events = []
         defer.returnValue(context)
diff --git a/synapse/storage/__init__.py b/synapse/storage/__init__.py
index d01d46338a..f8fbd02ceb 100644
--- a/synapse/storage/__init__.py
+++ b/synapse/storage/__init__.py
@@ -124,7 +124,6 @@ class DataStore(RoomMemberStore, RoomStore,
         )
 
         self._transaction_id_gen = IdGenerator(db_conn, "sent_transactions", "id")
-        self._state_groups_id_gen = IdGenerator(db_conn, "state_groups", "id")
         self._access_tokens_id_gen = IdGenerator(db_conn, "access_tokens", "id")
         self._event_reports_id_gen = IdGenerator(db_conn, "event_reports", "id")
         self._push_rule_id_gen = IdGenerator(db_conn, "push_rules", "id")
diff --git a/synapse/storage/engines/postgres.py b/synapse/storage/engines/postgres.py
index a6ae79dfad..8a0386c1a4 100644
--- a/synapse/storage/engines/postgres.py
+++ b/synapse/storage/engines/postgres.py
@@ -62,3 +62,9 @@ class PostgresEngine(object):
 
     def lock_table(self, txn, table):
         txn.execute("LOCK TABLE %s in EXCLUSIVE MODE" % (table,))
+
+    def get_next_state_group_id(self, txn):
+        """Returns an int that can be used as a new state_group ID
+        """
+        txn.execute("SELECT nextval('state_group_id_seq')")
+        return txn.fetchone()[0]
diff --git a/synapse/storage/engines/sqlite3.py b/synapse/storage/engines/sqlite3.py
index 755c9a1f07..60f0fa7fb3 100644
--- a/synapse/storage/engines/sqlite3.py
+++ b/synapse/storage/engines/sqlite3.py
@@ -16,6 +16,7 @@
 from synapse.storage.prepare_database import prepare_database
 
 import struct
+import threading
 
 
 class Sqlite3Engine(object):
@@ -24,6 +25,11 @@ class Sqlite3Engine(object):
     def __init__(self, database_module, database_config):
         self.module = database_module
 
+        # The current max state_group, or None if we haven't looked
+        # in the DB yet.
+        self._current_state_group_id = None
+        self._current_state_group_id_lock = threading.Lock()
+
     def check_database(self, txn):
         pass
 
@@ -43,6 +49,19 @@ class Sqlite3Engine(object):
     def lock_table(self, txn, table):
         return
 
+    def get_next_state_group_id(self, txn):
+        """Returns an int that can be used as a new state_group ID
+        """
+        # We do application locking here since if we're using sqlite then
+        # we are a single process synapse.
+        with self._current_state_group_id_lock:
+            if self._current_state_group_id is None:
+                txn.execute("SELECT COALESCE(max(id), 0) FROM state_groups")
+                self._current_state_group_id = txn.fetchone()[0]
+
+            self._current_state_group_id += 1
+            return self._current_state_group_id
+
 
 # Following functions taken from: https://github.com/coleifer/peewee
 
diff --git a/synapse/storage/events.py b/synapse/storage/events.py
index 3d5eb9bc02..d5bc423f18 100644
--- a/synapse/storage/events.py
+++ b/synapse/storage/events.py
@@ -739,9 +739,8 @@ class EventsStore(SQLBaseStore):
             events_and_contexts=events_and_contexts,
         )
 
-        # Insert into the state_groups, state_groups_state, and
-        # event_to_state_groups tables.
-        self._store_mult_state_groups_txn(txn, events_and_contexts)
+        # Insert into event_to_state_groups.
+        self._store_event_state_mappings_txn(txn, events_and_contexts)
 
         # _store_rejected_events_txn filters out any events which were
         # rejected, and returns the filtered list.
@@ -976,10 +975,9 @@ class EventsStore(SQLBaseStore):
                 # an outlier in the database. We now have some state at that
                 # so we need to update the state_groups table with that state.
 
-                # insert into the state_group, state_groups_state and
-                # event_to_state_groups tables.
+                # insert into event_to_state_groups.
                 try:
-                    self._store_mult_state_groups_txn(txn, ((event, context),))
+                    self._store_event_state_mappings_txn(txn, ((event, context),))
                 except Exception:
                     logger.exception("")
                     raise
@@ -2049,16 +2047,32 @@ class EventsStore(SQLBaseStore):
             )
         return self.runInteraction("get_all_new_events", get_all_new_events_txn)
 
-    def delete_old_state(self, room_id, topological_ordering):
-        return self.runInteraction(
-            "delete_old_state",
-            self._delete_old_state_txn, room_id, topological_ordering
-        )
+    def purge_history(
+        self, room_id, topological_ordering, delete_local_events,
+    ):
+        """Deletes room history before a certain point
+
+        Args:
+            room_id (str):
+
+            topological_ordering (int):
+                minimum topo ordering to preserve
 
-    def _delete_old_state_txn(self, txn, room_id, topological_ordering):
-        """Deletes old room state
+            delete_local_events (bool):
+                if True, we will delete local events as well as remote ones
+                (instead of just marking them as outliers and deleting their
+                state groups).
         """
 
+        return self.runInteraction(
+            "purge_history",
+            self._purge_history_txn, room_id, topological_ordering,
+            delete_local_events,
+        )
+
+    def _purge_history_txn(
+        self, txn, room_id, topological_ordering, delete_local_events,
+    ):
         # Tables that should be pruned:
         #     event_auth
         #     event_backward_extremities
@@ -2099,7 +2113,7 @@ class EventsStore(SQLBaseStore):
                 400, "topological_ordering is greater than forward extremeties"
             )
 
-        logger.debug("[purge] looking for events to delete")
+        logger.info("[purge] looking for events to delete")
 
         txn.execute(
             "SELECT event_id, state_key FROM events"
@@ -2111,16 +2125,16 @@ class EventsStore(SQLBaseStore):
 
         to_delete = [
             (event_id,) for event_id, state_key in event_rows
-            if state_key is None and not self.hs.is_mine_id(event_id)
+            if state_key is None and (
+                delete_local_events or not self.hs.is_mine_id(event_id)
+            )
         ]
         logger.info(
-            "[purge] found %i events before cutoff, of which %i are remote"
-            " non-state events to delete", len(event_rows), len(to_delete))
-
-        for event_id, state_key in event_rows:
-            txn.call_after(self._get_state_group_for_event.invalidate, (event_id,))
+            "[purge] found %i events before cutoff, of which %i can be deleted",
+            len(event_rows), len(to_delete),
+        )
 
-        logger.debug("[purge] Finding new backward extremities")
+        logger.info("[purge] Finding new backward extremities")
 
         # We calculate the new entries for the backward extremeties by finding
         # all events that point to events that are to be purged
@@ -2134,7 +2148,7 @@ class EventsStore(SQLBaseStore):
         )
         new_backwards_extrems = txn.fetchall()
 
-        logger.debug("[purge] replacing backward extremities: %r", new_backwards_extrems)
+        logger.info("[purge] replacing backward extremities: %r", new_backwards_extrems)
 
         txn.execute(
             "DELETE FROM event_backward_extremities WHERE room_id = ?",
@@ -2150,7 +2164,7 @@ class EventsStore(SQLBaseStore):
             ]
         )
 
-        logger.debug("[purge] finding redundant state groups")
+        logger.info("[purge] finding redundant state groups")
 
         # Get all state groups that are only referenced by events that are
         # to be deleted.
@@ -2167,15 +2181,15 @@ class EventsStore(SQLBaseStore):
         )
 
         state_rows = txn.fetchall()
-        logger.debug("[purge] found %i redundant state groups", len(state_rows))
+        logger.info("[purge] found %i redundant state groups", len(state_rows))
 
         # make a set of the redundant state groups, so that we can look them up
         # efficiently
         state_groups_to_delete = set([sg for sg, in state_rows])
 
         # Now we get all the state groups that rely on these state groups
-        logger.debug("[purge] finding state groups which depend on redundant"
-                     " state groups")
+        logger.info("[purge] finding state groups which depend on redundant"
+                    " state groups")
         remaining_state_groups = []
         for i in xrange(0, len(state_rows), 100):
             chunk = [sg for sg, in state_rows[i:i + 100]]
@@ -2200,7 +2214,7 @@ class EventsStore(SQLBaseStore):
         # Now we turn the state groups that reference to-be-deleted state
         # groups to non delta versions.
         for sg in remaining_state_groups:
-            logger.debug("[purge] de-delta-ing remaining state group %s", sg)
+            logger.info("[purge] de-delta-ing remaining state group %s", sg)
             curr_state = self._get_state_groups_from_groups_txn(
                 txn, [sg], types=None
             )
@@ -2237,7 +2251,7 @@ class EventsStore(SQLBaseStore):
                 ],
             )
 
-        logger.debug("[purge] removing redundant state groups")
+        logger.info("[purge] removing redundant state groups")
         txn.executemany(
             "DELETE FROM state_groups_state WHERE state_group = ?",
             state_rows
@@ -2247,18 +2261,15 @@ class EventsStore(SQLBaseStore):
             state_rows
         )
 
-        # Delete all non-state
-        logger.debug("[purge] removing events from event_to_state_groups")
+        logger.info("[purge] removing events from event_to_state_groups")
         txn.executemany(
             "DELETE FROM event_to_state_groups WHERE event_id = ?",
             [(event_id,) for event_id, _ in event_rows]
         )
-
-        logger.debug("[purge] updating room_depth")
-        txn.execute(
-            "UPDATE room_depth SET min_depth = ? WHERE room_id = ?",
-            (topological_ordering, room_id,)
-        )
+        for event_id, _ in event_rows:
+            txn.call_after(self._get_state_group_for_event.invalidate, (
+                event_id,
+            ))
 
         # Delete all remote non-state events
         for table in (
@@ -2276,7 +2287,8 @@ class EventsStore(SQLBaseStore):
             "event_signatures",
             "rejections",
         ):
-            logger.debug("[purge] removing remote non-state events from %s", table)
+            logger.info("[purge] removing remote non-state events from %s",
+                        table)
 
             txn.executemany(
                 "DELETE FROM %s WHERE event_id = ?" % (table,),
@@ -2284,16 +2296,30 @@ class EventsStore(SQLBaseStore):
             )
 
         # Mark all state and own events as outliers
-        logger.debug("[purge] marking remaining events as outliers")
+        logger.info("[purge] marking remaining events as outliers")
         txn.executemany(
             "UPDATE events SET outlier = ?"
             " WHERE event_id = ?",
             [
                 (True, event_id,) for event_id, state_key in event_rows
-                if state_key is not None or self.hs.is_mine_id(event_id)
+                if state_key is not None or (
+                    not delete_local_events and self.hs.is_mine_id(event_id)
+                )
             ]
         )
 
+        # synapse tries to take out an exclusive lock on room_depth whenever it
+        # persists events (because upsert), and once we run this update, we
+        # will block that for the rest of our transaction.
+        #
+        # So, let's stick it at the end so that we don't block event
+        # persistence.
+        logger.info("[purge] updating room_depth")
+        txn.execute(
+            "UPDATE room_depth SET min_depth = ? WHERE room_id = ?",
+            (topological_ordering, room_id,)
+        )
+
         logger.info("[purge] done")
 
     @defer.inlineCallbacks
diff --git a/synapse/storage/room.py b/synapse/storage/room.py
index cf2c4dae39..fff6652e05 100644
--- a/synapse/storage/room.py
+++ b/synapse/storage/room.py
@@ -16,11 +16,9 @@
 from twisted.internet import defer
 
 from synapse.api.errors import StoreError
+from synapse.storage.search import SearchStore
 from synapse.util.caches.descriptors import cached, cachedInlineCallbacks
 
-from ._base import SQLBaseStore
-from .engines import PostgresEngine, Sqlite3Engine
-
 import collections
 import logging
 import ujson as json
@@ -40,7 +38,7 @@ RatelimitOverride = collections.namedtuple(
 )
 
 
-class RoomStore(SQLBaseStore):
+class RoomStore(SearchStore):
 
     @defer.inlineCallbacks
     def store_room(self, room_id, room_creator_user_id, is_public):
@@ -263,8 +261,8 @@ class RoomStore(SQLBaseStore):
                 },
             )
 
-            self._store_event_search_txn(
-                txn, event, "content.topic", event.content["topic"]
+            self.store_event_search_txn(
+                txn, event, "content.topic", event.content["topic"],
             )
 
     def _store_room_name_txn(self, txn, event):
@@ -279,14 +277,14 @@ class RoomStore(SQLBaseStore):
                 }
             )
 
-            self._store_event_search_txn(
-                txn, event, "content.name", event.content["name"]
+            self.store_event_search_txn(
+                txn, event, "content.name", event.content["name"],
             )
 
     def _store_room_message_txn(self, txn, event):
         if hasattr(event, "content") and "body" in event.content:
-            self._store_event_search_txn(
-                txn, event, "content.body", event.content["body"]
+            self.store_event_search_txn(
+                txn, event, "content.body", event.content["body"],
             )
 
     def _store_history_visibility_txn(self, txn, event):
@@ -308,31 +306,6 @@ class RoomStore(SQLBaseStore):
                 event.content[key]
             ))
 
-    def _store_event_search_txn(self, txn, event, key, value):
-        if isinstance(self.database_engine, PostgresEngine):
-            sql = (
-                "INSERT INTO event_search"
-                " (event_id, room_id, key, vector, stream_ordering, origin_server_ts)"
-                " VALUES (?,?,?,to_tsvector('english', ?),?,?)"
-            )
-            txn.execute(
-                sql,
-                (
-                    event.event_id, event.room_id, key, value,
-                    event.internal_metadata.stream_ordering,
-                    event.origin_server_ts,
-                )
-            )
-        elif isinstance(self.database_engine, Sqlite3Engine):
-            sql = (
-                "INSERT INTO event_search (event_id, room_id, key, value)"
-                " VALUES (?,?,?,?)"
-            )
-            txn.execute(sql, (event.event_id, event.room_id, key, value,))
-        else:
-            # This should be unreachable.
-            raise Exception("Unrecognized database engine")
-
     def add_event_report(self, room_id, event_id, user_id, reason, content,
                          received_ts):
         next_id = self._event_reports_id_gen.get_next()
diff --git a/synapse/storage/schema/delta/47/state_group_seq.py b/synapse/storage/schema/delta/47/state_group_seq.py
new file mode 100644
index 0000000000..f6766501d2
--- /dev/null
+++ b/synapse/storage/schema/delta/47/state_group_seq.py
@@ -0,0 +1,37 @@
+# Copyright 2018 New Vector 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.
+
+from synapse.storage.engines import PostgresEngine
+
+
+def run_create(cur, database_engine, *args, **kwargs):
+    if isinstance(database_engine, PostgresEngine):
+        # if we already have some state groups, we want to start making new
+        # ones with a higher id.
+        cur.execute("SELECT max(id) FROM state_groups")
+        row = cur.fetchone()
+
+        if row[0] is None:
+            start_val = 1
+        else:
+            start_val = row[0] + 1
+
+        cur.execute(
+            "CREATE SEQUENCE state_group_id_seq START WITH %s",
+            (start_val, ),
+        )
+
+
+def run_upgrade(*args, **kwargs):
+    pass
diff --git a/synapse/storage/search.py b/synapse/storage/search.py
index 479b04c636..f1ac9ba0fd 100644
--- a/synapse/storage/search.py
+++ b/synapse/storage/search.py
@@ -13,19 +13,25 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
+from collections import namedtuple
+import logging
+import re
+import ujson as json
+
 from twisted.internet import defer
 
 from .background_updates import BackgroundUpdateStore
 from synapse.api.errors import SynapseError
 from synapse.storage.engines import PostgresEngine, Sqlite3Engine
 
-import logging
-import re
-import ujson as json
-
 
 logger = logging.getLogger(__name__)
 
+SearchEntry = namedtuple('SearchEntry', [
+    'key', 'value', 'event_id', 'room_id', 'stream_ordering',
+    'origin_server_ts',
+])
+
 
 class SearchStore(BackgroundUpdateStore):
 
@@ -49,16 +55,17 @@ class SearchStore(BackgroundUpdateStore):
 
     @defer.inlineCallbacks
     def _background_reindex_search(self, progress, batch_size):
+        # we work through the events table from highest stream id to lowest
         target_min_stream_id = progress["target_min_stream_id_inclusive"]
         max_stream_id = progress["max_stream_id_exclusive"]
         rows_inserted = progress.get("rows_inserted", 0)
 
-        INSERT_CLUMP_SIZE = 1000
         TYPES = ["m.room.name", "m.room.message", "m.room.topic"]
 
         def reindex_search_txn(txn):
             sql = (
-                "SELECT stream_ordering, event_id, room_id, type, content FROM events"
+                "SELECT stream_ordering, event_id, room_id, type, content, "
+                " origin_server_ts FROM events"
                 " WHERE ? <= stream_ordering AND stream_ordering < ?"
                 " AND (%s)"
                 " ORDER BY stream_ordering DESC"
@@ -67,6 +74,10 @@ class SearchStore(BackgroundUpdateStore):
 
             txn.execute(sql, (target_min_stream_id, max_stream_id, batch_size))
 
+            # we could stream straight from the results into
+            # store_search_entries_txn with a generator function, but that
+            # would mean having two cursors open on the database at once.
+            # Instead we just build a list of results.
             rows = self.cursor_to_dict(txn)
             if not rows:
                 return 0
@@ -79,6 +90,8 @@ class SearchStore(BackgroundUpdateStore):
                     event_id = row["event_id"]
                     room_id = row["room_id"]
                     etype = row["type"]
+                    stream_ordering = row["stream_ordering"]
+                    origin_server_ts = row["origin_server_ts"]
                     try:
                         content = json.loads(row["content"])
                     except Exception:
@@ -93,6 +106,8 @@ class SearchStore(BackgroundUpdateStore):
                     elif etype == "m.room.name":
                         key = "content.name"
                         value = content["name"]
+                    else:
+                        raise Exception("unexpected event type %s" % etype)
                 except (KeyError, AttributeError):
                     # If the event is missing a necessary field then
                     # skip over it.
@@ -103,25 +118,16 @@ class SearchStore(BackgroundUpdateStore):
                     # then skip over it
                     continue
 
-                event_search_rows.append((event_id, room_id, key, value))
+                event_search_rows.append(SearchEntry(
+                    key=key,
+                    value=value,
+                    event_id=event_id,
+                    room_id=room_id,
+                    stream_ordering=stream_ordering,
+                    origin_server_ts=origin_server_ts,
+                ))
 
-            if isinstance(self.database_engine, PostgresEngine):
-                sql = (
-                    "INSERT INTO event_search (event_id, room_id, key, vector)"
-                    " VALUES (?,?,?,to_tsvector('english', ?))"
-                )
-            elif isinstance(self.database_engine, Sqlite3Engine):
-                sql = (
-                    "INSERT INTO event_search (event_id, room_id, key, value)"
-                    " VALUES (?,?,?,?)"
-                )
-            else:
-                # This should be unreachable.
-                raise Exception("Unrecognized database engine")
-
-            for index in range(0, len(event_search_rows), INSERT_CLUMP_SIZE):
-                clump = event_search_rows[index:index + INSERT_CLUMP_SIZE]
-                txn.executemany(sql, clump)
+            self.store_search_entries_txn(txn, event_search_rows)
 
             progress = {
                 "target_min_stream_id_inclusive": target_min_stream_id,
@@ -242,6 +248,62 @@ class SearchStore(BackgroundUpdateStore):
 
         defer.returnValue(num_rows)
 
+    def store_event_search_txn(self, txn, event, key, value):
+        """Add event to the search table
+
+        Args:
+            txn (cursor):
+            event (EventBase):
+            key (str):
+            value (str):
+        """
+        self.store_search_entries_txn(
+            txn,
+            (SearchEntry(
+                key=key,
+                value=value,
+                event_id=event.event_id,
+                room_id=event.room_id,
+                stream_ordering=event.internal_metadata.stream_ordering,
+                origin_server_ts=event.origin_server_ts,
+            ),),
+        )
+
+    def store_search_entries_txn(self, txn, entries):
+        """Add entries to the search table
+
+        Args:
+            txn (cursor):
+            entries (iterable[SearchEntry]):
+                entries to be added to the table
+        """
+        if isinstance(self.database_engine, PostgresEngine):
+            sql = (
+                "INSERT INTO event_search"
+                " (event_id, room_id, key, vector, stream_ordering, origin_server_ts)"
+                " VALUES (?,?,?,to_tsvector('english', ?),?,?)"
+            )
+
+            args = ((
+                entry.event_id, entry.room_id, entry.key, entry.value,
+                entry.stream_ordering, entry.origin_server_ts,
+            ) for entry in entries)
+
+            txn.executemany(sql, args)
+        elif isinstance(self.database_engine, Sqlite3Engine):
+            sql = (
+                "INSERT INTO event_search (event_id, room_id, key, value)"
+                " VALUES (?,?,?,?)"
+            )
+            args = ((
+                entry.event_id, entry.room_id, entry.key, entry.value,
+            ) for entry in entries)
+
+            txn.executemany(sql, args)
+        else:
+            # This should be unreachable.
+            raise Exception("Unrecognized database engine")
+
     @defer.inlineCallbacks
     def search_msgs(self, room_ids, search_term, keys):
         """Performs a full text search over events with given keys.
diff --git a/synapse/storage/state.py b/synapse/storage/state.py
index 360e3e4355..adb48df73e 100644
--- a/synapse/storage/state.py
+++ b/synapse/storage/state.py
@@ -42,11 +42,8 @@ class _GetStateGroupDelta(namedtuple("_GetStateGroupDelta", ("prev_group", "delt
         return len(self.delta_ids) if self.delta_ids else 0
 
 
-class StateGroupReadStore(SQLBaseStore):
-    """The read-only parts of StateGroupStore
-
-    None of these functions write to the state tables, so are suitable for
-    including in the SlavedStores.
+class StateGroupWorkerStore(SQLBaseStore):
+    """The parts of StateGroupStore that can be called from workers.
     """
 
     STATE_GROUP_DEDUPLICATION_UPDATE_NAME = "state_group_state_deduplication"
@@ -54,7 +51,7 @@ class StateGroupReadStore(SQLBaseStore):
     CURRENT_STATE_INDEX_UPDATE_NAME = "current_state_members_idx"
 
     def __init__(self, db_conn, hs):
-        super(StateGroupReadStore, self).__init__(db_conn, hs)
+        super(StateGroupWorkerStore, self).__init__(db_conn, hs)
 
         self._state_group_cache = DictionaryCache(
             "*stateGroupCache*", 100000 * CACHE_SIZE_FACTOR
@@ -549,116 +546,66 @@ class StateGroupReadStore(SQLBaseStore):
 
         defer.returnValue(results)
 
+    def store_state_group(self, event_id, room_id, prev_group, delta_ids,
+                          current_state_ids):
+        """Store a new set of state, returning a newly assigned state group.
 
-class StateStore(StateGroupReadStore, BackgroundUpdateStore):
-    """ Keeps track of the state at a given event.
-
-    This is done by the concept of `state groups`. Every event is a assigned
-    a state group (identified by an arbitrary string), which references a
-    collection of state events. The current state of an event is then the
-    collection of state events referenced by the event's state group.
-
-    Hence, every change in the current state causes a new state group to be
-    generated. However, if no change happens (e.g., if we get a message event
-    with only one parent it inherits the state group from its parent.)
-
-    There are three tables:
-      * `state_groups`: Stores group name, first event with in the group and
-        room id.
-      * `event_to_state_groups`: Maps events to state groups.
-      * `state_groups_state`: Maps state group to state events.
-    """
-
-    STATE_GROUP_DEDUPLICATION_UPDATE_NAME = "state_group_state_deduplication"
-    STATE_GROUP_INDEX_UPDATE_NAME = "state_group_state_type_index"
-    CURRENT_STATE_INDEX_UPDATE_NAME = "current_state_members_idx"
-
-    def __init__(self, db_conn, hs):
-        super(StateStore, self).__init__(db_conn, hs)
-        self.register_background_update_handler(
-            self.STATE_GROUP_DEDUPLICATION_UPDATE_NAME,
-            self._background_deduplicate_state,
-        )
-        self.register_background_update_handler(
-            self.STATE_GROUP_INDEX_UPDATE_NAME,
-            self._background_index_state,
-        )
-        self.register_background_index_update(
-            self.CURRENT_STATE_INDEX_UPDATE_NAME,
-            index_name="current_state_events_member_index",
-            table="current_state_events",
-            columns=["state_key"],
-            where_clause="type='m.room.member'",
-        )
-
-    def _have_persisted_state_group_txn(self, txn, state_group):
-        txn.execute(
-            "SELECT count(*) FROM state_groups WHERE id = ?",
-            (state_group,)
-        )
-        row = txn.fetchone()
-        return row and row[0]
-
-    def _store_mult_state_groups_txn(self, txn, events_and_contexts):
-        state_groups = {}
-        for event, context in events_and_contexts:
-            if event.internal_metadata.is_outlier():
-                continue
+        Args:
+            event_id (str): The event ID for which the state was calculated
+            room_id (str)
+            prev_group (int|None): A previous state group for the room, optional.
+            delta_ids (dict|None): The delta between state at `prev_group` and
+                `current_state_ids`, if `prev_group` was given. Same format as
+                `current_state_ids`.
+            current_state_ids (dict): The state to store. Map of (type, state_key)
+                to event_id.
 
-            if context.current_state_ids is None:
+        Returns:
+            Deferred[int]: The state group ID
+        """
+        def _store_state_group_txn(txn):
+            if current_state_ids is None:
                 # AFAIK, this can never happen
-                logger.error(
-                    "Non-outlier event %s had current_state_ids==None",
-                    event.event_id)
-                continue
+                raise Exception("current_state_ids cannot be None")
 
-            # if the event was rejected, just give it the same state as its
-            # predecessor.
-            if context.rejected:
-                state_groups[event.event_id] = context.prev_group
-                continue
-
-            state_groups[event.event_id] = context.state_group
-
-            if self._have_persisted_state_group_txn(txn, context.state_group):
-                continue
+            state_group = self.database_engine.get_next_state_group_id(txn)
 
             self._simple_insert_txn(
                 txn,
                 table="state_groups",
                 values={
-                    "id": context.state_group,
-                    "room_id": event.room_id,
-                    "event_id": event.event_id,
+                    "id": state_group,
+                    "room_id": room_id,
+                    "event_id": event_id,
                 },
             )
 
             # We persist as a delta if we can, while also ensuring the chain
             # of deltas isn't tooo long, as otherwise read performance degrades.
-            if context.prev_group:
+            if prev_group:
                 is_in_db = self._simple_select_one_onecol_txn(
                     txn,
                     table="state_groups",
-                    keyvalues={"id": context.prev_group},
+                    keyvalues={"id": prev_group},
                     retcol="id",
                     allow_none=True,
                 )
                 if not is_in_db:
                     raise Exception(
                         "Trying to persist state with unpersisted prev_group: %r"
-                        % (context.prev_group,)
+                        % (prev_group,)
                     )
 
                 potential_hops = self._count_state_group_hops_txn(
-                    txn, context.prev_group
+                    txn, prev_group
                 )
-            if context.prev_group and potential_hops < MAX_STATE_DELTA_HOPS:
+            if prev_group and potential_hops < MAX_STATE_DELTA_HOPS:
                 self._simple_insert_txn(
                     txn,
                     table="state_group_edges",
                     values={
-                        "state_group": context.state_group,
-                        "prev_state_group": context.prev_group,
+                        "state_group": state_group,
+                        "prev_state_group": prev_group,
                     },
                 )
 
@@ -667,13 +614,13 @@ class StateStore(StateGroupReadStore, BackgroundUpdateStore):
                     table="state_groups_state",
                     values=[
                         {
-                            "state_group": context.state_group,
-                            "room_id": event.room_id,
+                            "state_group": state_group,
+                            "room_id": room_id,
                             "type": key[0],
                             "state_key": key[1],
                             "event_id": state_id,
                         }
-                        for key, state_id in context.delta_ids.iteritems()
+                        for key, state_id in delta_ids.iteritems()
                     ],
                 )
             else:
@@ -682,13 +629,13 @@ class StateStore(StateGroupReadStore, BackgroundUpdateStore):
                     table="state_groups_state",
                     values=[
                         {
-                            "state_group": context.state_group,
-                            "room_id": event.room_id,
+                            "state_group": state_group,
+                            "room_id": room_id,
                             "type": key[0],
                             "state_key": key[1],
                             "event_id": state_id,
                         }
-                        for key, state_id in context.current_state_ids.iteritems()
+                        for key, state_id in current_state_ids.iteritems()
                     ],
                 )
 
@@ -699,11 +646,71 @@ class StateStore(StateGroupReadStore, BackgroundUpdateStore):
             txn.call_after(
                 self._state_group_cache.update,
                 self._state_group_cache.sequence,
-                key=context.state_group,
-                value=dict(context.current_state_ids),
+                key=state_group,
+                value=dict(current_state_ids),
                 full=True,
             )
 
+            return state_group
+
+        return self.runInteraction("store_state_group", _store_state_group_txn)
+
+
+class StateStore(StateGroupWorkerStore, BackgroundUpdateStore):
+    """ Keeps track of the state at a given event.
+
+    This is done by the concept of `state groups`. Every event is a assigned
+    a state group (identified by an arbitrary string), which references a
+    collection of state events. The current state of an event is then the
+    collection of state events referenced by the event's state group.
+
+    Hence, every change in the current state causes a new state group to be
+    generated. However, if no change happens (e.g., if we get a message event
+    with only one parent it inherits the state group from its parent.)
+
+    There are three tables:
+      * `state_groups`: Stores group name, first event with in the group and
+        room id.
+      * `event_to_state_groups`: Maps events to state groups.
+      * `state_groups_state`: Maps state group to state events.
+    """
+
+    STATE_GROUP_DEDUPLICATION_UPDATE_NAME = "state_group_state_deduplication"
+    STATE_GROUP_INDEX_UPDATE_NAME = "state_group_state_type_index"
+    CURRENT_STATE_INDEX_UPDATE_NAME = "current_state_members_idx"
+
+    def __init__(self, db_conn, hs):
+        super(StateStore, self).__init__(db_conn, hs)
+        self.register_background_update_handler(
+            self.STATE_GROUP_DEDUPLICATION_UPDATE_NAME,
+            self._background_deduplicate_state,
+        )
+        self.register_background_update_handler(
+            self.STATE_GROUP_INDEX_UPDATE_NAME,
+            self._background_index_state,
+        )
+        self.register_background_index_update(
+            self.CURRENT_STATE_INDEX_UPDATE_NAME,
+            index_name="current_state_events_member_index",
+            table="current_state_events",
+            columns=["state_key"],
+            where_clause="type='m.room.member'",
+        )
+
+    def _store_event_state_mappings_txn(self, txn, events_and_contexts):
+        state_groups = {}
+        for event, context in events_and_contexts:
+            if event.internal_metadata.is_outlier():
+                continue
+
+            # if the event was rejected, just give it the same state as its
+            # predecessor.
+            if context.rejected:
+                state_groups[event.event_id] = context.prev_group
+                continue
+
+            state_groups[event.event_id] = context.state_group
+
         self._simple_insert_many_txn(
             txn,
             table="event_to_state_groups",
@@ -763,9 +770,6 @@ class StateStore(StateGroupReadStore, BackgroundUpdateStore):
 
             return count
 
-    def get_next_state_group(self):
-        return self._state_groups_id_gen.get_next()
-
     @defer.inlineCallbacks
     def _background_deduplicate_state(self, progress, batch_size):
         """This background update will slowly deduplicate state by reencoding