synapse-product/synapse/replication/http/streams.py
Erik Johnston 1531b214fc
Add ability to wait for replication streams (#7542)
The idea here is that if an instance persists an event via the replication HTTP API it can return before we receive that event over replication, which can lead to races where code assumes that persisting an event immediately updates various caches (e.g. current state of the room).

Most of Synapse doesn't hit such races, so we don't do the waiting automagically, instead we do so where necessary to avoid unnecessary delays. We may decide to change our minds here if it turns out there are a lot of subtle races going on.

People probably want to look at this commit by commit.
2020-05-22 14:21:54 +01:00

80 lines
2.5 KiB
Python

# -*- coding: utf-8 -*-
# Copyright 2020 The Matrix.org Foundation C.I.C.
#
# 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 synapse.api.errors import SynapseError
from synapse.http.servlet import parse_integer
from synapse.replication.http._base import ReplicationEndpoint
logger = logging.getLogger(__name__)
class ReplicationGetStreamUpdates(ReplicationEndpoint):
"""Fetches stream updates from a server. Used for streams not persisted to
the database, e.g. typing notifications.
The API looks like:
GET /_synapse/replication/get_repl_stream_updates/<stream name>?from_token=0&to_token=10
200 OK
{
updates: [ ... ],
upto_token: 10,
limited: False,
}
If there are more rows than can sensibly be returned in one lump, `limited` will be
set to true, and the caller should call again with a new `from_token`.
"""
NAME = "get_repl_stream_updates"
PATH_ARGS = ("stream_name",)
METHOD = "GET"
def __init__(self, hs):
super().__init__(hs)
self._instance_name = hs.get_instance_name()
self.streams = hs.get_replication_streams()
@staticmethod
def _serialize_payload(stream_name, from_token, upto_token):
return {"from_token": from_token, "upto_token": upto_token}
async def _handle_request(self, request, stream_name):
stream = self.streams.get(stream_name)
if stream is None:
raise SynapseError(400, "Unknown stream")
from_token = parse_integer(request, "from_token", required=True)
upto_token = parse_integer(request, "upto_token", required=True)
updates, upto_token, limited = await stream.get_updates_since(
self._instance_name, from_token, upto_token
)
return (
200,
{"updates": updates, "upto_token": upto_token, "limited": limited},
)
def register_servlets(hs, http_server):
ReplicationGetStreamUpdates(hs).register(http_server)