Merge branch 'develop' of github.com:matrix-org/synapse into erikj/dns_cache

8 files changed, 951 insertions, 823 deletions

diff --git a/synapse/handlers/__init__.py b/synapse/handlers/__init__.py
index 66d2c01123..f4dbf47c1d 100644
--- a/synapse/handlers/__init__.py
+++ b/synapse/handlers/__init__.py
@@ -17,8 +17,9 @@ from synapse.appservice.scheduler import AppServiceScheduler
 from synapse.appservice.api import ApplicationServiceApi
 from .register import RegistrationHandler
 from .room import (
-    RoomCreationHandler, RoomMemberHandler, RoomListHandler, RoomContextHandler,
+    RoomCreationHandler, RoomListHandler, RoomContextHandler,
 )
+from .room_member import RoomMemberHandler
 from .message import MessageHandler
 from .events import EventStreamHandler, EventHandler
 from .federation import FederationHandler
diff --git a/synapse/handlers/_base.py b/synapse/handlers/_base.py
index 90eabb6eb7..88d8b9ba54 100644
--- a/synapse/handlers/_base.py
+++ b/synapse/handlers/_base.py
@@ -37,12 +37,22 @@ VISIBILITY_PRIORITY = (
 )
 
 
+MEMBERSHIP_PRIORITY = (
+    Membership.JOIN,
+    Membership.INVITE,
+    Membership.KNOCK,
+    Membership.LEAVE,
+    Membership.BAN,
+)
+
+
 class BaseHandler(object):
     """
     Common base class for the event handlers.
 
-    :type store: synapse.storage.events.StateStore
-    :type state_handler: synapse.state.StateHandler
+    Attributes:
+        store (synapse.storage.events.StateStore):
+        state_handler (synapse.state.StateHandler):
     """
 
     def __init__(self, hs):
@@ -65,11 +75,13 @@ class BaseHandler(object):
         """ Returns dict of user_id -> list of events that user is allowed to
         see.
 
-        :param (str, bool) user_tuples: (user id, is_peeking) for each
-            user to be checked. is_peeking should be true if:
-              * the user is not currently a member of the room, and:
-              * the user has not been a member of the room since the given
-                events
+        Args:
+            user_tuples (str, bool): (user id, is_peeking) for each user to be
+                checked. is_peeking should be true if:
+                * the user is not currently a member of the room, and:
+                * the user has not been a member of the room since the
+                given events
+            events ([synapse.events.EventBase]): list of events to filter
         """
         forgotten = yield defer.gatherResults([
             self.store.who_forgot_in_room(
@@ -84,6 +96,12 @@ class BaseHandler(object):
         )
 
         def allowed(event, user_id, is_peeking):
+            """
+            Args:
+                event (synapse.events.EventBase): event to check
+                user_id (str)
+                is_peeking (bool)
+            """
             state = event_id_to_state[event.event_id]
 
             # get the room_visibility at the time of the event.
@@ -115,17 +133,30 @@ class BaseHandler(object):
                 if old_priority < new_priority:
                     visibility = prev_visibility
 
-            # get the user's membership at the time of the event. (or rather,
-            # just *after* the event. Which means that people can see their
-            # own join events, but not (currently) their own leave events.)
-            membership_event = state.get((EventTypes.Member, user_id), None)
-            if membership_event:
-                if membership_event.event_id in event_id_forgotten:
-                    membership = None
-                else:
-                    membership = membership_event.membership
-            else:
-                membership = None
+            # likewise, if the event is the user's own membership event, use
+            # the 'most joined' membership
+            membership = None
+            if event.type == EventTypes.Member and event.state_key == user_id:
+                membership = event.content.get("membership", None)
+                if membership not in MEMBERSHIP_PRIORITY:
+                    membership = "leave"
+
+                prev_content = event.unsigned.get("prev_content", {})
+                prev_membership = prev_content.get("membership", None)
+                if prev_membership not in MEMBERSHIP_PRIORITY:
+                    prev_membership = "leave"
+
+                new_priority = MEMBERSHIP_PRIORITY.index(membership)
+                old_priority = MEMBERSHIP_PRIORITY.index(prev_membership)
+                if old_priority < new_priority:
+                    membership = prev_membership
+
+            # otherwise, get the user's membership at the time of the event.
+            if membership is None:
+                membership_event = state.get((EventTypes.Member, user_id), None)
+                if membership_event:
+                    if membership_event.event_id not in event_id_forgotten:
+                        membership = membership_event.membership
 
             # if the user was a member of the room at the time of the event,
             # they can see it.
@@ -165,13 +196,16 @@ class BaseHandler(object):
         """
         Check which events a user is allowed to see
 
-        :param str user_id: user id to be checked
-        :param [synapse.events.EventBase] events: list of events to be checked
-        :param bool is_peeking should be True if:
+        Args:
+            user_id(str): user id to be checked
+            events([synapse.events.EventBase]): list of events to be checked
+            is_peeking(bool): should be True if:
               * the user is not currently a member of the room, and:
               * the user has not been a member of the room since the given
                 events
-        :rtype [synapse.events.EventBase]
+
+        Returns:
+            [synapse.events.EventBase]
         """
         types = (
             (EventTypes.RoomHistoryVisibility, ""),
@@ -199,20 +233,25 @@ class BaseHandler(object):
             )
 
     @defer.inlineCallbacks
-    def _create_new_client_event(self, builder):
-        latest_ret = yield self.store.get_latest_event_ids_and_hashes_in_room(
-            builder.room_id,
-        )
-
-        if latest_ret:
-            depth = max([d for _, _, d in latest_ret]) + 1
+    def _create_new_client_event(self, builder, 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)
+            depth = prev_max_depth + 1
         else:
-            depth = 1
+            latest_ret = yield self.store.get_latest_event_ids_and_hashes_in_room(
+                builder.room_id,
+            )
 
-        prev_events = [
-            (event_id, prev_hashes)
-            for event_id, prev_hashes, _ in latest_ret
-        ]
+            if latest_ret:
+                depth = max([d for _, _, d in latest_ret]) + 1
+            else:
+                depth = 1
+
+            prev_events = [
+                (event_id, prev_hashes)
+                for event_id, prev_hashes, _ in latest_ret
+            ]
 
         builder.prev_events = prev_events
         builder.depth = depth
@@ -221,50 +260,6 @@ class BaseHandler(object):
 
         context = yield state_handler.compute_event_context(builder)
 
-        # If we've received an invite over federation, there are no latest
-        # events in the room, because we don't know enough about the graph
-        # fragment we received to treat it like a graph, so the above returned
-        # no relevant events. It may have returned some events (if we have
-        # joined and left the room), but not useful ones, like the invite.
-        if (
-            not self.is_host_in_room(context.current_state) and
-            builder.type == EventTypes.Member
-        ):
-            prev_member_event = yield self.store.get_room_member(
-                builder.sender, builder.room_id
-            )
-
-            # The prev_member_event may already be in context.current_state,
-            # despite us not being present in the room; in particular, if
-            # inviting user, and all other local users, have already left.
-            #
-            # In that case, we have all the information we need, and we don't
-            # want to drop "context" - not least because we may need to handle
-            # the invite locally, which will require us to have the whole
-            # context (not just prev_member_event) to auth it.
-            #
-            context_event_ids = (
-                e.event_id for e in context.current_state.values()
-            )
-
-            if (
-                prev_member_event and
-                prev_member_event.event_id not in context_event_ids
-            ):
-                # The prev_member_event is missing from context, so it must
-                # have arrived over federation and is an outlier. We forcibly
-                # set our context to the invite we received over federation
-                builder.prev_events = (
-                    prev_member_event.event_id,
-                    prev_member_event.prev_events
-                )
-
-                context = yield state_handler.compute_event_context(
-                    builder,
-                    old_state=(prev_member_event,),
-                    outlier=True
-                )
-
         if builder.is_state():
             builder.prev_state = yield self.store.add_event_hashes(
                 context.prev_state_events
diff --git a/synapse/handlers/auth.py b/synapse/handlers/auth.py
index 82d458b424..d5d6faa85f 100644
--- a/synapse/handlers/auth.py
+++ b/synapse/handlers/auth.py
@@ -163,9 +163,13 @@ class AuthHandler(BaseHandler):
     def get_session_id(self, clientdict):
         """
         Gets the session ID for a client given the client dictionary
-        :param clientdict: The dictionary sent by the client in the request
-        :return: The string session ID the client sent. If the client did not
-                 send a session ID, returns None.
+
+        Args:
+            clientdict: The dictionary sent by the client in the request
+
+        Returns:
+            str|None: The string session ID the client sent. If the client did
+                not send a session ID, returns None.
         """
         sid = None
         if clientdict and 'auth' in clientdict:
@@ -179,9 +183,11 @@ class AuthHandler(BaseHandler):
         Store a key-value pair into the sessions data associated with this
         request. This data is stored server-side and cannot be modified by
         the client.
-        :param session_id: (string) The ID of this session as returned from check_auth
-        :param key: (string) The key to store the data under
-        :param value: (any) The data to store
+
+        Args:
+            session_id (string): The ID of this session as returned from check_auth
+            key (string): The key to store the data under
+            value (any): The data to store
         """
         sess = self._get_session_info(session_id)
         sess.setdefault('serverdict', {})[key] = value
@@ -190,9 +196,11 @@ class AuthHandler(BaseHandler):
     def get_session_data(self, session_id, key, default=None):
         """
         Retrieve data stored with set_session_data
-        :param session_id: (string) The ID of this session as returned from check_auth
-        :param key: (string) The key to store the data under
-        :param default: (any) Value to return if the key has not been set
+
+        Args:
+            session_id (string): The ID of this session as returned from check_auth
+            key (string): The key to store the data under
+            default (any): Value to return if the key has not been set
         """
         sess = self._get_session_info(session_id)
         return sess.setdefault('serverdict', {}).get(key, default)
diff --git a/synapse/handlers/federation.py b/synapse/handlers/federation.py
index 267fedf114..eb02f0e000 100644
--- a/synapse/handlers/federation.py
+++ b/synapse/handlers/federation.py
@@ -102,8 +102,7 @@ class FederationHandler(BaseHandler):
 
     @log_function
     @defer.inlineCallbacks
-    def on_receive_pdu(self, origin, pdu, state=None,
-                       auth_chain=None):
+    def on_receive_pdu(self, origin, pdu, state=None, auth_chain=None):
         """ Called by the ReplicationLayer when we have a new pdu. We need to
         do auth checks and put it through the StateHandler.
         """
@@ -174,11 +173,7 @@ class FederationHandler(BaseHandler):
                     })
                     seen_ids.add(e.event_id)
 
-                yield self._handle_new_events(
-                    origin,
-                    event_infos,
-                    outliers=True
-                )
+                yield self._handle_new_events(origin, event_infos)
 
             try:
                 context, event_stream_id, max_stream_id = yield self._handle_new_event(
@@ -289,6 +284,9 @@ class FederationHandler(BaseHandler):
     def backfill(self, dest, room_id, limit, extremities=[]):
         """ Trigger a backfill request to `dest` for the given `room_id`
         """
+        if dest == self.server_name:
+            raise SynapseError(400, "Can't backfill from self.")
+
         if not extremities:
             extremities = yield self.store.get_oldest_events_in_room(room_id)
 
@@ -455,7 +453,7 @@ class FederationHandler(BaseHandler):
 
         likely_domains = [
             domain for domain, depth in curr_domains
-            if domain is not self.server_name
+            if domain != self.server_name
         ]
 
         @defer.inlineCallbacks
@@ -761,6 +759,7 @@ class FederationHandler(BaseHandler):
         event = pdu
 
         event.internal_metadata.outlier = True
+        event.internal_metadata.invite_from_remote = True
 
         event.signatures.update(
             compute_event_signature(
@@ -788,13 +787,19 @@ class FederationHandler(BaseHandler):
 
     @defer.inlineCallbacks
     def do_remotely_reject_invite(self, target_hosts, room_id, user_id):
-        origin, event = yield self._make_and_verify_event(
-            target_hosts,
-            room_id,
-            user_id,
-            "leave"
-        )
-        signed_event = self._sign_event(event)
+        try:
+            origin, event = yield self._make_and_verify_event(
+                target_hosts,
+                room_id,
+                user_id,
+                "leave"
+            )
+            signed_event = self._sign_event(event)
+        except SynapseError:
+            raise
+        except CodeMessageException as e:
+            logger.warn("Failed to reject invite: %s", e)
+            raise SynapseError(500, "Failed to reject invite")
 
         # Try the host we successfully got a response to /make_join/
         # request first.
@@ -804,10 +809,16 @@ class FederationHandler(BaseHandler):
         except ValueError:
             pass
 
-        yield self.replication_layer.send_leave(
-            target_hosts,
-            signed_event
-        )
+        try:
+            yield self.replication_layer.send_leave(
+                target_hosts,
+                signed_event
+            )
+        except SynapseError:
+            raise
+        except CodeMessageException as e:
+            logger.warn("Failed to reject invite: %s", e)
+            raise SynapseError(500, "Failed to reject invite")
 
         context = yield self.state_handler.compute_event_context(event)
 
@@ -1069,9 +1080,6 @@ class FederationHandler(BaseHandler):
     @defer.inlineCallbacks
     @log_function
     def _handle_new_event(self, origin, event, state=None, auth_events=None):
-
-        outlier = event.internal_metadata.is_outlier()
-
         context = yield self._prep_event(
             origin, event,
             state=state,
@@ -1087,14 +1095,12 @@ class FederationHandler(BaseHandler):
         event_stream_id, max_stream_id = yield self.store.persist_event(
             event,
             context=context,
-            is_new_state=not outlier,
         )
 
         defer.returnValue((context, event_stream_id, max_stream_id))
 
     @defer.inlineCallbacks
-    def _handle_new_events(self, origin, event_infos, backfilled=False,
-                           outliers=False):
+    def _handle_new_events(self, origin, event_infos, backfilled=False):
         contexts = yield defer.gatherResults(
             [
                 self._prep_event(
@@ -1113,7 +1119,6 @@ class FederationHandler(BaseHandler):
                 for ev_info, context in itertools.izip(event_infos, contexts)
             ],
             backfilled=backfilled,
-            is_new_state=(not outliers and not backfilled),
         )
 
     @defer.inlineCallbacks
@@ -1128,11 +1133,9 @@ class FederationHandler(BaseHandler):
         """
         events_to_context = {}
         for e in itertools.chain(auth_events, state):
-            ctx = yield self.state_handler.compute_event_context(
-                e, outlier=True,
-            )
-            events_to_context[e.event_id] = ctx
             e.internal_metadata.outlier = True
+            ctx = yield self.state_handler.compute_event_context(e)
+            events_to_context[e.event_id] = ctx
 
         event_map = {
             e.event_id: e
@@ -1176,16 +1179,14 @@ class FederationHandler(BaseHandler):
                 (e, events_to_context[e.event_id])
                 for e in itertools.chain(auth_events, state)
             ],
-            is_new_state=False,
         )
 
         new_event_context = yield self.state_handler.compute_event_context(
-            event, old_state=state, outlier=False,
+            event, old_state=state
         )
 
         event_stream_id, max_stream_id = yield self.store.persist_event(
             event, new_event_context,
-            is_new_state=True,
             current_state=state,
         )
 
@@ -1193,10 +1194,9 @@ class FederationHandler(BaseHandler):
 
     @defer.inlineCallbacks
     def _prep_event(self, origin, event, state=None, auth_events=None):
-        outlier = event.internal_metadata.is_outlier()
 
         context = yield self.state_handler.compute_event_context(
-            event, old_state=state, outlier=outlier,
+            event, old_state=state,
         )
 
         if not auth_events:
@@ -1718,13 +1718,15 @@ class FederationHandler(BaseHandler):
     def _check_signature(self, event, auth_events):
         """
         Checks that the signature in the event is consistent with its invite.
-        :param event (Event): The m.room.member event to check
-        :param auth_events (dict<(event type, state_key), event>)
 
-        :raises
-            AuthError if signature didn't match any keys, or key has been
+        Args:
+            event (Event): The m.room.member event to check
+            auth_events (dict<(event type, state_key), event>):
+
+        Raises:
+            AuthError: if signature didn't match any keys, or key has been
                 revoked,
-            SynapseError if a transient error meant a key couldn't be checked
+            SynapseError: if a transient error meant a key couldn't be checked
                 for revocation.
         """
         signed = event.content["third_party_invite"]["signed"]
@@ -1766,12 +1768,13 @@ class FederationHandler(BaseHandler):
         """
         Checks whether public_key has been revoked.
 
-        :param public_key (str): base-64 encoded public key.
-        :param url (str): Key revocation URL.
+        Args:
+            public_key (str): base-64 encoded public key.
+            url (str): Key revocation URL.
 
-        :raises
-            AuthError if they key has been revoked.
-            SynapseError if a transient error meant a key couldn't be checked
+        Raises:
+            AuthError: if they key has been revoked.
+            SynapseError: if a transient error meant a key couldn't be checked
                 for revocation.
         """
         try:
diff --git a/synapse/handlers/message.py b/synapse/handlers/message.py
index 5c50c611ba..10608c0dd9 100644
--- a/synapse/handlers/message.py
+++ b/synapse/handlers/message.py
@@ -21,6 +21,7 @@ from synapse.streams.config import PaginationConfig
 from synapse.events.utils import serialize_event
 from synapse.events.validator import EventValidator
 from synapse.util import unwrapFirstError
+from synapse.util.async import concurrently_execute
 from synapse.util.caches.snapshot_cache import SnapshotCache
 from synapse.types import UserID, RoomStreamToken, StreamToken
 
@@ -175,7 +176,7 @@ class MessageHandler(BaseHandler):
         defer.returnValue(chunk)
 
     @defer.inlineCallbacks
-    def create_event(self, event_dict, token_id=None, txn_id=None):
+    def create_event(self, event_dict, token_id=None, txn_id=None, prev_event_ids=None):
         """
         Given a dict from a client, create a new event.
 
@@ -186,6 +187,9 @@ class MessageHandler(BaseHandler):
 
         Args:
             event_dict (dict): An entire event
+            token_id (str)
+            txn_id (str)
+            prev_event_ids (list): The prev event ids to use when creating the event
 
         Returns:
             Tuple of created event (FrozenEvent), Context
@@ -224,6 +228,7 @@ class MessageHandler(BaseHandler):
 
         event, context = yield self._create_new_client_event(
             builder=builder,
+            prev_event_ids=prev_event_ids,
         )
         defer.returnValue((event, context))
 
@@ -556,14 +561,7 @@ class MessageHandler(BaseHandler):
             except:
                 logger.exception("Failed to get snapshot")
 
-        # Only do N rooms at once
-        n = 5
-        d_list = [handle_room(e) for e in room_list]
-        for i in range(0, len(d_list), n):
-            yield defer.gatherResults(
-                d_list[i:i + n],
-                consumeErrors=True
-            ).addErrback(unwrapFirstError)
+        yield concurrently_execute(handle_room, room_list, 10)
 
         account_data_events = []
         for account_data_type, content in account_data.items():
diff --git a/synapse/handlers/room.py b/synapse/handlers/room.py
index 71f7ab3d22..3e1d9282d7 100644
--- a/synapse/handlers/room.py
+++ b/synapse/handlers/room.py
@@ -18,20 +18,17 @@ from twisted.internet import defer
 
 from ._base import BaseHandler
 
-from synapse.types import UserID, RoomAlias, RoomID, RoomStreamToken, Requester
+from synapse.types import UserID, RoomAlias, RoomID, RoomStreamToken
 from synapse.api.constants import (
-    EventTypes, Membership, JoinRules, RoomCreationPreset,
+    EventTypes, JoinRules, RoomCreationPreset,
 )
-from synapse.api.errors import AuthError, StoreError, SynapseError, Codes
-from synapse.util import stringutils, unwrapFirstError
+from synapse.api.errors import AuthError, StoreError, SynapseError
+from synapse.util import stringutils
+from synapse.util.async import concurrently_execute
 from synapse.util.logcontext import preserve_context_over_fn
 from synapse.util.caches.response_cache import ResponseCache
 
-from signedjson.sign import verify_signed_json
-from signedjson.key import decode_verify_key_bytes
-
 from collections import OrderedDict
-from unpaddedbase64 import decode_base64
 
 import logging
 import math
@@ -357,599 +354,6 @@ class RoomCreationHandler(BaseHandler):
             )
 
 
-class RoomMemberHandler(BaseHandler):
-    # TODO(paul): This handler currently contains a messy conflation of
-    #   low-level API that works on UserID objects and so on, and REST-level
-    #   API that takes ID strings and returns pagination chunks. These concerns
-    #   ought to be separated out a lot better.
-
-    def __init__(self, hs):
-        super(RoomMemberHandler, self).__init__(hs)
-
-        self.clock = hs.get_clock()
-
-        self.distributor = hs.get_distributor()
-        self.distributor.declare("user_joined_room")
-        self.distributor.declare("user_left_room")
-
-    @defer.inlineCallbacks
-    def get_room_members(self, room_id):
-        users = yield self.store.get_users_in_room(room_id)
-
-        defer.returnValue([UserID.from_string(u) for u in users])
-
-    @defer.inlineCallbacks
-    def fetch_room_distributions_into(self, room_id, localusers=None,
-                                      remotedomains=None, ignore_user=None):
-        """Fetch the distribution of a room, adding elements to either
-        'localusers' or 'remotedomains', which should be a set() if supplied.
-        If ignore_user is set, ignore that user.
-
-        This function returns nothing; its result is performed by the
-        side-effect on the two passed sets. This allows easy accumulation of
-        member lists of multiple rooms at once if required.
-        """
-        members = yield self.get_room_members(room_id)
-        for member in members:
-            if ignore_user is not None and member == ignore_user:
-                continue
-
-            if self.hs.is_mine(member):
-                if localusers is not None:
-                    localusers.add(member)
-            else:
-                if remotedomains is not None:
-                    remotedomains.add(member.domain)
-
-    @defer.inlineCallbacks
-    def update_membership(
-            self,
-            requester,
-            target,
-            room_id,
-            action,
-            txn_id=None,
-            remote_room_hosts=None,
-            third_party_signed=None,
-            ratelimit=True,
-    ):
-        effective_membership_state = action
-        if action in ["kick", "unban"]:
-            effective_membership_state = "leave"
-
-        if third_party_signed is not None:
-            replication = self.hs.get_replication_layer()
-            yield replication.exchange_third_party_invite(
-                third_party_signed["sender"],
-                target.to_string(),
-                room_id,
-                third_party_signed,
-            )
-
-        msg_handler = self.hs.get_handlers().message_handler
-
-        content = {"membership": effective_membership_state}
-        if requester.is_guest:
-            content["kind"] = "guest"
-
-        event, context = yield msg_handler.create_event(
-            {
-                "type": EventTypes.Member,
-                "content": content,
-                "room_id": room_id,
-                "sender": requester.user.to_string(),
-                "state_key": target.to_string(),
-
-                # For backwards compatibility:
-                "membership": effective_membership_state,
-            },
-            token_id=requester.access_token_id,
-            txn_id=txn_id,
-        )
-
-        old_state = context.current_state.get((EventTypes.Member, event.state_key))
-        old_membership = old_state.content.get("membership") if old_state else None
-        if action == "unban" and old_membership != "ban":
-            raise SynapseError(
-                403,
-                "Cannot unban user who was not banned (membership=%s)" % old_membership,
-                errcode=Codes.BAD_STATE
-            )
-        if old_membership == "ban" and action != "unban":
-            raise SynapseError(
-                403,
-                "Cannot %s user who was is banned" % (action,),
-                errcode=Codes.BAD_STATE
-            )
-
-        member_handler = self.hs.get_handlers().room_member_handler
-        yield member_handler.send_membership_event(
-            requester,
-            event,
-            context,
-            ratelimit=ratelimit,
-            remote_room_hosts=remote_room_hosts,
-        )
-
-    @defer.inlineCallbacks
-    def send_membership_event(
-            self,
-            requester,
-            event,
-            context,
-            remote_room_hosts=None,
-            ratelimit=True,
-    ):
-        """
-        Change the membership status of a user in a room.
-
-        Args:
-            requester (Requester): The local user who requested the membership
-                event. If None, certain checks, like whether this homeserver can
-                act as the sender, will be skipped.
-            event (SynapseEvent): The membership event.
-            context: The context of the event.
-            is_guest (bool): Whether the sender is a guest.
-            room_hosts ([str]): Homeservers which are likely to already be in
-                the room, and could be danced with in order to join this
-                homeserver for the first time.
-            ratelimit (bool): Whether to rate limit this request.
-        Raises:
-            SynapseError if there was a problem changing the membership.
-        """
-        remote_room_hosts = remote_room_hosts or []
-
-        target_user = UserID.from_string(event.state_key)
-        room_id = event.room_id
-
-        if requester is not None:
-            sender = UserID.from_string(event.sender)
-            assert sender == requester.user, (
-                "Sender (%s) must be same as requester (%s)" %
-                (sender, requester.user)
-            )
-            assert self.hs.is_mine(sender), "Sender must be our own: %s" % (sender,)
-        else:
-            requester = Requester(target_user, None, False)
-
-        message_handler = self.hs.get_handlers().message_handler
-        prev_event = message_handler.deduplicate_state_event(event, context)
-        if prev_event is not None:
-            return
-
-        action = "send"
-
-        if event.membership == Membership.JOIN:
-            if requester.is_guest and not self._can_guest_join(context.current_state):
-                # This should be an auth check, but guests are a local concept,
-                # so don't really fit into the general auth process.
-                raise AuthError(403, "Guest access not allowed")
-            do_remote_join_dance, remote_room_hosts = self._should_do_dance(
-                context,
-                (self.get_inviter(event.state_key, context.current_state)),
-                remote_room_hosts,
-            )
-            if do_remote_join_dance:
-                action = "remote_join"
-        elif event.membership == Membership.LEAVE:
-            is_host_in_room = self.is_host_in_room(context.current_state)
-
-            if not is_host_in_room:
-                # perhaps we've been invited
-                inviter = self.get_inviter(target_user.to_string(), context.current_state)
-                if not inviter:
-                    raise SynapseError(404, "Not a known room")
-
-                if self.hs.is_mine(inviter):
-                    # the inviter was on our server, but has now left. Carry on
-                    # with the normal rejection codepath.
-                    #
-                    # This is a bit of a hack, because the room might still be
-                    # active on other servers.
-                    pass
-                else:
-                    # send the rejection to the inviter's HS.
-                    remote_room_hosts = remote_room_hosts + [inviter.domain]
-                    action = "remote_reject"
-
-        federation_handler = self.hs.get_handlers().federation_handler
-
-        if action == "remote_join":
-            if len(remote_room_hosts) == 0:
-                raise SynapseError(404, "No known servers")
-
-            # We don't do an auth check if we are doing an invite
-            # join dance for now, since we're kinda implicitly checking
-            # that we are allowed to join when we decide whether or not we
-            # need to do the invite/join dance.
-            yield federation_handler.do_invite_join(
-                remote_room_hosts,
-                event.room_id,
-                event.user_id,
-                event.content,
-            )
-        elif action == "remote_reject":
-            yield federation_handler.do_remotely_reject_invite(
-                remote_room_hosts,
-                room_id,
-                event.user_id
-            )
-        else:
-            yield self.handle_new_client_event(
-                requester,
-                event,
-                context,
-                extra_users=[target_user],
-                ratelimit=ratelimit,
-            )
-
-        prev_member_event = context.current_state.get(
-            (EventTypes.Member, target_user.to_string()),
-            None
-        )
-
-        if event.membership == Membership.JOIN:
-            if not prev_member_event or prev_member_event.membership != Membership.JOIN:
-                # Only fire user_joined_room if the user has acutally joined the
-                # room. Don't bother if the user is just changing their profile
-                # info.
-                yield user_joined_room(self.distributor, target_user, room_id)
-        elif event.membership == Membership.LEAVE:
-            if prev_member_event and prev_member_event.membership == Membership.JOIN:
-                user_left_room(self.distributor, target_user, room_id)
-
-    def _can_guest_join(self, current_state):
-        """
-        Returns whether a guest can join a room based on its current state.
-        """
-        guest_access = current_state.get((EventTypes.GuestAccess, ""), None)
-        return (
-            guest_access
-            and guest_access.content
-            and "guest_access" in guest_access.content
-            and guest_access.content["guest_access"] == "can_join"
-        )
-
-    def _should_do_dance(self, context, inviter, room_hosts=None):
-        # TODO: Shouldn't this be remote_room_host?
-        room_hosts = room_hosts or []
-
-        is_host_in_room = self.is_host_in_room(context.current_state)
-        if is_host_in_room:
-            return False, room_hosts
-
-        if inviter and not self.hs.is_mine(inviter):
-            room_hosts.append(inviter.domain)
-
-        return True, room_hosts
-
-    @defer.inlineCallbacks
-    def lookup_room_alias(self, room_alias):
-        """
-        Get the room ID associated with a room alias.
-
-        Args:
-            room_alias (RoomAlias): The alias to look up.
-        Returns:
-            A tuple of:
-                The room ID as a RoomID object.
-                Hosts likely to be participating in the room ([str]).
-        Raises:
-            SynapseError if room alias could not be found.
-        """
-        directory_handler = self.hs.get_handlers().directory_handler
-        mapping = yield directory_handler.get_association(room_alias)
-
-        if not mapping:
-            raise SynapseError(404, "No such room alias")
-
-        room_id = mapping["room_id"]
-        servers = mapping["servers"]
-
-        defer.returnValue((RoomID.from_string(room_id), servers))
-
-    def get_inviter(self, user_id, current_state):
-        prev_state = current_state.get((EventTypes.Member, user_id))
-        if prev_state and prev_state.membership == Membership.INVITE:
-            return UserID.from_string(prev_state.user_id)
-        return None
-
-    @defer.inlineCallbacks
-    def get_joined_rooms_for_user(self, user):
-        """Returns a list of roomids that the user has any of the given
-        membership states in."""
-
-        rooms = yield self.store.get_rooms_for_user(
-            user.to_string(),
-        )
-
-        # For some reason the list of events contains duplicates
-        # TODO(paul): work out why because I really don't think it should
-        room_ids = set(r.room_id for r in rooms)
-
-        defer.returnValue(room_ids)
-
-    @defer.inlineCallbacks
-    def do_3pid_invite(
-            self,
-            room_id,
-            inviter,
-            medium,
-            address,
-            id_server,
-            requester,
-            txn_id
-    ):
-        invitee = yield self._lookup_3pid(
-            id_server, medium, address
-        )
-
-        if invitee:
-            handler = self.hs.get_handlers().room_member_handler
-            yield handler.update_membership(
-                requester,
-                UserID.from_string(invitee),
-                room_id,
-                "invite",
-                txn_id=txn_id,
-            )
-        else:
-            yield self._make_and_store_3pid_invite(
-                requester,
-                id_server,
-                medium,
-                address,
-                room_id,
-                inviter,
-                txn_id=txn_id
-            )
-
-    @defer.inlineCallbacks
-    def _lookup_3pid(self, id_server, medium, address):
-        """Looks up a 3pid in the passed identity server.
-
-        Args:
-            id_server (str): The server name (including port, if required)
-                of the identity server to use.
-            medium (str): The type of the third party identifier (e.g. "email").
-            address (str): The third party identifier (e.g. "foo@example.com").
-
-        Returns:
-            (str) the matrix ID of the 3pid, or None if it is not recognized.
-        """
-        try:
-            data = yield self.hs.get_simple_http_client().get_json(
-                "%s%s/_matrix/identity/api/v1/lookup" % (id_server_scheme, id_server,),
-                {
-                    "medium": medium,
-                    "address": address,
-                }
-            )
-
-            if "mxid" in data:
-                if "signatures" not in data:
-                    raise AuthError(401, "No signatures on 3pid binding")
-                self.verify_any_signature(data, id_server)
-                defer.returnValue(data["mxid"])
-
-        except IOError as e:
-            logger.warn("Error from identity server lookup: %s" % (e,))
-            defer.returnValue(None)
-
-    @defer.inlineCallbacks
-    def verify_any_signature(self, data, server_hostname):
-        if server_hostname not in data["signatures"]:
-            raise AuthError(401, "No signature from server %s" % (server_hostname,))
-        for key_name, signature in data["signatures"][server_hostname].items():
-            key_data = yield self.hs.get_simple_http_client().get_json(
-                "%s%s/_matrix/identity/api/v1/pubkey/%s" %
-                (id_server_scheme, server_hostname, key_name,),
-            )
-            if "public_key" not in key_data:
-                raise AuthError(401, "No public key named %s from %s" %
-                                (key_name, server_hostname,))
-            verify_signed_json(
-                data,
-                server_hostname,
-                decode_verify_key_bytes(key_name, decode_base64(key_data["public_key"]))
-            )
-            return
-
-    @defer.inlineCallbacks
-    def _make_and_store_3pid_invite(
-            self,
-            requester,
-            id_server,
-            medium,
-            address,
-            room_id,
-            user,
-            txn_id
-    ):
-        room_state = yield self.hs.get_state_handler().get_current_state(room_id)
-
-        inviter_display_name = ""
-        inviter_avatar_url = ""
-        member_event = room_state.get((EventTypes.Member, user.to_string()))
-        if member_event:
-            inviter_display_name = member_event.content.get("displayname", "")
-            inviter_avatar_url = member_event.content.get("avatar_url", "")
-
-        canonical_room_alias = ""
-        canonical_alias_event = room_state.get((EventTypes.CanonicalAlias, ""))
-        if canonical_alias_event:
-            canonical_room_alias = canonical_alias_event.content.get("alias", "")
-
-        room_name = ""
-        room_name_event = room_state.get((EventTypes.Name, ""))
-        if room_name_event:
-            room_name = room_name_event.content.get("name", "")
-
-        room_join_rules = ""
-        join_rules_event = room_state.get((EventTypes.JoinRules, ""))
-        if join_rules_event:
-            room_join_rules = join_rules_event.content.get("join_rule", "")
-
-        room_avatar_url = ""
-        room_avatar_event = room_state.get((EventTypes.RoomAvatar, ""))
-        if room_avatar_event:
-            room_avatar_url = room_avatar_event.content.get("url", "")
-
-        token, public_keys, fallback_public_key, display_name = (
-            yield self._ask_id_server_for_third_party_invite(
-                id_server=id_server,
-                medium=medium,
-                address=address,
-                room_id=room_id,
-                inviter_user_id=user.to_string(),
-                room_alias=canonical_room_alias,
-                room_avatar_url=room_avatar_url,
-                room_join_rules=room_join_rules,
-                room_name=room_name,
-                inviter_display_name=inviter_display_name,
-                inviter_avatar_url=inviter_avatar_url
-            )
-        )
-
-        msg_handler = self.hs.get_handlers().message_handler
-        yield msg_handler.create_and_send_nonmember_event(
-            requester,
-            {
-                "type": EventTypes.ThirdPartyInvite,
-                "content": {
-                    "display_name": display_name,
-                    "public_keys": public_keys,
-
-                    # For backwards compatibility:
-                    "key_validity_url": fallback_public_key["key_validity_url"],
-                    "public_key": fallback_public_key["public_key"],
-                },
-                "room_id": room_id,
-                "sender": user.to_string(),
-                "state_key": token,
-            },
-            txn_id=txn_id,
-        )
-
-    @defer.inlineCallbacks
-    def _ask_id_server_for_third_party_invite(
-            self,
-            id_server,
-            medium,
-            address,
-            room_id,
-            inviter_user_id,
-            room_alias,
-            room_avatar_url,
-            room_join_rules,
-            room_name,
-            inviter_display_name,
-            inviter_avatar_url
-    ):
-        """
-        Asks an identity server for a third party invite.
-
-        :param id_server (str): hostname + optional port for the identity server.
-        :param medium (str): The literal string "email".
-        :param address (str): The third party address being invited.
-        :param room_id (str): The ID of the room to which the user is invited.
-        :param inviter_user_id (str): The user ID of the inviter.
-        :param room_alias (str): An alias for the room, for cosmetic
-            notifications.
-        :param room_avatar_url (str): The URL of the room's avatar, for cosmetic
-            notifications.
-        :param room_join_rules (str): The join rules of the email
-            (e.g. "public").
-        :param room_name (str): The m.room.name of the room.
-        :param inviter_display_name (str): The current display name of the
-            inviter.
-        :param inviter_avatar_url (str): The URL of the inviter's avatar.
-
-        :return: A deferred tuple containing:
-            token (str): The token which must be signed to prove authenticity.
-            public_keys ([{"public_key": str, "key_validity_url": str}]):
-                public_key is a base64-encoded ed25519 public key.
-            fallback_public_key: One element from public_keys.
-            display_name (str): A user-friendly name to represent the invited
-                user.
-        """
-
-        is_url = "%s%s/_matrix/identity/api/v1/store-invite" % (
-            id_server_scheme, id_server,
-        )
-
-        invite_config = {
-            "medium": medium,
-            "address": address,
-            "room_id": room_id,
-            "room_alias": room_alias,
-            "room_avatar_url": room_avatar_url,
-            "room_join_rules": room_join_rules,
-            "room_name": room_name,
-            "sender": inviter_user_id,
-            "sender_display_name": inviter_display_name,
-            "sender_avatar_url": inviter_avatar_url,
-        }
-
-        if self.hs.config.invite_3pid_guest:
-            registration_handler = self.hs.get_handlers().registration_handler
-            guest_access_token = yield registration_handler.guest_access_token_for(
-                medium=medium,
-                address=address,
-                inviter_user_id=inviter_user_id,
-            )
-
-            guest_user_info = yield self.hs.get_auth().get_user_by_access_token(
-                guest_access_token
-            )
-
-            invite_config.update({
-                "guest_access_token": guest_access_token,
-                "guest_user_id": guest_user_info["user"].to_string(),
-            })
-
-        data = yield self.hs.get_simple_http_client().post_urlencoded_get_json(
-            is_url,
-            invite_config
-        )
-        # TODO: Check for success
-        token = data["token"]
-        public_keys = data.get("public_keys", [])
-        if "public_key" in data:
-            fallback_public_key = {
-                "public_key": data["public_key"],
-                "key_validity_url": "%s%s/_matrix/identity/api/v1/pubkey/isvalid" % (
-                    id_server_scheme, id_server,
-                ),
-            }
-        else:
-            fallback_public_key = public_keys[0]
-
-        if not public_keys:
-            public_keys.append(fallback_public_key)
-        display_name = data["display_name"]
-        defer.returnValue((token, public_keys, fallback_public_key, display_name))
-
-    @defer.inlineCallbacks
-    def forget(self, user, room_id):
-        user_id = user.to_string()
-
-        member = yield self.state_handler.get_current_state(
-            room_id=room_id,
-            event_type=EventTypes.Member,
-            state_key=user_id
-        )
-        membership = member.membership if member else None
-
-        if membership is not None and membership != Membership.LEAVE:
-            raise SynapseError(400, "User %s in room %s" % (
-                user_id, room_id
-            ))
-
-        if membership:
-            yield self.store.forget(user_id, room_id)
-
-
 class RoomListHandler(BaseHandler):
     def __init__(self, hs):
         super(RoomListHandler, self).__init__(hs)
@@ -965,6 +369,8 @@ class RoomListHandler(BaseHandler):
     def _get_public_room_list(self):
         room_ids = yield self.store.get_public_room_ids()
 
+        results = []
+
         @defer.inlineCallbacks
         def handle_room(room_id):
             aliases = yield self.store.get_aliases_for_room(room_id)
@@ -1025,18 +431,12 @@ class RoomListHandler(BaseHandler):
             joined_users = yield self.store.get_users_in_room(room_id)
             result["num_joined_members"] = len(joined_users)
 
-            defer.returnValue(result)
+            results.append(result)
 
-        result = []
-        for chunk in (room_ids[i:i + 10] for i in xrange(0, len(room_ids), 10)):
-            chunk_result = yield defer.gatherResults([
-                handle_room(room_id)
-                for room_id in chunk
-            ], consumeErrors=True).addErrback(unwrapFirstError)
-            result.extend(v for v in chunk_result if v)
+        yield concurrently_execute(handle_room, room_ids, 10)
 
         # FIXME (erikj): START is no longer a valid value
-        defer.returnValue({"start": "START", "end": "END", "chunk": result})
+        defer.returnValue({"start": "START", "end": "END", "chunk": results})
 
 
 class RoomContextHandler(BaseHandler):
diff --git a/synapse/handlers/room_member.py b/synapse/handlers/room_member.py
new file mode 100644
index 0000000000..8c41cb6f3c
--- /dev/null
+++ b/synapse/handlers/room_member.py
@@ -0,0 +1,718 @@
+# -*- coding: utf-8 -*-
+# 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.
+
+
+from twisted.internet import defer
+
+from ._base import BaseHandler
+
+from synapse.types import UserID, RoomID, Requester
+from synapse.api.constants import (
+    EventTypes, Membership,
+)
+from synapse.api.errors import AuthError, SynapseError, Codes
+from synapse.util.logcontext import preserve_context_over_fn
+
+from signedjson.sign import verify_signed_json
+from signedjson.key import decode_verify_key_bytes
+
+from unpaddedbase64 import decode_base64
+
+import logging
+
+logger = logging.getLogger(__name__)
+
+id_server_scheme = "https://"
+
+
+def user_left_room(distributor, user, room_id):
+    return preserve_context_over_fn(
+        distributor.fire,
+        "user_left_room", user=user, room_id=room_id
+    )
+
+
+def user_joined_room(distributor, user, room_id):
+    return preserve_context_over_fn(
+        distributor.fire,
+        "user_joined_room", user=user, room_id=room_id
+    )
+
+
+class RoomMemberHandler(BaseHandler):
+    # TODO(paul): This handler currently contains a messy conflation of
+    #   low-level API that works on UserID objects and so on, and REST-level
+    #   API that takes ID strings and returns pagination chunks. These concerns
+    #   ought to be separated out a lot better.
+
+    def __init__(self, hs):
+        super(RoomMemberHandler, self).__init__(hs)
+
+        self.clock = hs.get_clock()
+
+        self.distributor = hs.get_distributor()
+        self.distributor.declare("user_joined_room")
+        self.distributor.declare("user_left_room")
+
+    @defer.inlineCallbacks
+    def get_room_members(self, room_id):
+        users = yield self.store.get_users_in_room(room_id)
+
+        defer.returnValue([UserID.from_string(u) for u in users])
+
+    @defer.inlineCallbacks
+    def fetch_room_distributions_into(self, room_id, localusers=None,
+                                      remotedomains=None, ignore_user=None):
+        """Fetch the distribution of a room, adding elements to either
+        'localusers' or 'remotedomains', which should be a set() if supplied.
+        If ignore_user is set, ignore that user.
+
+        This function returns nothing; its result is performed by the
+        side-effect on the two passed sets. This allows easy accumulation of
+        member lists of multiple rooms at once if required.
+        """
+        members = yield self.get_room_members(room_id)
+        for member in members:
+            if ignore_user is not None and member == ignore_user:
+                continue
+
+            if self.hs.is_mine(member):
+                if localusers is not None:
+                    localusers.add(member)
+            else:
+                if remotedomains is not None:
+                    remotedomains.add(member.domain)
+
+    @defer.inlineCallbacks
+    def _local_membership_update(
+        self, requester, target, room_id, membership,
+        prev_event_ids,
+        txn_id=None,
+        ratelimit=True,
+    ):
+        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(
+            {
+                "type": EventTypes.Member,
+                "content": content,
+                "room_id": room_id,
+                "sender": requester.user.to_string(),
+                "state_key": target.to_string(),
+
+                # For backwards compatibility:
+                "membership": membership,
+            },
+            token_id=requester.access_token_id,
+            txn_id=txn_id,
+            prev_event_ids=prev_event_ids,
+        )
+
+        yield self.handle_new_client_event(
+            requester,
+            event,
+            context,
+            extra_users=[target],
+            ratelimit=ratelimit,
+        )
+
+        prev_member_event = context.current_state.get(
+            (EventTypes.Member, target.to_string()),
+            None
+        )
+
+        if event.membership == Membership.JOIN:
+            if not prev_member_event or prev_member_event.membership != Membership.JOIN:
+                # Only fire user_joined_room if the user has acutally joined the
+                # room. Don't bother if the user is just changing their profile
+                # info.
+                yield user_joined_room(self.distributor, target, room_id)
+        elif event.membership == Membership.LEAVE:
+            if prev_member_event and prev_member_event.membership == Membership.JOIN:
+                user_left_room(self.distributor, target, room_id)
+
+    @defer.inlineCallbacks
+    def remote_join(self, remote_room_hosts, room_id, user, content):
+        if len(remote_room_hosts) == 0:
+            raise SynapseError(404, "No known servers")
+
+        # We don't do an auth check if we are doing an invite
+        # join dance for now, since we're kinda implicitly checking
+        # that we are allowed to join when we decide whether or not we
+        # need to do the invite/join dance.
+        yield self.hs.get_handlers().federation_handler.do_invite_join(
+            remote_room_hosts,
+            room_id,
+            user.to_string(),
+            content,
+        )
+        yield user_joined_room(self.distributor, user, room_id)
+
+    def reject_remote_invite(self, user_id, room_id, remote_room_hosts):
+        return self.hs.get_handlers().federation_handler.do_remotely_reject_invite(
+            remote_room_hosts,
+            room_id,
+            user_id
+        )
+
+    @defer.inlineCallbacks
+    def update_membership(
+            self,
+            requester,
+            target,
+            room_id,
+            action,
+            txn_id=None,
+            remote_room_hosts=None,
+            third_party_signed=None,
+            ratelimit=True,
+    ):
+        effective_membership_state = action
+        if action in ["kick", "unban"]:
+            effective_membership_state = "leave"
+
+        if third_party_signed is not None:
+            replication = self.hs.get_replication_layer()
+            yield replication.exchange_third_party_invite(
+                third_party_signed["sender"],
+                target.to_string(),
+                room_id,
+                third_party_signed,
+            )
+
+        if not remote_room_hosts:
+            remote_room_hosts = []
+
+        latest_event_ids = yield self.store.get_latest_event_ids_in_room(room_id)
+        current_state = yield self.state_handler.get_current_state(
+            room_id, latest_event_ids=latest_event_ids,
+        )
+
+        old_state = current_state.get((EventTypes.Member, target.to_string()))
+        old_membership = old_state.content.get("membership") if old_state else None
+        if action == "unban" and old_membership != "ban":
+            raise SynapseError(
+                403,
+                "Cannot unban user who was not banned (membership=%s)" % old_membership,
+                errcode=Codes.BAD_STATE
+            )
+        if old_membership == "ban" and action != "unban":
+            raise SynapseError(
+                403,
+                "Cannot %s user who was is banned" % (action,),
+                errcode=Codes.BAD_STATE
+            )
+
+        is_host_in_room = self.is_host_in_room(current_state)
+
+        if effective_membership_state == Membership.JOIN:
+            if requester.is_guest and not self._can_guest_join(current_state):
+                # This should be an auth check, but guests are a local concept,
+                # so don't really fit into the general auth process.
+                raise AuthError(403, "Guest access not allowed")
+
+            if not is_host_in_room:
+                inviter = yield self.get_inviter(target.to_string(), room_id)
+                if inviter and not self.hs.is_mine(inviter):
+                    remote_room_hosts.append(inviter.domain)
+
+                content = {"membership": Membership.JOIN}
+
+                profile = self.hs.get_handlers().profile_handler
+                content["displayname"] = yield profile.get_displayname(target)
+                content["avatar_url"] = yield profile.get_avatar_url(target)
+
+                if requester.is_guest:
+                    content["kind"] = "guest"
+
+                ret = yield self.remote_join(
+                    remote_room_hosts, room_id, target, content
+                )
+                defer.returnValue(ret)
+
+        elif effective_membership_state == Membership.LEAVE:
+            if not is_host_in_room:
+                # perhaps we've been invited
+                inviter = yield self.get_inviter(target.to_string(), room_id)
+                if not inviter:
+                    raise SynapseError(404, "Not a known room")
+
+                if self.hs.is_mine(inviter):
+                    # the inviter was on our server, but has now left. Carry on
+                    # with the normal rejection codepath.
+                    #
+                    # This is a bit of a hack, because the room might still be
+                    # active on other servers.
+                    pass
+                else:
+                    # send the rejection to the inviter's HS.
+                    remote_room_hosts = remote_room_hosts + [inviter.domain]
+
+                    try:
+                        ret = yield self.reject_remote_invite(
+                            target.to_string(), room_id, remote_room_hosts
+                        )
+                        defer.returnValue(ret)
+                    except SynapseError as e:
+                        logger.warn("Failed to reject invite: %s", e)
+
+                        yield self.store.locally_reject_invite(
+                            target.to_string(), room_id
+                        )
+
+                        defer.returnValue({})
+
+        yield self._local_membership_update(
+            requester=requester,
+            target=target,
+            room_id=room_id,
+            membership=effective_membership_state,
+            txn_id=txn_id,
+            ratelimit=ratelimit,
+            prev_event_ids=latest_event_ids,
+        )
+
+    @defer.inlineCallbacks
+    def send_membership_event(
+            self,
+            requester,
+            event,
+            context,
+            remote_room_hosts=None,
+            ratelimit=True,
+    ):
+        """
+        Change the membership status of a user in a room.
+
+        Args:
+            requester (Requester): The local user who requested the membership
+                event. If None, certain checks, like whether this homeserver can
+                act as the sender, will be skipped.
+            event (SynapseEvent): The membership event.
+            context: The context of the event.
+            is_guest (bool): Whether the sender is a guest.
+            room_hosts ([str]): Homeservers which are likely to already be in
+                the room, and could be danced with in order to join this
+                homeserver for the first time.
+            ratelimit (bool): Whether to rate limit this request.
+        Raises:
+            SynapseError if there was a problem changing the membership.
+        """
+        remote_room_hosts = remote_room_hosts or []
+
+        target_user = UserID.from_string(event.state_key)
+        room_id = event.room_id
+
+        if requester is not None:
+            sender = UserID.from_string(event.sender)
+            assert sender == requester.user, (
+                "Sender (%s) must be same as requester (%s)" %
+                (sender, requester.user)
+            )
+            assert self.hs.is_mine(sender), "Sender must be our own: %s" % (sender,)
+        else:
+            requester = Requester(target_user, None, False)
+
+        message_handler = self.hs.get_handlers().message_handler
+        prev_event = message_handler.deduplicate_state_event(event, context)
+        if prev_event is not None:
+            return
+
+        if event.membership == Membership.JOIN:
+            if requester.is_guest and not self._can_guest_join(context.current_state):
+                # This should be an auth check, but guests are a local concept,
+                # so don't really fit into the general auth process.
+                raise AuthError(403, "Guest access not allowed")
+
+        yield self.handle_new_client_event(
+            requester,
+            event,
+            context,
+            extra_users=[target_user],
+            ratelimit=ratelimit,
+        )
+
+        prev_member_event = context.current_state.get(
+            (EventTypes.Member, target_user.to_string()),
+            None
+        )
+
+        if event.membership == Membership.JOIN:
+            if not prev_member_event or prev_member_event.membership != Membership.JOIN:
+                # Only fire user_joined_room if the user has acutally joined the
+                # room. Don't bother if the user is just changing their profile
+                # info.
+                yield user_joined_room(self.distributor, target_user, room_id)
+        elif event.membership == Membership.LEAVE:
+            if prev_member_event and prev_member_event.membership == Membership.JOIN:
+                user_left_room(self.distributor, target_user, room_id)
+
+    def _can_guest_join(self, current_state):
+        """
+        Returns whether a guest can join a room based on its current state.
+        """
+        guest_access = current_state.get((EventTypes.GuestAccess, ""), None)
+        return (
+            guest_access
+            and guest_access.content
+            and "guest_access" in guest_access.content
+            and guest_access.content["guest_access"] == "can_join"
+        )
+
+    def _should_do_dance(self, current_state, inviter, room_hosts=None):
+        # TODO: Shouldn't this be remote_room_host?
+        room_hosts = room_hosts or []
+
+        is_host_in_room = self.is_host_in_room(current_state)
+        if is_host_in_room:
+            return False, room_hosts
+
+        if inviter and not self.hs.is_mine(inviter):
+            room_hosts.append(inviter.domain)
+
+        return True, room_hosts
+
+    @defer.inlineCallbacks
+    def lookup_room_alias(self, room_alias):
+        """
+        Get the room ID associated with a room alias.
+
+        Args:
+            room_alias (RoomAlias): The alias to look up.
+        Returns:
+            A tuple of:
+                The room ID as a RoomID object.
+                Hosts likely to be participating in the room ([str]).
+        Raises:
+            SynapseError if room alias could not be found.
+        """
+        directory_handler = self.hs.get_handlers().directory_handler
+        mapping = yield directory_handler.get_association(room_alias)
+
+        if not mapping:
+            raise SynapseError(404, "No such room alias")
+
+        room_id = mapping["room_id"]
+        servers = mapping["servers"]
+
+        defer.returnValue((RoomID.from_string(room_id), servers))
+
+    @defer.inlineCallbacks
+    def get_inviter(self, user_id, room_id):
+        invite = yield self.store.get_invite_for_user_in_room(
+            user_id=user_id,
+            room_id=room_id,
+        )
+        if invite:
+            defer.returnValue(UserID.from_string(invite.sender))
+
+    @defer.inlineCallbacks
+    def get_joined_rooms_for_user(self, user):
+        """Returns a list of roomids that the user has any of the given
+        membership states in."""
+
+        rooms = yield self.store.get_rooms_for_user(
+            user.to_string(),
+        )
+
+        # For some reason the list of events contains duplicates
+        # TODO(paul): work out why because I really don't think it should
+        room_ids = set(r.room_id for r in rooms)
+
+        defer.returnValue(room_ids)
+
+    @defer.inlineCallbacks
+    def do_3pid_invite(
+            self,
+            room_id,
+            inviter,
+            medium,
+            address,
+            id_server,
+            requester,
+            txn_id
+    ):
+        invitee = yield self._lookup_3pid(
+            id_server, medium, address
+        )
+
+        if invitee:
+            handler = self.hs.get_handlers().room_member_handler
+            yield handler.update_membership(
+                requester,
+                UserID.from_string(invitee),
+                room_id,
+                "invite",
+                txn_id=txn_id,
+            )
+        else:
+            yield self._make_and_store_3pid_invite(
+                requester,
+                id_server,
+                medium,
+                address,
+                room_id,
+                inviter,
+                txn_id=txn_id
+            )
+
+    @defer.inlineCallbacks
+    def _lookup_3pid(self, id_server, medium, address):
+        """Looks up a 3pid in the passed identity server.
+
+        Args:
+            id_server (str): The server name (including port, if required)
+                of the identity server to use.
+            medium (str): The type of the third party identifier (e.g. "email").
+            address (str): The third party identifier (e.g. "foo@example.com").
+
+        Returns:
+            str: the matrix ID of the 3pid, or None if it is not recognized.
+        """
+        try:
+            data = yield self.hs.get_simple_http_client().get_json(
+                "%s%s/_matrix/identity/api/v1/lookup" % (id_server_scheme, id_server,),
+                {
+                    "medium": medium,
+                    "address": address,
+                }
+            )
+
+            if "mxid" in data:
+                if "signatures" not in data:
+                    raise AuthError(401, "No signatures on 3pid binding")
+                self.verify_any_signature(data, id_server)
+                defer.returnValue(data["mxid"])
+
+        except IOError as e:
+            logger.warn("Error from identity server lookup: %s" % (e,))
+            defer.returnValue(None)
+
+    @defer.inlineCallbacks
+    def verify_any_signature(self, data, server_hostname):
+        if server_hostname not in data["signatures"]:
+            raise AuthError(401, "No signature from server %s" % (server_hostname,))
+        for key_name, signature in data["signatures"][server_hostname].items():
+            key_data = yield self.hs.get_simple_http_client().get_json(
+                "%s%s/_matrix/identity/api/v1/pubkey/%s" %
+                (id_server_scheme, server_hostname, key_name,),
+            )
+            if "public_key" not in key_data:
+                raise AuthError(401, "No public key named %s from %s" %
+                                (key_name, server_hostname,))
+            verify_signed_json(
+                data,
+                server_hostname,
+                decode_verify_key_bytes(key_name, decode_base64(key_data["public_key"]))
+            )
+            return
+
+    @defer.inlineCallbacks
+    def _make_and_store_3pid_invite(
+            self,
+            requester,
+            id_server,
+            medium,
+            address,
+            room_id,
+            user,
+            txn_id
+    ):
+        room_state = yield self.hs.get_state_handler().get_current_state(room_id)
+
+        inviter_display_name = ""
+        inviter_avatar_url = ""
+        member_event = room_state.get((EventTypes.Member, user.to_string()))
+        if member_event:
+            inviter_display_name = member_event.content.get("displayname", "")
+            inviter_avatar_url = member_event.content.get("avatar_url", "")
+
+        canonical_room_alias = ""
+        canonical_alias_event = room_state.get((EventTypes.CanonicalAlias, ""))
+        if canonical_alias_event:
+            canonical_room_alias = canonical_alias_event.content.get("alias", "")
+
+        room_name = ""
+        room_name_event = room_state.get((EventTypes.Name, ""))
+        if room_name_event:
+            room_name = room_name_event.content.get("name", "")
+
+        room_join_rules = ""
+        join_rules_event = room_state.get((EventTypes.JoinRules, ""))
+        if join_rules_event:
+            room_join_rules = join_rules_event.content.get("join_rule", "")
+
+        room_avatar_url = ""
+        room_avatar_event = room_state.get((EventTypes.RoomAvatar, ""))
+        if room_avatar_event:
+            room_avatar_url = room_avatar_event.content.get("url", "")
+
+        token, public_keys, fallback_public_key, display_name = (
+            yield self._ask_id_server_for_third_party_invite(
+                id_server=id_server,
+                medium=medium,
+                address=address,
+                room_id=room_id,
+                inviter_user_id=user.to_string(),
+                room_alias=canonical_room_alias,
+                room_avatar_url=room_avatar_url,
+                room_join_rules=room_join_rules,
+                room_name=room_name,
+                inviter_display_name=inviter_display_name,
+                inviter_avatar_url=inviter_avatar_url
+            )
+        )
+
+        msg_handler = self.hs.get_handlers().message_handler
+        yield msg_handler.create_and_send_nonmember_event(
+            requester,
+            {
+                "type": EventTypes.ThirdPartyInvite,
+                "content": {
+                    "display_name": display_name,
+                    "public_keys": public_keys,
+
+                    # For backwards compatibility:
+                    "key_validity_url": fallback_public_key["key_validity_url"],
+                    "public_key": fallback_public_key["public_key"],
+                },
+                "room_id": room_id,
+                "sender": user.to_string(),
+                "state_key": token,
+            },
+            txn_id=txn_id,
+        )
+
+    @defer.inlineCallbacks
+    def _ask_id_server_for_third_party_invite(
+            self,
+            id_server,
+            medium,
+            address,
+            room_id,
+            inviter_user_id,
+            room_alias,
+            room_avatar_url,
+            room_join_rules,
+            room_name,
+            inviter_display_name,
+            inviter_avatar_url
+    ):
+        """
+        Asks an identity server for a third party invite.
+
+        Args:
+            id_server (str): hostname + optional port for the identity server.
+            medium (str): The literal string "email".
+            address (str): The third party address being invited.
+            room_id (str): The ID of the room to which the user is invited.
+            inviter_user_id (str): The user ID of the inviter.
+            room_alias (str): An alias for the room, for cosmetic notifications.
+            room_avatar_url (str): The URL of the room's avatar, for cosmetic
+                notifications.
+            room_join_rules (str): The join rules of the email (e.g. "public").
+            room_name (str): The m.room.name of the room.
+            inviter_display_name (str): The current display name of the
+                inviter.
+            inviter_avatar_url (str): The URL of the inviter's avatar.
+
+        Returns:
+            A deferred tuple containing:
+                token (str): The token which must be signed to prove authenticity.
+                public_keys ([{"public_key": str, "key_validity_url": str}]):
+                    public_key is a base64-encoded ed25519 public key.
+                fallback_public_key: One element from public_keys.
+                display_name (str): A user-friendly name to represent the invited
+                    user.
+        """
+
+        is_url = "%s%s/_matrix/identity/api/v1/store-invite" % (
+            id_server_scheme, id_server,
+        )
+
+        invite_config = {
+            "medium": medium,
+            "address": address,
+            "room_id": room_id,
+            "room_alias": room_alias,
+            "room_avatar_url": room_avatar_url,
+            "room_join_rules": room_join_rules,
+            "room_name": room_name,
+            "sender": inviter_user_id,
+            "sender_display_name": inviter_display_name,
+            "sender_avatar_url": inviter_avatar_url,
+        }
+
+        if self.hs.config.invite_3pid_guest:
+            registration_handler = self.hs.get_handlers().registration_handler
+            guest_access_token = yield registration_handler.guest_access_token_for(
+                medium=medium,
+                address=address,
+                inviter_user_id=inviter_user_id,
+            )
+
+            guest_user_info = yield self.hs.get_auth().get_user_by_access_token(
+                guest_access_token
+            )
+
+            invite_config.update({
+                "guest_access_token": guest_access_token,
+                "guest_user_id": guest_user_info["user"].to_string(),
+            })
+
+        data = yield self.hs.get_simple_http_client().post_urlencoded_get_json(
+            is_url,
+            invite_config
+        )
+        # TODO: Check for success
+        token = data["token"]
+        public_keys = data.get("public_keys", [])
+        if "public_key" in data:
+            fallback_public_key = {
+                "public_key": data["public_key"],
+                "key_validity_url": "%s%s/_matrix/identity/api/v1/pubkey/isvalid" % (
+                    id_server_scheme, id_server,
+                ),
+            }
+        else:
+            fallback_public_key = public_keys[0]
+
+        if not public_keys:
+            public_keys.append(fallback_public_key)
+        display_name = data["display_name"]
+        defer.returnValue((token, public_keys, fallback_public_key, display_name))
+
+    @defer.inlineCallbacks
+    def forget(self, user, room_id):
+        user_id = user.to_string()
+
+        member = yield self.state_handler.get_current_state(
+            room_id=room_id,
+            event_type=EventTypes.Member,
+            state_key=user_id
+        )
+        membership = member.membership if member else None
+
+        if membership is not None and membership != Membership.LEAVE:
+            raise SynapseError(400, "User %s in room %s" % (
+                user_id, room_id
+            ))
+
+        if membership:
+            yield self.store.forget(user_id, room_id)
diff --git a/synapse/handlers/sync.py b/synapse/handlers/sync.py
index 48ab5707e1..231140b655 100644
--- a/synapse/handlers/sync.py
+++ b/synapse/handlers/sync.py
@@ -17,8 +17,8 @@ from ._base import BaseHandler
 
 from synapse.streams.config import PaginationConfig
 from synapse.api.constants import Membership, EventTypes
-from synapse.util import unwrapFirstError
-from synapse.util.logcontext import LoggingContext, preserve_fn
+from synapse.util.async import concurrently_execute
+from synapse.util.logcontext import LoggingContext
 from synapse.util.metrics import Measure
 from synapse.util.caches.response_cache import ResponseCache
 from synapse.push.clientformat import format_push_rules_for_user
@@ -250,58 +250,50 @@ class SyncHandler(BaseHandler):
         joined = []
         invited = []
         archived = []
-        deferreds = []
-
-        room_list_chunks = [room_list[i:i + 10] for i in xrange(0, len(room_list), 10)]
-        for room_list_chunk in room_list_chunks:
-            for event in room_list_chunk:
-                if event.membership == Membership.JOIN:
-                    room_sync_deferred = preserve_fn(
-                        self.full_state_sync_for_joined_room
-                    )(
-                        room_id=event.room_id,
-                        sync_config=sync_config,
-                        now_token=now_token,
-                        timeline_since_token=timeline_since_token,
-                        ephemeral_by_room=ephemeral_by_room,
-                        tags_by_room=tags_by_room,
-                        account_data_by_room=account_data_by_room,
-                    )
-                    room_sync_deferred.addCallback(joined.append)
-                    deferreds.append(room_sync_deferred)
-                elif event.membership == Membership.INVITE:
-                    invite = yield self.store.get_event(event.event_id)
-                    invited.append(InvitedSyncResult(
-                        room_id=event.room_id,
-                        invite=invite,
-                    ))
-                elif event.membership in (Membership.LEAVE, Membership.BAN):
-                    # Always send down rooms we were banned or kicked from.
-                    if not sync_config.filter_collection.include_leave:
-                        if event.membership == Membership.LEAVE:
-                            if sync_config.user.to_string() == event.sender:
-                                continue
-
-                    leave_token = now_token.copy_and_replace(
-                        "room_key", "s%d" % (event.stream_ordering,)
-                    )
-                    room_sync_deferred = preserve_fn(
-                        self.full_state_sync_for_archived_room
-                    )(
-                        sync_config=sync_config,
-                        room_id=event.room_id,
-                        leave_event_id=event.event_id,
-                        leave_token=leave_token,
-                        timeline_since_token=timeline_since_token,
-                        tags_by_room=tags_by_room,
-                        account_data_by_room=account_data_by_room,
-                    )
-                    room_sync_deferred.addCallback(archived.append)
-                    deferreds.append(room_sync_deferred)
 
-            yield defer.gatherResults(
-                deferreds, consumeErrors=True
-            ).addErrback(unwrapFirstError)
+        user_id = sync_config.user.to_string()
+
+        @defer.inlineCallbacks
+        def _generate_room_entry(event):
+            if event.membership == Membership.JOIN:
+                room_result = yield self.full_state_sync_for_joined_room(
+                    room_id=event.room_id,
+                    sync_config=sync_config,
+                    now_token=now_token,
+                    timeline_since_token=timeline_since_token,
+                    ephemeral_by_room=ephemeral_by_room,
+                    tags_by_room=tags_by_room,
+                    account_data_by_room=account_data_by_room,
+                )
+                joined.append(room_result)
+            elif event.membership == Membership.INVITE:
+                invite = yield self.store.get_event(event.event_id)
+                invited.append(InvitedSyncResult(
+                    room_id=event.room_id,
+                    invite=invite,
+                ))
+            elif event.membership in (Membership.LEAVE, Membership.BAN):
+                # Always send down rooms we were banned or kicked from.
+                if not sync_config.filter_collection.include_leave:
+                    if event.membership == Membership.LEAVE:
+                        if user_id == event.sender:
+                            return
+
+                leave_token = now_token.copy_and_replace(
+                    "room_key", "s%d" % (event.stream_ordering,)
+                )
+                room_result = yield self.full_state_sync_for_archived_room(
+                    sync_config=sync_config,
+                    room_id=event.room_id,
+                    leave_event_id=event.event_id,
+                    leave_token=leave_token,
+                    timeline_since_token=timeline_since_token,
+                    tags_by_room=tags_by_room,
+                    account_data_by_room=account_data_by_room,
+                )
+                archived.append(room_result)
+
+        yield concurrently_execute(_generate_room_entry, room_list, 10)
 
         account_data_for_user = sync_config.filter_collection.filter_account_data(
             self.account_data_for_user(account_data)
@@ -671,7 +663,8 @@ class SyncHandler(BaseHandler):
     def load_filtered_recents(self, room_id, sync_config, now_token,
                               since_token=None, recents=None, newly_joined_room=False):
         """
-        :returns a Deferred TimelineBatch
+        Returns:
+            a Deferred TimelineBatch
         """
         with Measure(self.clock, "load_filtered_recents"):
             filtering_factor = 2
@@ -838,8 +831,11 @@ class SyncHandler(BaseHandler):
         """
         Get the room state after the given event
 
-        :param synapse.events.EventBase event: event of interest
-        :return: A Deferred map from ((type, state_key)->Event)
+        Args:
+            event(synapse.events.EventBase): event of interest
+
+        Returns:
+            A Deferred map from ((type, state_key)->Event)
         """
         state = yield self.store.get_state_for_event(event.event_id)
         if event.is_state():
@@ -850,9 +846,13 @@ class SyncHandler(BaseHandler):
     @defer.inlineCallbacks
     def get_state_at(self, room_id, stream_position):
         """ Get the room state at a particular stream position
-        :param str room_id: room for which to get state
-        :param StreamToken stream_position: point at which to get state
-        :returns: A Deferred map from ((type, state_key)->Event)
+
+        Args:
+            room_id(str): room for which to get state
+            stream_position(StreamToken): point at which to get state
+
+        Returns:
+            A Deferred map from ((type, state_key)->Event)
         """
         last_events, token = yield self.store.get_recent_events_for_room(
             room_id, end_token=stream_position.room_key, limit=1,
@@ -873,15 +873,18 @@ class SyncHandler(BaseHandler):
         """ Works out the differnce in state between the start of the timeline
         and the previous sync.
 
-        :param str room_id
-        :param TimelineBatch batch: The timeline batch for the room that will
-            be sent to the user.
-        :param sync_config
-        :param str since_token: Token of the end of the previous batch. May be None.
-        :param str now_token: Token of the end of the current batch.
-        :param bool full_state: Whether to force returning the full state.
+        Args:
+            room_id(str):
+            batch(synapse.handlers.sync.TimelineBatch): The timeline batch for
+                the room that will be sent to the user.
+            sync_config(synapse.handlers.sync.SyncConfig):
+            since_token(str|None): Token of the end of the previous batch. May
+                be None.
+            now_token(str): Token of the end of the current batch.
+            full_state(bool): Whether to force returning the full state.
 
-        :returns A new event dictionary
+        Returns:
+             A deferred new event dictionary
         """
         # TODO(mjark) Check if the state events were received by the server
         # after the previous sync, since we need to include those state
@@ -953,11 +956,13 @@ class SyncHandler(BaseHandler):
         Check if the user has just joined the given room (so should
         be given the full state)
 
-        :param sync_config:
-        :param dict[(str,str), synapse.events.FrozenEvent] state_delta: the
-           difference in state since the last sync
+        Args:
+            sync_config(synapse.handlers.sync.SyncConfig):
+            state_delta(dict[(str,str), synapse.events.FrozenEvent]): the
+                difference in state since the last sync
 
-        :returns A deferred Tuple (state_delta, limited)
+        Returns:
+             A deferred Tuple (state_delta, limited)
         """
         join_event = state_delta.get((
             EventTypes.Member, sync_config.user.to_string()), None)