# Copyright 2014-2016 OpenMarket Ltd # Copyright 2019 New Vector Ltd # Copyright 2021 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 datetime import logging from types import TracebackType from typing import TYPE_CHECKING, Dict, Hashable, Iterable, List, Optional, Tuple, Type import attr from prometheus_client import Counter from synapse.api.constants import EduTypes from synapse.api.errors import ( FederationDeniedError, HttpResponseException, RequestSendFailed, ) from synapse.api.presence import UserPresenceState from synapse.events import EventBase from synapse.federation.units import Edu from synapse.handlers.presence import format_user_presence_state from synapse.logging import issue9533_logger from synapse.logging.tracing import SynapseTags, set_attribute from synapse.metrics import sent_transactions_counter from synapse.metrics.background_process_metrics import run_as_background_process from synapse.types import ReadReceipt from synapse.util.retryutils import NotRetryingDestination, get_retry_limiter from synapse.visibility import filter_events_for_server if TYPE_CHECKING: import synapse.server # This is defined in the Matrix spec and enforced by the receiver. MAX_EDUS_PER_TRANSACTION = 100 logger = logging.getLogger(__name__) sent_edus_counter = Counter( "synapse_federation_client_sent_edus", "Total number of EDUs successfully sent" ) sent_edus_by_type = Counter( "synapse_federation_client_sent_edus_by_type", "Number of sent EDUs successfully sent, by event type", ["type"], ) class PerDestinationQueue: """ Manages the per-destination transmission queues. Args: hs transaction_sender destination: the server_name of the destination that we are managing transmission for. """ def __init__( self, hs: "synapse.server.HomeServer", transaction_manager: "synapse.federation.sender.TransactionManager", destination: str, ): self._server_name = hs.hostname self._clock = hs.get_clock() self._storage_controllers = hs.get_storage_controllers() self._store = hs.get_datastores().main self._transaction_manager = transaction_manager self._instance_name = hs.get_instance_name() self._federation_shard_config = hs.config.worker.federation_shard_config self._state = hs.get_state_handler() self._should_send_on_this_instance = True if not self._federation_shard_config.should_handle( self._instance_name, destination ): # We don't raise an exception here to avoid taking out any other # processing. We have a guard in `attempt_new_transaction` that # ensure we don't start sending stuff. logger.error( "Create a per destination queue for %s on wrong worker", destination, ) self._should_send_on_this_instance = False self._destination = destination self.transmission_loop_running = False # Flag to signal to any running transmission loop that there is new data # queued up to be sent. self._new_data_to_send = False # True whilst we are sending events that the remote homeserver missed # because it was unreachable. We start in this state so we can perform # catch-up at startup. # New events will only be sent once this is finished, at which point # _catching_up is flipped to False. self._catching_up: bool = True # The stream_ordering of the most recent PDU that was discarded due to # being in catch-up mode. self._catchup_last_skipped: int = 0 # Cache of the last successfully-transmitted stream ordering for this # destination (we are the only updater so this is safe) self._last_successful_stream_ordering: Optional[int] = None # a queue of pending PDUs self._pending_pdus: List[EventBase] = [] # XXX this is never actually used: see # https://github.com/matrix-org/synapse/issues/7549 self._pending_edus: List[Edu] = [] # Pending EDUs by their "key". Keyed EDUs are EDUs that get clobbered # based on their key (e.g. typing events by room_id) # Map of (edu_type, key) -> Edu self._pending_edus_keyed: Dict[Tuple[str, Hashable], Edu] = {} # Map of user_id -> UserPresenceState of pending presence to be sent to this # destination self._pending_presence: Dict[str, UserPresenceState] = {} # room_id -> receipt_type -> user_id -> receipt_dict self._pending_rrs: Dict[str, Dict[str, Dict[str, dict]]] = {} self._rrs_pending_flush = False # stream_id of last successfully sent to-device message. # NB: may be a long or an int. self._last_device_stream_id = 0 # stream_id of last successfully sent device list update. self._last_device_list_stream_id = 0 def __str__(self) -> str: return "PerDestinationQueue[%s]" % self._destination def pending_pdu_count(self) -> int: return len(self._pending_pdus) def pending_edu_count(self) -> int: return ( len(self._pending_edus) + len(self._pending_presence) + len(self._pending_edus_keyed) ) def send_pdu(self, pdu: EventBase) -> None: """Add a PDU to the queue, and start the transmission loop if necessary Args: pdu: pdu to send """ if not self._catching_up or self._last_successful_stream_ordering is None: # only enqueue the PDU if we are not catching up (False) or do not # yet know if we have anything to catch up (None) self._pending_pdus.append(pdu) else: assert pdu.internal_metadata.stream_ordering self._catchup_last_skipped = pdu.internal_metadata.stream_ordering self.attempt_new_transaction() def send_presence( self, states: Iterable[UserPresenceState], start_loop: bool = True ) -> None: """Add presence updates to the queue. Args: states: Presence updates to send start_loop: Whether to start the transmission loop if not already running. Args: states: presence to send """ self._pending_presence.update({state.user_id: state for state in states}) self._new_data_to_send = True if start_loop: self.attempt_new_transaction() def queue_read_receipt(self, receipt: ReadReceipt) -> None: """Add a RR to the list to be sent. Doesn't start the transmission loop yet (see flush_read_receipts_for_room) Args: receipt: receipt to be queued """ self._pending_rrs.setdefault(receipt.room_id, {}).setdefault( receipt.receipt_type, {} )[receipt.user_id] = {"event_ids": receipt.event_ids, "data": receipt.data} def flush_read_receipts_for_room(self, room_id: str) -> None: # if we don't have any read-receipts for this room, it may be that we've already # sent them out, so we don't need to flush. if room_id not in self._pending_rrs: return self._rrs_pending_flush = True self.attempt_new_transaction() def send_keyed_edu(self, edu: Edu, key: Hashable) -> None: self._pending_edus_keyed[(edu.edu_type, key)] = edu self.attempt_new_transaction() def send_edu(self, edu: Edu) -> None: self._pending_edus.append(edu) self.attempt_new_transaction() def mark_new_data(self) -> None: """Marks that the destination has new data to send, without starting a new transaction. If a transaction loop is already in progress then a new transaction will be attempted when the current one finishes. """ self._new_data_to_send = True def attempt_new_transaction(self) -> None: """Try to start a new transaction to this destination If there is already a transaction in progress to this destination, returns immediately. Otherwise kicks off the process of sending a transaction in the background. """ # Mark that we (may) have new things to send, so that any running # transmission loop will recheck whether there is stuff to send. self._new_data_to_send = True if self.transmission_loop_running: # XXX: this can get stuck on by a never-ending # request at which point pending_pdus just keeps growing. # we need application-layer timeouts of some flavour of these # requests logger.debug("TX [%s] Transaction already in progress", self._destination) return if not self._should_send_on_this_instance: # We don't raise an exception here to avoid taking out any other # processing. logger.error( "Trying to start a transaction to %s on wrong worker", self._destination ) return logger.debug("TX [%s] Starting transaction loop", self._destination) run_as_background_process( "federation_transaction_transmission_loop", self._transaction_transmission_loop, ) async def _transaction_transmission_loop(self) -> None: pending_pdus: List[EventBase] = [] try: self.transmission_loop_running = True # This will throw if we wouldn't retry. We do this here so we fail # quickly, but we will later check this again in the http client, # hence why we throw the result away. await get_retry_limiter(self._destination, self._clock, self._store) if self._catching_up: # we potentially need to catch-up first await self._catch_up_transmission_loop() if self._catching_up: # not caught up yet return pending_pdus = [] while True: self._new_data_to_send = False async with _TransactionQueueManager(self) as ( pending_pdus, pending_edus, ): if not pending_pdus and not pending_edus: logger.debug("TX [%s] Nothing to send", self._destination) # If we've gotten told about new things to send during # checking for things to send, we try looking again. # Otherwise new PDUs or EDUs might arrive in the meantime, # but not get sent because we hold the # `transmission_loop_running` flag. if self._new_data_to_send: continue else: return if pending_pdus: logger.debug( "TX [%s] len(pending_pdus_by_dest[dest]) = %d", self._destination, len(pending_pdus), ) await self._transaction_manager.send_new_transaction( self._destination, pending_pdus, pending_edus ) sent_transactions_counter.inc() sent_edus_counter.inc(len(pending_edus)) for edu in pending_edus: sent_edus_by_type.labels(edu.edu_type).inc() except NotRetryingDestination as e: logger.debug( "TX [%s] not ready for retry yet (next retry at %s) - " "dropping transaction for now", self._destination, datetime.datetime.fromtimestamp( (e.retry_last_ts + e.retry_interval) / 1000.0 ), ) if e.retry_interval > 60 * 60 * 1000: # we won't retry for another hour! # (this suggests a significant outage) # We drop pending EDUs because otherwise they will # rack up indefinitely. # (Dropping PDUs is already performed by `_start_catching_up`.) # Note that: # - the EDUs that are being dropped here are those that we can # afford to drop (specifically, only typing notifications, # read receipts and presence updates are being dropped here) # - Other EDUs such as to_device messages are queued with a # different mechanism # - this is all volatile state that would be lost if the # federation sender restarted anyway # dropping read receipts is a bit sad but should be solved # through another mechanism, because this is all volatile! self._pending_edus = [] self._pending_edus_keyed = {} self._pending_presence = {} self._pending_rrs = {} self._start_catching_up() except FederationDeniedError as e: logger.info(e) except HttpResponseException as e: logger.warning( "TX [%s] Received %d response to transaction: %s", self._destination, e.code, e, ) except RequestSendFailed as e: logger.warning( "TX [%s] Failed to send transaction: %s", self._destination, e ) for p in pending_pdus: logger.info( "Failed to send event %s to %s", p.event_id, self._destination ) except Exception: logger.exception("TX [%s] Failed to send transaction", self._destination) for p in pending_pdus: logger.info( "Failed to send event %s to %s", p.event_id, self._destination ) finally: # We want to be *very* sure we clear this after we stop processing self.transmission_loop_running = False async def _catch_up_transmission_loop(self) -> None: first_catch_up_check = self._last_successful_stream_ordering is None if first_catch_up_check: # first catchup so get last_successful_stream_ordering from database self._last_successful_stream_ordering = ( await self._store.get_destination_last_successful_stream_ordering( self._destination ) ) _tmp_last_successful_stream_ordering = self._last_successful_stream_ordering if _tmp_last_successful_stream_ordering is None: # if it's still None, then this means we don't have the information # in our database ­ we haven't successfully sent a PDU to this server # (at least since the introduction of the feature tracking # last_successful_stream_ordering). # Sadly, this means we can't do anything here as we don't know what # needs catching up — so catching up is futile; let's stop. self._catching_up = False return last_successful_stream_ordering: int = _tmp_last_successful_stream_ordering # get at most 50 catchup room/PDUs while True: event_ids = await self._store.get_catch_up_room_event_ids( self._destination, last_successful_stream_ordering ) if not event_ids: # No more events to catch up on, but we can't ignore the chance # of a race condition, so we check that no new events have been # skipped due to us being in catch-up mode if self._catchup_last_skipped > last_successful_stream_ordering: # another event has been skipped because we were in catch-up mode continue # we are done catching up! self._catching_up = False break if first_catch_up_check: # as this is our check for needing catch-up, we may have PDUs in # the queue from before we *knew* we had to do catch-up, so # clear those out now. self._start_catching_up() # fetch the relevant events from the event store # - redacted behaviour of REDACT is fine, since we only send metadata # of redacted events to the destination. # - don't need to worry about rejected events as we do not actively # forward received events over federation. catchup_pdus = await self._store.get_events_as_list(event_ids) if not catchup_pdus: raise AssertionError( "No events retrieved when we asked for %r. " "This should not happen." % event_ids ) logger.info( "Catching up destination %s with %d PDUs", self._destination, len(catchup_pdus), ) # We send transactions with events from one room only, as its likely # that the remote will have to do additional processing, which may # take some time. It's better to give it small amounts of work # rather than risk the request timing out and repeatedly being # retried, and not making any progress. # # Note: `catchup_pdus` will have exactly one PDU per room. for pdu in catchup_pdus: # The PDU from the DB will be the last PDU in the room from # *this server* that wasn't sent to the remote. However, other # servers may have sent lots of events since then, and we want # to try and tell the remote only about the *latest* events in # the room. This is so that it doesn't get inundated by events # from various parts of the DAG, which all need to be processed. # # Note: this does mean that in large rooms a server coming back # online will get sent the same events from all the different # servers, but the remote will correctly deduplicate them and # handle it only once. # Step 1, fetch the current extremities extrems = await self._store.get_prev_events_for_room(pdu.room_id) if pdu.event_id in extrems: # If the event is in the extremities, then great! We can just # use that without having to do further checks. room_catchup_pdus = [pdu] else: # If not, fetch the extremities and figure out which we can # send. extrem_events = await self._store.get_events_as_list(extrems) new_pdus = [] for p in extrem_events: # We pulled this from the DB, so it'll be non-null assert p.internal_metadata.stream_ordering # Filter out events that happened before the remote went # offline if ( p.internal_metadata.stream_ordering < last_successful_stream_ordering ): continue new_pdus.append(p) # Filter out events where the server is not in the room, # e.g. it may have left/been kicked. *Ideally* we'd pull # out the kick and send that, but it's a rare edge case # so we don't bother for now (the server that sent the # kick should send it out if its online). new_pdus = await filter_events_for_server( self._storage_controllers, self._destination, new_pdus, redact=False, ) # If we've filtered out all the extremities, fall back to # sending the original event. This should ensure that the # server gets at least some of missed events (especially if # the other sending servers are up). if new_pdus: room_catchup_pdus = new_pdus else: room_catchup_pdus = [pdu] logger.info( "Catching up rooms to %s: %r", self._destination, pdu.room_id ) await self._transaction_manager.send_new_transaction( self._destination, room_catchup_pdus, [] ) sent_transactions_counter.inc() # We pulled this from the DB, so it'll be non-null assert pdu.internal_metadata.stream_ordering # Note that we mark the last successful stream ordering as that # from the *original* PDU, rather than the PDU(s) we actually # send. This is because we use it to mark our position in the # queue of missed PDUs to process. last_successful_stream_ordering = pdu.internal_metadata.stream_ordering self._last_successful_stream_ordering = last_successful_stream_ordering await self._store.set_destination_last_successful_stream_ordering( self._destination, last_successful_stream_ordering ) def _get_rr_edus(self, force_flush: bool) -> Iterable[Edu]: if not self._pending_rrs: return if not force_flush and not self._rrs_pending_flush: # not yet time for this lot return edu = Edu( origin=self._server_name, destination=self._destination, edu_type=EduTypes.RECEIPT, content=self._pending_rrs, ) self._pending_rrs = {} self._rrs_pending_flush = False yield edu def _pop_pending_edus(self, limit: int) -> List[Edu]: pending_edus = self._pending_edus pending_edus, self._pending_edus = pending_edus[:limit], pending_edus[limit:] return pending_edus async def _get_device_update_edus(self, limit: int) -> Tuple[List[Edu], int]: last_device_list = self._last_device_list_stream_id # Retrieve list of new device updates to send to the destination now_stream_id, results = await self._store.get_device_updates_by_remote( self._destination, last_device_list, limit=limit ) edus = [ Edu( origin=self._server_name, destination=self._destination, edu_type=edu_type, content=content, ) for (edu_type, content) in results ] assert len(edus) <= limit, "get_device_updates_by_remote returned too many EDUs" return edus, now_stream_id async def _get_to_device_message_edus(self, limit: int) -> Tuple[List[Edu], int]: last_device_stream_id = self._last_device_stream_id to_device_stream_id = self._store.get_to_device_stream_token() contents, stream_id = await self._store.get_new_device_msgs_for_remote( self._destination, last_device_stream_id, to_device_stream_id, limit ) for content in contents: message_id = content.get("message_id") if not message_id: continue set_attribute(SynapseTags.TO_DEVICE_MESSAGE_ID, message_id) edus = [ Edu( origin=self._server_name, destination=self._destination, edu_type=EduTypes.DIRECT_TO_DEVICE, content=content, ) for content in contents ] if edus: issue9533_logger.debug( "Sending %i to-device messages to %s, up to stream id %i", len(edus), self._destination, stream_id, ) return edus, stream_id def _start_catching_up(self) -> None: """ Marks this destination as being in catch-up mode. This throws away the PDU queue. """ self._catching_up = True self._pending_pdus = [] @attr.s(slots=True, auto_attribs=True) class _TransactionQueueManager: """A helper async context manager for pulling stuff off the queues and tracking what was last successfully sent, etc. """ queue: PerDestinationQueue _device_stream_id: Optional[int] = None _device_list_id: Optional[int] = None _last_stream_ordering: Optional[int] = None _pdus: List[EventBase] = attr.Factory(list) async def __aenter__(self) -> Tuple[List[EventBase], List[Edu]]: # First we calculate the EDUs we want to send, if any. # We start by fetching device related EDUs, i.e device updates and to # device messages. We have to keep 2 free slots for presence and rr_edus. device_edu_limit = MAX_EDUS_PER_TRANSACTION - 2 # We prioritize to-device messages so that existing encryption channels # work. We also keep a few slots spare (by reducing the limit) so that # we can still trickle out some device list updates. ( to_device_edus, device_stream_id, ) = await self.queue._get_to_device_message_edus(device_edu_limit - 10) if to_device_edus: self._device_stream_id = device_stream_id else: self.queue._last_device_stream_id = device_stream_id device_edu_limit -= len(to_device_edus) device_update_edus, dev_list_id = await self.queue._get_device_update_edus( device_edu_limit ) if device_update_edus: self._device_list_id = dev_list_id else: self.queue._last_device_list_stream_id = dev_list_id pending_edus = device_update_edus + to_device_edus # Now add the read receipt EDU. pending_edus.extend(self.queue._get_rr_edus(force_flush=False)) # And presence EDU. if self.queue._pending_presence: pending_edus.append( Edu( origin=self.queue._server_name, destination=self.queue._destination, edu_type=EduTypes.PRESENCE, content={ "push": [ format_user_presence_state( presence, self.queue._clock.time_msec() ) for presence in self.queue._pending_presence.values() ] }, ) ) self.queue._pending_presence = {} # Finally add any other types of EDUs if there is room. pending_edus.extend( self.queue._pop_pending_edus(MAX_EDUS_PER_TRANSACTION - len(pending_edus)) ) while ( len(pending_edus) < MAX_EDUS_PER_TRANSACTION and self.queue._pending_edus_keyed ): _, val = self.queue._pending_edus_keyed.popitem() pending_edus.append(val) # Now we look for any PDUs to send, by getting up to 50 PDUs from the # queue self._pdus = self.queue._pending_pdus[:50] if not self._pdus and not pending_edus: return [], [] # if we've decided to send a transaction anyway, and we have room, we # may as well send any pending RRs if len(pending_edus) < MAX_EDUS_PER_TRANSACTION: pending_edus.extend(self.queue._get_rr_edus(force_flush=True)) if self._pdus: self._last_stream_ordering = self._pdus[ -1 ].internal_metadata.stream_ordering assert self._last_stream_ordering return self._pdus, pending_edus async def __aexit__( self, exc_type: Optional[Type[BaseException]], exc: Optional[BaseException], tb: Optional[TracebackType], ) -> None: if exc_type is not None: # Failed to send transaction, so we bail out. return # Successfully sent transactions, so we remove pending PDUs from the queue if self._pdus: self.queue._pending_pdus = self.queue._pending_pdus[len(self._pdus) :] # Succeeded to send the transaction so we record where we have sent up # to in the various streams if self._device_stream_id: await self.queue._store.delete_device_msgs_for_remote( self.queue._destination, self._device_stream_id ) self.queue._last_device_stream_id = self._device_stream_id # also mark the device updates as sent if self._device_list_id: logger.info( "Marking as sent %r %r", self.queue._destination, self._device_list_id ) await self.queue._store.mark_as_sent_devices_by_remote( self.queue._destination, self._device_list_id ) self.queue._last_device_list_stream_id = self._device_list_id if self._last_stream_ordering: # we sent some PDUs and it was successful, so update our # last_successful_stream_ordering in the destinations table. await self.queue._store.set_destination_last_successful_stream_ordering( self.queue._destination, self._last_stream_ordering )