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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 collections import OrderedDict
- from typing import TYPE_CHECKING, Dict, Hashable, Iterable, List, Optional, Set, Tuple
- import attr
- from prometheus_client import Counter
- from typing_extensions import Literal
- 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,
- wrap_as_background_process,
- )
- from synapse.types import JsonDict, ReadReceipt, RoomStreamToken
- from synapse.util import Clock
- 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()
- @attr.s
- class _PresenceQueue:
- """A queue of destinations that need to be woken up due to new presence
- updates.
- Staggers waking up of per destination queues to ensure that we don't attempt
- to start TLS connections with many hosts all at once, leading to pinned CPU.
- """
- # The maximum duration in seconds between queuing up a destination and it
- # being woken up.
- _MAX_TIME_IN_QUEUE = 30.0
- # The maximum duration in seconds between waking up consecutive destination
- # queues.
- _MAX_DELAY = 0.1
- sender: "FederationSender" = attr.ib()
- clock: Clock = attr.ib()
- queue: "OrderedDict[str, Literal[None]]" = attr.ib(factory=OrderedDict)
- processing: bool = attr.ib(default=False)
- def add_to_queue(self, destination: str) -> None:
- """Add a destination to the queue to be woken up."""
- self.queue[destination] = None
- if not self.processing:
- self._handle()
- @wrap_as_background_process("_PresenceQueue.handle")
- async def _handle(self) -> None:
- """Background process to drain the queue."""
- if not self.queue:
- return
- assert not self.processing
- self.processing = True
- try:
- # We start with a delay that should drain the queue quickly enough that
- # we process all destinations in the queue in _MAX_TIME_IN_QUEUE
- # seconds.
- #
- # We also add an upper bound to the delay, to gracefully handle the
- # case where the queue only has a few entries in it.
- current_sleep_seconds = min(
- self._MAX_DELAY, self._MAX_TIME_IN_QUEUE / len(self.queue)
- )
- while self.queue:
- destination, _ = self.queue.popitem(last=False)
- queue = self.sender._get_per_destination_queue(destination)
- if not queue._new_data_to_send:
- # The per destination queue has already been woken up.
- continue
- queue.attempt_new_transaction()
- await self.clock.sleep(current_sleep_seconds)
- if not self.queue:
- break
- # More destinations may have been added to the queue, so we may
- # need to reduce the delay to ensure everything gets processed
- # within _MAX_TIME_IN_QUEUE seconds.
- current_sleep_seconds = min(
- current_sleep_seconds, self._MAX_TIME_IN_QUEUE / len(self.queue)
- )
- finally:
- self.processing = False
- 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: Optional["PresenceRouter"] = None
- 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: 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: 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()
- self._presence_queue = _PresenceQueue(self, self.clock)
- 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: Optional[Set[str]] = None
- 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: 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, start_loop=False
- )
- self._presence_queue.add_to_queue(destination)
- 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: Optional[str] = None
- 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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