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synapse-old/synapse/federation/sender/__init__.py

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# 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 abc
import logging
from typing import TYPE_CHECKING, Dict, Hashable, Iterable, List, Optional, Set, Tuple
from prometheus_client import Counter
from twisted.internet import defer
import synapse.metrics
from synapse.api.presence import UserPresenceState
from synapse.events import EventBase
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.logging.context import make_deferred_yieldable, run_in_background
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.types import JsonDict, ReadReceipt, RoomStreamToken
from synapse.util.metrics import Measure
if TYPE_CHECKING:
from synapse.events.presence_router import PresenceRouter
from synapse.server import HomeServer
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",
)
# Time (in s) after Synapse's startup that we will begin to wake up destinations
# that have catch-up outstanding.
CATCH_UP_STARTUP_DELAY_SEC = 15
# Time (in s) to wait in between waking up each destination, i.e. one destination
# will be woken up every <x> seconds after Synapse's startup until we have woken
# every destination has outstanding catch-up.
CATCH_UP_STARTUP_INTERVAL_SEC = 5
class AbstractFederationSender(metaclass=abc.ABCMeta):
@abc.abstractmethod
def notify_new_events(self, max_token: RoomStreamToken) -> None:
"""This gets called when we have some new events we might want to
send out to other servers.
"""
raise NotImplementedError()
@abc.abstractmethod
async def send_read_receipt(self, receipt: ReadReceipt) -> None:
"""Send a RR to any other servers in the room
Args:
receipt: receipt to be sent
"""
raise NotImplementedError()
@abc.abstractmethod
def send_presence_to_destinations(
self, states: Iterable[UserPresenceState], destinations: Iterable[str]
) -> None:
"""Send the given presence states to the given destinations.
Args:
destinations:
"""
raise NotImplementedError()
@abc.abstractmethod
def build_and_send_edu(
self,
destination: str,
edu_type: str,
content: JsonDict,
key: Optional[Hashable] = None,
) -> None:
"""Construct an Edu object, and queue it for sending
Args:
destination: name of server to send to
edu_type: type of EDU to send
content: content of EDU
key: clobbering key for this edu
"""
raise NotImplementedError()
@abc.abstractmethod
def send_device_messages(self, destination: str) -> None:
raise NotImplementedError()
@abc.abstractmethod
def wake_destination(self, destination: str) -> None:
"""Called when we want to retry sending transactions to a remote.
This is mainly useful if the remote server has been down and we think it
might have come back.
"""
raise NotImplementedError()
@abc.abstractmethod
def get_current_token(self) -> int:
raise NotImplementedError()
@abc.abstractmethod
def federation_ack(self, instance_name: str, token: int) -> None:
raise NotImplementedError()
@abc.abstractmethod
async def get_replication_rows(
self, instance_name: str, from_token: int, to_token: int, target_row_count: int
) -> Tuple[List[Tuple[int, Tuple]], int, bool]:
raise NotImplementedError()
class FederationSender(AbstractFederationSender):
def __init__(self, hs: "HomeServer"):
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._presence_router = None # type: Optional[PresenceRouter]
self._transaction_manager = TransactionManager(hs)
self._instance_name = hs.get_instance_name()
self._federation_shard_config = hs.config.worker.federation_shard_config
# 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
),
)
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._is_processing = False
self._last_poked_id = -1
# 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.config.federation_rr_transactions_per_room_per_second
)
# wake up destinations that have outstanding PDUs to be caught up
self._catchup_after_startup_timer = self.clock.call_later(
CATCH_UP_STARTUP_DELAY_SEC,
run_as_background_process,
"wake_destinations_needing_catchup",
self._wake_destinations_needing_catchup,
)
self._external_cache = hs.get_external_cache()
def _get_per_destination_queue(self, destination: str) -> PerDestinationQueue:
"""Get or create a PerDestinationQueue for the given destination
Args:
destination: server_name of remote server
"""
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, max_token: RoomStreamToken) -> None:
"""This gets called when we have some new events we might want to
send out to other servers.
"""
# We just use the minimum stream ordering and ignore the vector clock
# component. This is safe to do as long as we *always* ignore the vector
# clock components.
current_id = max_token.stream
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
)
async def _process_event_queue_loop(self) -> None:
try:
self._is_processing = True
while True:
last_token = await self.store.get_federation_out_pos("events")
next_token, events = await 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
async def handle_event(event: EventBase) -> None:
# 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
if not event.internal_metadata.should_proactively_send():
return
destinations = None # type: Optional[Set[str]]
if not event.prev_event_ids():
# If there are no prev event IDs then the state is empty
# and so no remote servers in the room
destinations = set()
else:
# We check the external cache for the destinations, which is
# stored per state group.
sg = await self._external_cache.get(
"event_to_prev_state_group", event.event_id
)
if sg:
destinations = await self._external_cache.get(
"get_joined_hosts", str(sg)
)
if destinations is None:
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 = await self.state.get_hosts_in_room_at_events(
event.room_id, event_ids=event.prev_event_ids()
)
except Exception:
logger.exception(
"Failed to calculate hosts in room for event: %s",
event.event_id,
)
return
destinations = {
d
for d in destinations
if self._federation_shard_config.should_handle(
self._instance_name, d
)
}
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)
if destinations:
await self._send_pdu(event, destinations)
now = self.clock.time_msec()
ts = await self.store.get_received_ts(event.event_id)
synapse.metrics.event_processing_lag_by_event.labels(
"federation_sender"
).observe((now - ts) / 1000)
async def handle_room_events(events: Iterable[EventBase]) -> None:
with Measure(self.clock, "handle_room_events"):
for event in events:
await handle_event(event)
events_by_room = {} # type: Dict[str, List[EventBase]]
for event in events:
events_by_room.setdefault(event.room_id, []).append(event)
await make_deferred_yieldable(
defer.gatherResults(
[
run_in_background(handle_room_events, evs)
for evs in events_by_room.values()
],
consumeErrors=True,
)
)
await self.store.update_federation_out_pos("events", next_token)
if events:
now = self.clock.time_msec()
ts = await 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
async def _send_pdu(self, pdu: EventBase, destinations: Iterable[str]) -> None:
# 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.
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()
assert pdu.internal_metadata.stream_ordering
# track the fact that we have a PDU for these destinations,
# to allow us to perform catch-up later on if the remote is unreachable
# for a while.
await self.store.store_destination_rooms_entries(
destinations,
pdu.room_id,
pdu.internal_metadata.stream_ordering,
)
for destination in destinations:
self._get_per_destination_queue(destination).send_pdu(pdu)
async def send_read_receipt(self, receipt: ReadReceipt) -> None:
"""Send a RR to any other servers in the room
Args:
receipt: 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_set = await self.state.get_current_hosts_in_room(room_id)
domains = [
d
for d in domains_set
if d != self.server_name
and self._federation_shard_config.should_handle(self._instance_name, d)
]
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: str, n_domains: int) -> None:
# 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: str) -> None:
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)
def send_presence_to_destinations(
self, states: Iterable[UserPresenceState], destinations: Iterable[str]
) -> None:
"""Send the given presence states to the given destinations.
destinations (list[str])
"""
if not states or not self.hs.config.use_presence:
# No-op if presence is disabled.
return
# Ensure we only send out presence states for local users.
for state in states:
assert self.is_mine_id(state.user_id)
for destination in destinations:
if destination == self.server_name:
continue
if not self._federation_shard_config.should_handle(
self._instance_name, destination
):
continue
self._get_per_destination_queue(destination).send_presence(states)
def build_and_send_edu(
self,
destination: str,
edu_type: str,
content: JsonDict,
key: Optional[Hashable] = None,
) -> None:
"""Construct an Edu object, and queue it for sending
Args:
destination: name of server to send to
edu_type: type of EDU to send
content: content of EDU
key: clobbering key for this edu
"""
if destination == self.server_name:
logger.info("Not sending EDU to ourselves")
return
if not self._federation_shard_config.should_handle(
self._instance_name, destination
):
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: Edu, key: Optional[Hashable]) -> None:
"""Queue an EDU for sending
Args:
edu: edu to send
key: clobbering key for this edu
"""
if not self._federation_shard_config.should_handle(
self._instance_name, edu.destination
):
return
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: str) -> None:
if destination == self.server_name:
logger.warning("Not sending device update to ourselves")
return
if not self._federation_shard_config.should_handle(
self._instance_name, destination
):
return
self._get_per_destination_queue(destination).attempt_new_transaction()
def wake_destination(self, destination: str) -> None:
"""Called when we want to retry sending transactions to a remote.
This is mainly useful if the remote server has been down and we think it
might have come back.
"""
if destination == self.server_name:
logger.warning("Not waking up ourselves")
return
if not self._federation_shard_config.should_handle(
self._instance_name, destination
):
return
self._get_per_destination_queue(destination).attempt_new_transaction()
@staticmethod
def get_current_token() -> int:
# Dummy implementation for case where federation sender isn't offloaded
# to a worker.
return 0
def federation_ack(self, instance_name: str, token: int) -> None:
# It is not expected that this gets called on FederationSender.
raise NotImplementedError()
@staticmethod
async def get_replication_rows(
instance_name: str, from_token: int, to_token: int, target_row_count: int
) -> Tuple[List[Tuple[int, Tuple]], int, bool]:
# Dummy implementation for case where federation sender isn't offloaded
# to a worker.
return [], 0, False
async def _wake_destinations_needing_catchup(self) -> None:
"""
Wakes up destinations that need catch-up and are not currently being
backed off from.
In order to reduce load spikes, adds a delay between each destination.
"""
last_processed = None # type: Optional[str]
while True:
destinations_to_wake = (
await self.store.get_catch_up_outstanding_destinations(last_processed)
)
if not destinations_to_wake:
# finished waking all destinations!
self._catchup_after_startup_timer = None
break
last_processed = destinations_to_wake[-1]
destinations_to_wake = [
d
for d in destinations_to_wake
if self._federation_shard_config.should_handle(self._instance_name, d)
]
for destination in destinations_to_wake:
logger.info(
"Destination %s has outstanding catch-up, waking up.",
last_processed,
)
self.wake_destination(destination)
await self.clock.sleep(CATCH_UP_STARTUP_INTERVAL_SEC)
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