diff --git a/synapse/handlers/pagination.py b/synapse/handlers/pagination.py
new file mode 100644
index 0000000000..b2849783ed
--- /dev/null
+++ b/synapse/handlers/pagination.py
@@ -0,0 +1,265 @@
+# -*- coding: utf-8 -*-
+# Copyright 2014 - 2016 OpenMarket 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.
+# 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.
+import logging
+
+from twisted.internet import defer
+from twisted.python.failure import Failure
+
+from synapse.api.constants import Membership
+from synapse.api.errors import SynapseError
+from synapse.events.utils import serialize_event
+from synapse.types import RoomStreamToken
+from synapse.util.async import ReadWriteLock
+from synapse.util.logcontext import run_in_background
+from synapse.util.stringutils import random_string
+from synapse.visibility import filter_events_for_client
+
+logger = logging.getLogger(__name__)
+
+
+class PurgeStatus(object):
+ """Object tracking the status of a purge request
+
+ This class contains information on the progress of a purge request, for
+ return by get_purge_status.
+
+ Attributes:
+ status (int): Tracks whether this request has completed. One of
+ STATUS_{ACTIVE,COMPLETE,FAILED}
+ """
+
+ STATUS_ACTIVE = 0
+ STATUS_COMPLETE = 1
+ STATUS_FAILED = 2
+
+ STATUS_TEXT = {
+ STATUS_ACTIVE: "active",
+ STATUS_COMPLETE: "complete",
+ STATUS_FAILED: "failed",
+ }
+
+ def __init__(self):
+ self.status = PurgeStatus.STATUS_ACTIVE
+
+ def asdict(self):
+ return {
+ "status": PurgeStatus.STATUS_TEXT[self.status]
+ }
+
+
+class PaginationHandler(object):
+ """Handles pagination and purge history requests.
+
+ These are in the same handler due to the fact we need to block clients
+ paginating during a purge.
+ """
+
+ def __init__(self, hs):
+ self.hs = hs
+ self.auth = hs.get_auth()
+ self.store = hs.get_datastore()
+ self.clock = hs.get_clock()
+
+ self.pagination_lock = ReadWriteLock()
+ self._purges_in_progress_by_room = set()
+ # map from purge id to PurgeStatus
+ self._purges_by_id = {}
+
+ def start_purge_history(self, room_id, token,
+ delete_local_events=False):
+ """Start off a history purge on a room.
+
+ Args:
+ room_id (str): The room to purge from
+
+ token (str): topological token to delete events before
+ delete_local_events (bool): True to delete local events as well as
+ remote ones
+
+ Returns:
+ str: unique ID for this purge transaction.
+ """
+ if room_id in self._purges_in_progress_by_room:
+ raise SynapseError(
+ 400,
+ "History purge already in progress for %s" % (room_id, ),
+ )
+
+ purge_id = random_string(16)
+
+ # we log the purge_id here so that it can be tied back to the
+ # request id in the log lines.
+ logger.info("[purge] starting purge_id %s", purge_id)
+
+ self._purges_by_id[purge_id] = PurgeStatus()
+ run_in_background(
+ self._purge_history,
+ purge_id, room_id, token, delete_local_events,
+ )
+ return purge_id
+
+ @defer.inlineCallbacks
+ def _purge_history(self, purge_id, room_id, token,
+ delete_local_events):
+ """Carry out a history purge on a room.
+
+ Args:
+ purge_id (str): The id for this purge
+ room_id (str): The room to purge from
+ token (str): topological token to delete events before
+ delete_local_events (bool): True to delete local events as well as
+ remote ones
+
+ Returns:
+ Deferred
+ """
+ self._purges_in_progress_by_room.add(room_id)
+ try:
+ with (yield self.pagination_lock.write(room_id)):
+ yield self.store.purge_history(
+ room_id, token, delete_local_events,
+ )
+ logger.info("[purge] complete")
+ self._purges_by_id[purge_id].status = PurgeStatus.STATUS_COMPLETE
+ except Exception:
+ logger.error("[purge] failed: %s", Failure().getTraceback().rstrip())
+ self._purges_by_id[purge_id].status = PurgeStatus.STATUS_FAILED
+ finally:
+ self._purges_in_progress_by_room.discard(room_id)
+
+ # remove the purge from the list 24 hours after it completes
+ def clear_purge():
+ del self._purges_by_id[purge_id]
+ self.hs.get_reactor().callLater(24 * 3600, clear_purge)
+
+ def get_purge_status(self, purge_id):
+ """Get the current status of an active purge
+
+ Args:
+ purge_id (str): purge_id returned by start_purge_history
+
+ Returns:
+ PurgeStatus|None
+ """
+ return self._purges_by_id.get(purge_id)
+
+ @defer.inlineCallbacks
+ def get_messages(self, requester, room_id=None, pagin_config=None,
+ as_client_event=True, event_filter=None):
+ """Get messages in a room.
+
+ Args:
+ requester (Requester): The user requesting messages.
+ room_id (str): The room they want messages from.
+ pagin_config (synapse.api.streams.PaginationConfig): The pagination
+ config rules to apply, if any.
+ as_client_event (bool): True to get events in client-server format.
+ event_filter (Filter): Filter to apply to results or None
+ Returns:
+ dict: Pagination API results
+ """
+ user_id = requester.user.to_string()
+
+ if pagin_config.from_token:
+ room_token = pagin_config.from_token.room_key
+ else:
+ pagin_config.from_token = (
+ yield self.hs.get_event_sources().get_current_token_for_room(
+ room_id=room_id
+ )
+ )
+ room_token = pagin_config.from_token.room_key
+
+ room_token = RoomStreamToken.parse(room_token)
+
+ pagin_config.from_token = pagin_config.from_token.copy_and_replace(
+ "room_key", str(room_token)
+ )
+
+ source_config = pagin_config.get_source_config("room")
+
+ with (yield self.pagination_lock.read(room_id)):
+ membership, member_event_id = yield self.auth.check_in_room_or_world_readable(
+ room_id, user_id
+ )
+
+ if source_config.direction == 'b':
+ # if we're going backwards, we might need to backfill. This
+ # requires that we have a topo token.
+ if room_token.topological:
+ max_topo = room_token.topological
+ else:
+ max_topo = yield self.store.get_max_topological_token(
+ room_id, room_token.stream
+ )
+
+ if membership == Membership.LEAVE:
+ # If they have left the room then clamp the token to be before
+ # they left the room, to save the effort of loading from the
+ # database.
+ leave_token = yield self.store.get_topological_token_for_event(
+ member_event_id
+ )
+ leave_token = RoomStreamToken.parse(leave_token)
+ if leave_token.topological < max_topo:
+ source_config.from_key = str(leave_token)
+
+ yield self.hs.get_handlers().federation_handler.maybe_backfill(
+ room_id, max_topo
+ )
+
+ events, next_key = yield self.store.paginate_room_events(
+ room_id=room_id,
+ from_key=source_config.from_key,
+ to_key=source_config.to_key,
+ direction=source_config.direction,
+ limit=source_config.limit,
+ event_filter=event_filter,
+ )
+
+ next_token = pagin_config.from_token.copy_and_replace(
+ "room_key", next_key
+ )
+
+ if not events:
+ defer.returnValue({
+ "chunk": [],
+ "start": pagin_config.from_token.to_string(),
+ "end": next_token.to_string(),
+ })
+
+ if event_filter:
+ events = event_filter.filter(events)
+
+ events = yield filter_events_for_client(
+ self.store,
+ user_id,
+ events,
+ is_peeking=(member_event_id is None),
+ )
+
+ time_now = self.clock.time_msec()
+
+ chunk = {
+ "chunk": [
+ serialize_event(e, time_now, as_client_event)
+ for e in events
+ ],
+ "start": pagin_config.from_token.to_string(),
+ "end": next_token.to_string(),
+ }
+
+ defer.returnValue(chunk)
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