diff --git a/synapse/handlers/federation.py b/synapse/handlers/federation.py
index ed0fa51e7f..53f9296399 100644
--- a/synapse/handlers/federation.py
+++ b/synapse/handlers/federation.py
@@ -14,6 +14,7 @@
# limitations under the License.
"""Contains handlers for federation events."""
+import synapse.util.logcontext
from signedjson.key import decode_verify_key_bytes
from signedjson.sign import verify_signed_json
from unpaddedbase64 import decode_base64
@@ -31,7 +32,7 @@ from synapse.util.logcontext import (
)
from synapse.util.metrics import measure_func
from synapse.util.logutils import log_function
-from synapse.util.async import run_on_reactor
+from synapse.util.async import run_on_reactor, Linearizer
from synapse.util.frozenutils import unfreeze
from synapse.crypto.event_signing import (
compute_event_signature, add_hashes_and_signatures,
@@ -79,29 +80,216 @@ class FederationHandler(BaseHandler):
# When joining a room we need to queue any events for that room up
self.room_queues = {}
+ self._room_pdu_linearizer = Linearizer("fed_room_pdu")
- @log_function
@defer.inlineCallbacks
- def on_receive_pdu(self, origin, pdu, state=None, auth_chain=None):
- """ Called by the ReplicationLayer when we have a new pdu. We need to
- do auth checks and put it through the StateHandler.
+ @log_function
+ def on_receive_pdu(self, origin, pdu, get_missing=True):
+ """ Process a PDU received via a federation /send/ transaction, or
+ via backfill of missing prev_events
+
+ Args:
+ origin (str): server which initiated the /send/ transaction. Will
+ be used to fetch missing events or state.
+ pdu (FrozenEvent): received PDU
+ get_missing (bool): True if we should fetch missing prev_events
- auth_chain and state are None if we already have the necessary state
- and prev_events in the db
+ Returns (Deferred): completes with None
"""
- event = pdu
- logger.debug("Got event: %s", event.event_id)
+ # We reprocess pdus when we have seen them only as outliers
+ existing = yield self.get_persisted_pdu(
+ origin, pdu.event_id, do_auth=False
+ )
+
+ # FIXME: Currently we fetch an event again when we already have it
+ # if it has been marked as an outlier.
+
+ already_seen = (
+ existing and (
+ not existing.internal_metadata.is_outlier()
+ or pdu.internal_metadata.is_outlier()
+ )
+ )
+ if already_seen:
+ logger.debug("Already seen pdu %s", pdu.event_id)
+ return
# If we are currently in the process of joining this room, then we
# queue up events for later processing.
- if event.room_id in self.room_queues:
- self.room_queues[event.room_id].append((pdu, origin))
+ if pdu.room_id in self.room_queues:
+ logger.info("Ignoring PDU %s for room %s from %s for now; join "
+ "in progress", pdu.event_id, pdu.room_id, origin)
+ self.room_queues[pdu.room_id].append((pdu, origin))
return
- logger.debug("Processing event: %s", event.event_id)
+ state = None
+
+ auth_chain = []
+
+ have_seen = yield self.store.have_events(
+ [ev for ev, _ in pdu.prev_events]
+ )
+
+ fetch_state = False
+
+ # Get missing pdus if necessary.
+ if not pdu.internal_metadata.is_outlier():
+ # We only backfill backwards to the min depth.
+ min_depth = yield self.get_min_depth_for_context(
+ pdu.room_id
+ )
+
+ logger.debug(
+ "_handle_new_pdu min_depth for %s: %d",
+ pdu.room_id, min_depth
+ )
+
+ prevs = {e_id for e_id, _ in pdu.prev_events}
+ seen = set(have_seen.keys())
+
+ if min_depth and pdu.depth < min_depth:
+ # This is so that we don't notify the user about this
+ # message, to work around the fact that some events will
+ # reference really really old events we really don't want to
+ # send to the clients.
+ pdu.internal_metadata.outlier = True
+ elif min_depth and pdu.depth > min_depth:
+ if get_missing and prevs - seen:
+ # If we're missing stuff, ensure we only fetch stuff one
+ # at a time.
+ logger.info(
+ "Acquiring lock for room %r to fetch %d missing events: %r...",
+ pdu.room_id, len(prevs - seen), list(prevs - seen)[:5],
+ )
+ with (yield self._room_pdu_linearizer.queue(pdu.room_id)):
+ logger.info(
+ "Acquired lock for room %r to fetch %d missing events",
+ pdu.room_id, len(prevs - seen),
+ )
+
+ yield self._get_missing_events_for_pdu(
+ origin, pdu, prevs, min_depth
+ )
+
+ prevs = {e_id for e_id, _ in pdu.prev_events}
+ seen = set(have_seen.keys())
+ if prevs - seen:
+ logger.info(
+ "Still missing %d events for room %r: %r...",
+ len(prevs - seen), pdu.room_id, list(prevs - seen)[:5]
+ )
+ fetch_state = True
+
+ if fetch_state:
+ # We need to get the state at this event, since we haven't
+ # processed all the prev events.
+ logger.debug(
+ "_handle_new_pdu getting state for %s",
+ pdu.room_id
+ )
+ try:
+ state, auth_chain = yield self.replication_layer.get_state_for_room(
+ origin, pdu.room_id, pdu.event_id,
+ )
+ except:
+ logger.exception("Failed to get state for event: %s", pdu.event_id)
+
+ yield self._process_received_pdu(
+ origin,
+ pdu,
+ state=state,
+ auth_chain=auth_chain,
+ )
+
+ @defer.inlineCallbacks
+ def _get_missing_events_for_pdu(self, origin, pdu, prevs, min_depth):
+ """
+ Args:
+ origin (str): Origin of the pdu. Will be called to get the missing events
+ pdu: received pdu
+ prevs (str[]): List of event ids which we are missing
+ min_depth (int): Minimum depth of events to return.
+
+ Returns:
+ Deferred<dict(str, str?)>: updated have_seen dictionary
+ """
+ # We recalculate seen, since it may have changed.
+ have_seen = yield self.store.have_events(prevs)
+ seen = set(have_seen.keys())
- logger.debug("Event: %s", event)
+ if not prevs - seen:
+ # nothing left to do
+ defer.returnValue(have_seen)
+
+ latest = yield self.store.get_latest_event_ids_in_room(
+ pdu.room_id
+ )
+
+ # We add the prev events that we have seen to the latest
+ # list to ensure the remote server doesn't give them to us
+ latest = set(latest)
+ latest |= seen
+
+ logger.info(
+ "Missing %d events for room %r: %r...",
+ len(prevs - seen), pdu.room_id, list(prevs - seen)[:5]
+ )
+
+ # XXX: we set timeout to 10s to help workaround
+ # https://github.com/matrix-org/synapse/issues/1733.
+ # The reason is to avoid holding the linearizer lock
+ # whilst processing inbound /send transactions, causing
+ # FDs to stack up and block other inbound transactions
+ # which empirically can currently take up to 30 minutes.
+ #
+ # N.B. this explicitly disables retry attempts.
+ #
+ # N.B. this also increases our chances of falling back to
+ # fetching fresh state for the room if the missing event
+ # can't be found, which slightly reduces our security.
+ # it may also increase our DAG extremity count for the room,
+ # causing additional state resolution? See #1760.
+ # However, fetching state doesn't hold the linearizer lock
+ # apparently.
+ #
+ # see https://github.com/matrix-org/synapse/pull/1744
+
+ missing_events = yield self.replication_layer.get_missing_events(
+ origin,
+ pdu.room_id,
+ earliest_events_ids=list(latest),
+ latest_events=[pdu],
+ limit=10,
+ min_depth=min_depth,
+ timeout=10000,
+ )
+
+ # We want to sort these by depth so we process them and
+ # tell clients about them in order.
+ missing_events.sort(key=lambda x: x.depth)
+
+ for e in missing_events:
+ yield self.on_receive_pdu(
+ origin,
+ e,
+ get_missing=False
+ )
+
+ have_seen = yield self.store.have_events(
+ [ev for ev, _ in pdu.prev_events]
+ )
+ defer.returnValue(have_seen)
+
+ @log_function
+ @defer.inlineCallbacks
+ def _process_received_pdu(self, origin, pdu, state, auth_chain):
+ """ Called when we have a new pdu. We need to do auth checks and put it
+ through the StateHandler.
+ """
+ event = pdu
+
+ logger.debug("Processing event: %s", event)
# FIXME (erikj): Awful hack to make the case where we are not currently
# in the room work
@@ -670,8 +858,6 @@ class FederationHandler(BaseHandler):
"""
logger.debug("Joining %s to %s", joinee, room_id)
- yield self.store.clean_room_for_join(room_id)
-
origin, event = yield self._make_and_verify_event(
target_hosts,
room_id,
@@ -680,7 +866,15 @@ class FederationHandler(BaseHandler):
content,
)
+ # This shouldn't happen, because the RoomMemberHandler has a
+ # linearizer lock which only allows one operation per user per room
+ # at a time - so this is just paranoia.
+ assert (room_id not in self.room_queues)
+
self.room_queues[room_id] = []
+
+ yield self.store.clean_room_for_join(room_id)
+
handled_events = set()
try:
@@ -733,18 +927,37 @@ class FederationHandler(BaseHandler):
room_queue = self.room_queues[room_id]
del self.room_queues[room_id]
- for p, origin in room_queue:
- if p.event_id in handled_events:
- continue
+ # we don't need to wait for the queued events to be processed -
+ # it's just a best-effort thing at this point. We do want to do
+ # them roughly in order, though, otherwise we'll end up making
+ # lots of requests for missing prev_events which we do actually
+ # have. Hence we fire off the deferred, but don't wait for it.
- try:
- self.on_receive_pdu(origin, p)
- except:
- logger.exception("Couldn't handle pdu")
+ synapse.util.logcontext.preserve_fn(self._handle_queued_pdus)(
+ room_queue
+ )
defer.returnValue(True)
@defer.inlineCallbacks
+ def _handle_queued_pdus(self, room_queue):
+ """Process PDUs which got queued up while we were busy send_joining.
+
+ Args:
+ room_queue (list[FrozenEvent, str]): list of PDUs to be processed
+ and the servers that sent them
+ """
+ for p, origin in room_queue:
+ try:
+ logger.info("Processing queued PDU %s which was received "
+ "while we were joining %s", p.event_id, p.room_id)
+ yield self.on_receive_pdu(origin, p)
+ except Exception as e:
+ logger.warn(
+ "Error handling queued PDU %s from %s: %s",
+ p.event_id, origin, e)
+
+ @defer.inlineCallbacks
@log_function
def on_make_join_request(self, room_id, user_id):
""" We've received a /make_join/ request, so we create a partial
@@ -791,9 +1004,19 @@ class FederationHandler(BaseHandler):
)
event.internal_metadata.outlier = False
- # Send this event on behalf of the origin server since they may not
- # have an up to data view of the state of the room at this event so
- # will not know which servers to send the event to.
+ # Send this event on behalf of the origin server.
+ #
+ # The reasons we have the destination server rather than the origin
+ # server send it are slightly mysterious: the origin server should have
+ # all the neccessary state once it gets the response to the send_join,
+ # so it could send the event itself if it wanted to. It may be that
+ # doing it this way reduces failure modes, or avoids certain attacks
+ # where a new server selectively tells a subset of the federation that
+ # it has joined.
+ #
+ # The fact is that, as of the current writing, Synapse doesn't send out
+ # the join event over federation after joining, and changing it now
+ # would introduce the danger of backwards-compatibility problems.
event.internal_metadata.send_on_behalf_of = origin
context, event_stream_id, max_stream_id = yield self._handle_new_event(
@@ -878,15 +1101,15 @@ class FederationHandler(BaseHandler):
user_id,
"leave"
)
- signed_event = self._sign_event(event)
+ event = self._sign_event(event)
except SynapseError:
raise
except CodeMessageException as e:
logger.warn("Failed to reject invite: %s", e)
raise SynapseError(500, "Failed to reject invite")
- # Try the host we successfully got a response to /make_join/
- # request first.
+ # Try the host that we succesfully called /make_leave/ on first for
+ # the /send_leave/ request.
try:
target_hosts.remove(origin)
target_hosts.insert(0, origin)
@@ -896,7 +1119,7 @@ class FederationHandler(BaseHandler):
try:
yield self.replication_layer.send_leave(
target_hosts,
- signed_event
+ event
)
except SynapseError:
raise
@@ -1325,7 +1548,17 @@ class FederationHandler(BaseHandler):
@defer.inlineCallbacks
def _prep_event(self, origin, event, state=None, auth_events=None):
+ """
+
+ Args:
+ origin:
+ event:
+ state:
+ auth_events:
+ Returns:
+ Deferred, which resolves to synapse.events.snapshot.EventContext
+ """
context = yield self.state_handler.compute_event_context(
event, old_state=state,
)
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