anonymousland-synapse/synapse/federation/sender/__init__.py
Richard van der Hoff a902d13180
Batch up outgoing read-receipts to reduce federation traffic. (#4890)
Rate-limit outgoing read-receipts as per #4730.
2019-03-20 16:02:25 +00:00

466 lines
18 KiB
Python

# -*- coding: utf-8 -*-
# Copyright 2019 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 six import itervalues
from prometheus_client import Counter
from twisted.internet import defer
import synapse.metrics
from synapse.federation.sender.per_destination_queue import PerDestinationQueue
from synapse.federation.sender.transaction_manager import TransactionManager
from synapse.federation.units import Edu
from synapse.handlers.presence import get_interested_remotes
from synapse.metrics import (
LaterGauge,
event_processing_loop_counter,
event_processing_loop_room_count,
events_processed_counter,
)
from synapse.metrics.background_process_metrics import run_as_background_process
from synapse.util import logcontext
from synapse.util.metrics import measure_func
logger = logging.getLogger(__name__)
sent_pdus_destination_dist_count = Counter(
"synapse_federation_client_sent_pdu_destinations:count",
"Number of PDUs queued for sending to one or more destinations",
)
sent_pdus_destination_dist_total = Counter(
"synapse_federation_client_sent_pdu_destinations:total", ""
"Total number of PDUs queued for sending across all destinations",
)
class FederationSender(object):
def __init__(self, hs):
self.hs = hs
self.server_name = hs.hostname
self.store = hs.get_datastore()
self.state = hs.get_state_handler()
self.clock = hs.get_clock()
self.is_mine_id = hs.is_mine_id
self._transaction_manager = TransactionManager(hs)
# map from destination to PerDestinationQueue
self._per_destination_queues = {} # type: dict[str, PerDestinationQueue]
LaterGauge(
"synapse_federation_transaction_queue_pending_destinations",
"",
[],
lambda: sum(
1 for d in self._per_destination_queues.values()
if d.transmission_loop_running
),
)
# Map of user_id -> UserPresenceState for all the pending presence
# to be sent out by user_id. Entries here get processed and put in
# pending_presence_by_dest
self.pending_presence = {}
LaterGauge(
"synapse_federation_transaction_queue_pending_pdus",
"",
[],
lambda: sum(
d.pending_pdu_count() for d in self._per_destination_queues.values()
),
)
LaterGauge(
"synapse_federation_transaction_queue_pending_edus",
"",
[],
lambda: sum(
d.pending_edu_count() for d in self._per_destination_queues.values()
),
)
self._order = 1
self._is_processing = False
self._last_poked_id = -1
self._processing_pending_presence = False
# map from room_id to a set of PerDestinationQueues which we believe are
# awaiting a call to flush_read_receipts_for_room. The presence of an entry
# here for a given room means that we are rate-limiting RR flushes to that room,
# and that there is a pending call to _flush_rrs_for_room in the system.
self._queues_awaiting_rr_flush_by_room = {
} # type: dict[str, set[PerDestinationQueue]]
self._rr_txn_interval_per_room_ms = (
1000.0 / hs.get_config().federation_rr_transactions_per_room_per_second
)
def _get_per_destination_queue(self, destination):
"""Get or create a PerDestinationQueue for the given destination
Args:
destination (str): server_name of remote server
Returns:
PerDestinationQueue
"""
queue = self._per_destination_queues.get(destination)
if not queue:
queue = PerDestinationQueue(self.hs, self._transaction_manager, destination)
self._per_destination_queues[destination] = queue
return queue
def notify_new_events(self, current_id):
"""This gets called when we have some new events we might want to
send out to other servers.
"""
self._last_poked_id = max(current_id, self._last_poked_id)
if self._is_processing:
return
# fire off a processing loop in the background
run_as_background_process(
"process_event_queue_for_federation",
self._process_event_queue_loop,
)
@defer.inlineCallbacks
def _process_event_queue_loop(self):
try:
self._is_processing = True
while True:
last_token = yield self.store.get_federation_out_pos("events")
next_token, events = yield self.store.get_all_new_events_stream(
last_token, self._last_poked_id, limit=100,
)
logger.debug("Handling %s -> %s", last_token, next_token)
if not events and next_token >= self._last_poked_id:
break
@defer.inlineCallbacks
def handle_event(event):
# Only send events for this server.
send_on_behalf_of = event.internal_metadata.get_send_on_behalf_of()
is_mine = self.is_mine_id(event.sender)
if not is_mine and send_on_behalf_of is None:
return
try:
# Get the state from before the event.
# We need to make sure that this is the state from before
# the event and not from after it.
# Otherwise if the last member on a server in a room is
# banned then it won't receive the event because it won't
# be in the room after the ban.
destinations = yield self.state.get_current_hosts_in_room(
event.room_id, latest_event_ids=event.prev_event_ids(),
)
except Exception:
logger.exception(
"Failed to calculate hosts in room for event: %s",
event.event_id,
)
return
destinations = set(destinations)
if send_on_behalf_of is not None:
# If we are sending the event on behalf of another server
# then it already has the event and there is no reason to
# send the event to it.
destinations.discard(send_on_behalf_of)
logger.debug("Sending %s to %r", event, destinations)
self._send_pdu(event, destinations)
@defer.inlineCallbacks
def handle_room_events(events):
for event in events:
yield handle_event(event)
events_by_room = {}
for event in events:
events_by_room.setdefault(event.room_id, []).append(event)
yield logcontext.make_deferred_yieldable(defer.gatherResults(
[
logcontext.run_in_background(handle_room_events, evs)
for evs in itervalues(events_by_room)
],
consumeErrors=True
))
yield self.store.update_federation_out_pos(
"events", next_token
)
if events:
now = self.clock.time_msec()
ts = yield self.store.get_received_ts(events[-1].event_id)
synapse.metrics.event_processing_lag.labels(
"federation_sender").set(now - ts)
synapse.metrics.event_processing_last_ts.labels(
"federation_sender").set(ts)
events_processed_counter.inc(len(events))
event_processing_loop_room_count.labels(
"federation_sender"
).inc(len(events_by_room))
event_processing_loop_counter.labels("federation_sender").inc()
synapse.metrics.event_processing_positions.labels(
"federation_sender").set(next_token)
finally:
self._is_processing = False
def _send_pdu(self, pdu, destinations):
# We loop through all destinations to see whether we already have
# a transaction in progress. If we do, stick it in the pending_pdus
# table and we'll get back to it later.
order = self._order
self._order += 1
destinations = set(destinations)
destinations.discard(self.server_name)
logger.debug("Sending to: %s", str(destinations))
if not destinations:
return
sent_pdus_destination_dist_total.inc(len(destinations))
sent_pdus_destination_dist_count.inc()
for destination in destinations:
self._get_per_destination_queue(destination).send_pdu(pdu, order)
@defer.inlineCallbacks
def send_read_receipt(self, receipt):
"""Send a RR to any other servers in the room
Args:
receipt (synapse.types.ReadReceipt): receipt to be sent
"""
# Some background on the rate-limiting going on here.
#
# It turns out that if we attempt to send out RRs as soon as we get them from
# a client, then we end up trying to do several hundred Hz of federation
# transactions. (The number of transactions scales as O(N^2) on the size of a
# room, since in a large room we have both more RRs coming in, and more servers
# to send them to.)
#
# This leads to a lot of CPU load, and we end up getting behind. The solution
# currently adopted is as follows:
#
# The first receipt in a given room is sent out immediately, at time T0. Any
# further receipts are, in theory, batched up for N seconds, where N is calculated
# based on the number of servers in the room to achieve a transaction frequency
# of around 50Hz. So, for example, if there were 100 servers in the room, then
# N would be 100 / 50Hz = 2 seconds.
#
# Then, after T+N, we flush out any receipts that have accumulated, and restart
# the timer to flush out more receipts at T+2N, etc. If no receipts accumulate,
# we stop the cycle and go back to the start.
#
# However, in practice, it is often possible to flush out receipts earlier: in
# particular, if we are sending a transaction to a given server anyway (for
# example, because we have a PDU or a RR in another room to send), then we may
# as well send out all of the pending RRs for that server. So it may be that
# by the time we get to T+N, we don't actually have any RRs left to send out.
# Nevertheless we continue to buffer up RRs for the room in question until we
# reach the point that no RRs arrive between timer ticks.
#
# For even more background, see https://github.com/matrix-org/synapse/issues/4730.
room_id = receipt.room_id
# Work out which remote servers should be poked and poke them.
domains = yield self.state.get_current_hosts_in_room(room_id)
domains = [d for d in domains if d != self.server_name]
if not domains:
return
queues_pending_flush = self._queues_awaiting_rr_flush_by_room.get(
room_id
)
# if there is no flush yet scheduled, we will send out these receipts with
# immediate flushes, and schedule the next flush for this room.
if queues_pending_flush is not None:
logger.debug("Queuing receipt for: %r", domains)
else:
logger.debug("Sending receipt to: %r", domains)
self._schedule_rr_flush_for_room(room_id, len(domains))
for domain in domains:
queue = self._get_per_destination_queue(domain)
queue.queue_read_receipt(receipt)
# if there is already a RR flush pending for this room, then make sure this
# destination is registered for the flush
if queues_pending_flush is not None:
queues_pending_flush.add(queue)
else:
queue.flush_read_receipts_for_room(room_id)
def _schedule_rr_flush_for_room(self, room_id, n_domains):
# that is going to cause approximately len(domains) transactions, so now back
# off for that multiplied by RR_TXN_INTERVAL_PER_ROOM
backoff_ms = self._rr_txn_interval_per_room_ms * n_domains
logger.debug("Scheduling RR flush in %s in %d ms", room_id, backoff_ms)
self.clock.call_later(backoff_ms, self._flush_rrs_for_room, room_id)
self._queues_awaiting_rr_flush_by_room[room_id] = set()
def _flush_rrs_for_room(self, room_id):
queues = self._queues_awaiting_rr_flush_by_room.pop(room_id)
logger.debug("Flushing RRs in %s to %s", room_id, queues)
if not queues:
# no more RRs arrived for this room; we are done.
return
# schedule the next flush
self._schedule_rr_flush_for_room(room_id, len(queues))
for queue in queues:
queue.flush_read_receipts_for_room(room_id)
@logcontext.preserve_fn # the caller should not yield on this
@defer.inlineCallbacks
def send_presence(self, states):
"""Send the new presence states to the appropriate destinations.
This actually queues up the presence states ready for sending and
triggers a background task to process them and send out the transactions.
Args:
states (list(UserPresenceState))
"""
if not self.hs.config.use_presence:
# No-op if presence is disabled.
return
# First we queue up the new presence by user ID, so multiple presence
# updates in quick successtion are correctly handled
# We only want to send presence for our own users, so lets always just
# filter here just in case.
self.pending_presence.update({
state.user_id: state for state in states
if self.is_mine_id(state.user_id)
})
# We then handle the new pending presence in batches, first figuring
# out the destinations we need to send each state to and then poking it
# to attempt a new transaction. We linearize this so that we don't
# accidentally mess up the ordering and send multiple presence updates
# in the wrong order
if self._processing_pending_presence:
return
self._processing_pending_presence = True
try:
while True:
states_map = self.pending_presence
self.pending_presence = {}
if not states_map:
break
yield self._process_presence_inner(list(states_map.values()))
except Exception:
logger.exception("Error sending presence states to servers")
finally:
self._processing_pending_presence = False
@measure_func("txnqueue._process_presence")
@defer.inlineCallbacks
def _process_presence_inner(self, states):
"""Given a list of states populate self.pending_presence_by_dest and
poke to send a new transaction to each destination
Args:
states (list(UserPresenceState))
"""
hosts_and_states = yield get_interested_remotes(self.store, states, self.state)
for destinations, states in hosts_and_states:
for destination in destinations:
if destination == self.server_name:
continue
self._get_per_destination_queue(destination).send_presence(states)
def build_and_send_edu(self, destination, edu_type, content, key=None):
"""Construct an Edu object, and queue it for sending
Args:
destination (str): name of server to send to
edu_type (str): type of EDU to send
content (dict): content of EDU
key (Any|None): clobbering key for this edu
"""
if destination == self.server_name:
logger.info("Not sending EDU to ourselves")
return
edu = Edu(
origin=self.server_name,
destination=destination,
edu_type=edu_type,
content=content,
)
self.send_edu(edu, key)
def send_edu(self, edu, key):
"""Queue an EDU for sending
Args:
edu (Edu): edu to send
key (Any|None): clobbering key for this edu
"""
queue = self._get_per_destination_queue(edu.destination)
if key:
queue.send_keyed_edu(edu, key)
else:
queue.send_edu(edu)
def send_device_messages(self, destination):
if destination == self.server_name:
logger.info("Not sending device update to ourselves")
return
self._get_per_destination_queue(destination).attempt_new_transaction()
def get_current_token(self):
return 0