MatrixSynapse/synapse/federation/federation_client.py

995 lines
35 KiB
Python

# -*- coding: utf-8 -*-
# Copyright 2015, 2016 OpenMarket 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 copy
import itertools
import logging
from six.moves import range
from prometheus_client import Counter
from twisted.internet import defer
from synapse.api.constants import EventTypes, Membership
from synapse.api.errors import (
CodeMessageException,
Codes,
FederationDeniedError,
HttpResponseException,
SynapseError,
)
from synapse.api.room_versions import (
KNOWN_ROOM_VERSIONS,
EventFormatVersions,
RoomVersions,
)
from synapse.events import builder, room_version_to_event_format
from synapse.federation.federation_base import FederationBase, event_from_pdu_json
from synapse.logging.context import make_deferred_yieldable, run_in_background
from synapse.logging.utils import log_function
from synapse.util import unwrapFirstError
from synapse.util.caches.expiringcache import ExpiringCache
from synapse.util.retryutils import NotRetryingDestination
logger = logging.getLogger(__name__)
sent_queries_counter = Counter("synapse_federation_client_sent_queries", "", ["type"])
PDU_RETRY_TIME_MS = 1 * 60 * 1000
class InvalidResponseError(RuntimeError):
"""Helper for _try_destination_list: indicates that the server returned a response
we couldn't parse
"""
pass
class FederationClient(FederationBase):
def __init__(self, hs):
super(FederationClient, self).__init__(hs)
self.pdu_destination_tried = {}
self._clock.looping_call(self._clear_tried_cache, 60 * 1000)
self.state = hs.get_state_handler()
self.transport_layer = hs.get_federation_transport_client()
self.hostname = hs.hostname
self.signing_key = hs.config.signing_key[0]
self._get_pdu_cache = ExpiringCache(
cache_name="get_pdu_cache",
clock=self._clock,
max_len=1000,
expiry_ms=120 * 1000,
reset_expiry_on_get=False,
)
def _clear_tried_cache(self):
"""Clear pdu_destination_tried cache"""
now = self._clock.time_msec()
old_dict = self.pdu_destination_tried
self.pdu_destination_tried = {}
for event_id, destination_dict in old_dict.items():
destination_dict = {
dest: time
for dest, time in destination_dict.items()
if time + PDU_RETRY_TIME_MS > now
}
if destination_dict:
self.pdu_destination_tried[event_id] = destination_dict
@log_function
def make_query(
self,
destination,
query_type,
args,
retry_on_dns_fail=False,
ignore_backoff=False,
):
"""Sends a federation Query to a remote homeserver of the given type
and arguments.
Args:
destination (str): Domain name of the remote homeserver
query_type (str): Category of the query type; should match the
handler name used in register_query_handler().
args (dict): Mapping of strings to strings containing the details
of the query request.
ignore_backoff (bool): true to ignore the historical backoff data
and try the request anyway.
Returns:
a Deferred which will eventually yield a JSON object from the
response
"""
sent_queries_counter.labels(query_type).inc()
return self.transport_layer.make_query(
destination,
query_type,
args,
retry_on_dns_fail=retry_on_dns_fail,
ignore_backoff=ignore_backoff,
)
@log_function
def query_client_keys(self, destination, content, timeout):
"""Query device keys for a device hosted on a remote server.
Args:
destination (str): Domain name of the remote homeserver
content (dict): The query content.
Returns:
a Deferred which will eventually yield a JSON object from the
response
"""
sent_queries_counter.labels("client_device_keys").inc()
return self.transport_layer.query_client_keys(destination, content, timeout)
@log_function
def query_user_devices(self, destination, user_id, timeout=30000):
"""Query the device keys for a list of user ids hosted on a remote
server.
"""
sent_queries_counter.labels("user_devices").inc()
return self.transport_layer.query_user_devices(destination, user_id, timeout)
@log_function
def claim_client_keys(self, destination, content, timeout):
"""Claims one-time keys for a device hosted on a remote server.
Args:
destination (str): Domain name of the remote homeserver
content (dict): The query content.
Returns:
a Deferred which will eventually yield a JSON object from the
response
"""
sent_queries_counter.labels("client_one_time_keys").inc()
return self.transport_layer.claim_client_keys(destination, content, timeout)
@defer.inlineCallbacks
@log_function
def backfill(self, dest, room_id, limit, extremities):
"""Requests some more historic PDUs for the given context from the
given destination server.
Args:
dest (str): The remote home server to ask.
room_id (str): The room_id to backfill.
limit (int): The maximum number of PDUs to return.
extremities (list): List of PDU id and origins of the first pdus
we have seen from the context
Returns:
Deferred: Results in the received PDUs.
"""
logger.debug("backfill extrem=%s", extremities)
# If there are no extremeties then we've (probably) reached the start.
if not extremities:
return
transaction_data = yield self.transport_layer.backfill(
dest, room_id, extremities, limit
)
logger.debug("backfill transaction_data=%r", transaction_data)
room_version = yield self.store.get_room_version(room_id)
format_ver = room_version_to_event_format(room_version)
pdus = [
event_from_pdu_json(p, format_ver, outlier=False)
for p in transaction_data["pdus"]
]
# FIXME: We should handle signature failures more gracefully.
pdus[:] = yield make_deferred_yieldable(
defer.gatherResults(
self._check_sigs_and_hashes(room_version, pdus), consumeErrors=True
).addErrback(unwrapFirstError)
)
return pdus
@defer.inlineCallbacks
@log_function
def get_pdu(
self, destinations, event_id, room_version, outlier=False, timeout=None
):
"""Requests the PDU with given origin and ID from the remote home
servers.
Will attempt to get the PDU from each destination in the list until
one succeeds.
Args:
destinations (list): Which home servers to query
event_id (str): event to fetch
room_version (str): version of the room
outlier (bool): Indicates whether the PDU is an `outlier`, i.e. if
it's from an arbitary point in the context as opposed to part
of the current block of PDUs. Defaults to `False`
timeout (int): How long to try (in ms) each destination for before
moving to the next destination. None indicates no timeout.
Returns:
Deferred: Results in the requested PDU, or None if we were unable to find
it.
"""
# TODO: Rate limit the number of times we try and get the same event.
ev = self._get_pdu_cache.get(event_id)
if ev:
return ev
pdu_attempts = self.pdu_destination_tried.setdefault(event_id, {})
format_ver = room_version_to_event_format(room_version)
signed_pdu = None
for destination in destinations:
now = self._clock.time_msec()
last_attempt = pdu_attempts.get(destination, 0)
if last_attempt + PDU_RETRY_TIME_MS > now:
continue
try:
transaction_data = yield self.transport_layer.get_event(
destination, event_id, timeout=timeout
)
logger.debug(
"retrieved event id %s from %s: %r",
event_id,
destination,
transaction_data,
)
pdu_list = [
event_from_pdu_json(p, format_ver, outlier=outlier)
for p in transaction_data["pdus"]
]
if pdu_list and pdu_list[0]:
pdu = pdu_list[0]
# Check signatures are correct.
signed_pdu = yield self._check_sigs_and_hash(room_version, pdu)
break
pdu_attempts[destination] = now
except SynapseError as e:
logger.info(
"Failed to get PDU %s from %s because %s", event_id, destination, e
)
continue
except NotRetryingDestination as e:
logger.info(str(e))
continue
except FederationDeniedError as e:
logger.info(str(e))
continue
except Exception as e:
pdu_attempts[destination] = now
logger.info(
"Failed to get PDU %s from %s because %s", event_id, destination, e
)
continue
if signed_pdu:
self._get_pdu_cache[event_id] = signed_pdu
return signed_pdu
@defer.inlineCallbacks
@log_function
def get_state_for_room(self, destination, room_id, event_id):
"""Requests all of the room state at a given event from a remote home server.
Args:
destination (str): The remote homeserver to query for the state.
room_id (str): The id of the room we're interested in.
event_id (str): The id of the event we want the state at.
Returns:
Deferred[Tuple[List[EventBase], List[EventBase]]]:
A list of events in the state, and a list of events in the auth chain
for the given event.
"""
try:
# First we try and ask for just the IDs, as thats far quicker if
# we have most of the state and auth_chain already.
# However, this may 404 if the other side has an old synapse.
result = yield self.transport_layer.get_room_state_ids(
destination, room_id, event_id=event_id
)
state_event_ids = result["pdu_ids"]
auth_event_ids = result.get("auth_chain_ids", [])
fetched_events, failed_to_fetch = yield self.get_events_from_store_or_dest(
destination, room_id, set(state_event_ids + auth_event_ids)
)
if failed_to_fetch:
logger.warning(
"Failed to fetch missing state/auth events for %s: %s",
room_id,
failed_to_fetch,
)
event_map = {ev.event_id: ev for ev in fetched_events}
pdus = [event_map[e_id] for e_id in state_event_ids if e_id in event_map]
auth_chain = [
event_map[e_id] for e_id in auth_event_ids if e_id in event_map
]
auth_chain.sort(key=lambda e: e.depth)
return pdus, auth_chain
except HttpResponseException as e:
if e.code == 400 or e.code == 404:
logger.info("Failed to use get_room_state_ids API, falling back")
else:
raise e
result = yield self.transport_layer.get_room_state(
destination, room_id, event_id=event_id
)
room_version = yield self.store.get_room_version(room_id)
format_ver = room_version_to_event_format(room_version)
pdus = [
event_from_pdu_json(p, format_ver, outlier=True) for p in result["pdus"]
]
auth_chain = [
event_from_pdu_json(p, format_ver, outlier=True)
for p in result.get("auth_chain", [])
]
seen_events = yield self.store.get_events(
[ev.event_id for ev in itertools.chain(pdus, auth_chain)]
)
signed_pdus = yield self._check_sigs_and_hash_and_fetch(
destination,
[p for p in pdus if p.event_id not in seen_events],
outlier=True,
room_version=room_version,
)
signed_pdus.extend(
seen_events[p.event_id] for p in pdus if p.event_id in seen_events
)
signed_auth = yield self._check_sigs_and_hash_and_fetch(
destination,
[p for p in auth_chain if p.event_id not in seen_events],
outlier=True,
room_version=room_version,
)
signed_auth.extend(
seen_events[p.event_id] for p in auth_chain if p.event_id in seen_events
)
signed_auth.sort(key=lambda e: e.depth)
return signed_pdus, signed_auth
@defer.inlineCallbacks
def get_events_from_store_or_dest(self, destination, room_id, event_ids):
"""Fetch events from a remote destination, checking if we already have them.
Args:
destination (str)
room_id (str)
event_ids (list)
Returns:
Deferred: A deferred resolving to a 2-tuple where the first is a list of
events and the second is a list of event ids that we failed to fetch.
"""
seen_events = yield self.store.get_events(event_ids, allow_rejected=True)
signed_events = list(seen_events.values())
failed_to_fetch = set()
missing_events = set(event_ids)
for k in seen_events:
missing_events.discard(k)
if not missing_events:
return signed_events, failed_to_fetch
logger.debug(
"Fetching unknown state/auth events %s for room %s",
missing_events,
event_ids,
)
room_version = yield self.store.get_room_version(room_id)
batch_size = 20
missing_events = list(missing_events)
for i in range(0, len(missing_events), batch_size):
batch = set(missing_events[i : i + batch_size])
deferreds = [
run_in_background(
self.get_pdu,
destinations=[destination],
event_id=e_id,
room_version=room_version,
)
for e_id in batch
]
res = yield make_deferred_yieldable(
defer.DeferredList(deferreds, consumeErrors=True)
)
for success, result in res:
if success and result:
signed_events.append(result)
batch.discard(result.event_id)
# We removed all events we successfully fetched from `batch`
failed_to_fetch.update(batch)
return signed_events, failed_to_fetch
@defer.inlineCallbacks
@log_function
def get_event_auth(self, destination, room_id, event_id):
res = yield self.transport_layer.get_event_auth(destination, room_id, event_id)
room_version = yield self.store.get_room_version(room_id)
format_ver = room_version_to_event_format(room_version)
auth_chain = [
event_from_pdu_json(p, format_ver, outlier=True) for p in res["auth_chain"]
]
signed_auth = yield self._check_sigs_and_hash_and_fetch(
destination, auth_chain, outlier=True, room_version=room_version
)
signed_auth.sort(key=lambda e: e.depth)
return signed_auth
@defer.inlineCallbacks
def _try_destination_list(self, description, destinations, callback):
"""Try an operation on a series of servers, until it succeeds
Args:
description (unicode): description of the operation we're doing, for logging
destinations (Iterable[unicode]): list of server_names to try
callback (callable): Function to run for each server. Passed a single
argument: the server_name to try. May return a deferred.
If the callback raises a CodeMessageException with a 300/400 code,
attempts to perform the operation stop immediately and the exception is
reraised.
Otherwise, if the callback raises an Exception the error is logged and the
next server tried. Normally the stacktrace is logged but this is
suppressed if the exception is an InvalidResponseError.
Returns:
The [Deferred] result of callback, if it succeeds
Raises:
SynapseError if the chosen remote server returns a 300/400 code, or
no servers were reachable.
"""
for destination in destinations:
if destination == self.server_name:
continue
try:
res = yield callback(destination)
return res
except InvalidResponseError as e:
logger.warning("Failed to %s via %s: %s", description, destination, e)
except HttpResponseException as e:
if not 500 <= e.code < 600:
raise e.to_synapse_error()
else:
logger.warning(
"Failed to %s via %s: %i %s",
description,
destination,
e.code,
e.args[0],
)
except Exception:
logger.warning(
"Failed to %s via %s", description, destination, exc_info=1
)
raise SynapseError(502, "Failed to %s via any server" % (description,))
def make_membership_event(
self, destinations, room_id, user_id, membership, content, params
):
"""
Creates an m.room.member event, with context, without participating in the room.
Does so by asking one of the already participating servers to create an
event with proper context.
Returns a fully signed and hashed event.
Note that this does not append any events to any graphs.
Args:
destinations (Iterable[str]): Candidate homeservers which are probably
participating in the room.
room_id (str): The room in which the event will happen.
user_id (str): The user whose membership is being evented.
membership (str): The "membership" property of the event. Must be
one of "join" or "leave".
content (dict): Any additional data to put into the content field
of the event.
params (dict[str, str|Iterable[str]]): Query parameters to include in the
request.
Return:
Deferred[tuple[str, FrozenEvent, int]]: resolves to a tuple of
`(origin, event, event_format)` where origin is the remote
homeserver which generated the event, and event_format is one of
`synapse.api.room_versions.EventFormatVersions`.
Fails with a ``SynapseError`` if the chosen remote server
returns a 300/400 code.
Fails with a ``RuntimeError`` if no servers were reachable.
"""
valid_memberships = {Membership.JOIN, Membership.LEAVE}
if membership not in valid_memberships:
raise RuntimeError(
"make_membership_event called with membership='%s', must be one of %s"
% (membership, ",".join(valid_memberships))
)
@defer.inlineCallbacks
def send_request(destination):
ret = yield self.transport_layer.make_membership_event(
destination, room_id, user_id, membership, params
)
# Note: If not supplied, the room version may be either v1 or v2,
# however either way the event format version will be v1.
room_version = ret.get("room_version", RoomVersions.V1.identifier)
event_format = room_version_to_event_format(room_version)
pdu_dict = ret.get("event", None)
if not isinstance(pdu_dict, dict):
raise InvalidResponseError("Bad 'event' field in response")
logger.debug("Got response to make_%s: %s", membership, pdu_dict)
pdu_dict["content"].update(content)
# The protoevent received over the JSON wire may not have all
# the required fields. Lets just gloss over that because
# there's some we never care about
if "prev_state" not in pdu_dict:
pdu_dict["prev_state"] = []
ev = builder.create_local_event_from_event_dict(
self._clock,
self.hostname,
self.signing_key,
format_version=event_format,
event_dict=pdu_dict,
)
return (destination, ev, event_format)
return self._try_destination_list(
"make_" + membership, destinations, send_request
)
def send_join(self, destinations, pdu, event_format_version):
"""Sends a join event to one of a list of homeservers.
Doing so will cause the remote server to add the event to the graph,
and send the event out to the rest of the federation.
Args:
destinations (str): Candidate homeservers which are probably
participating in the room.
pdu (BaseEvent): event to be sent
event_format_version (int): The event format version
Return:
Deferred: resolves to a dict with members ``origin`` (a string
giving the serer the event was sent to, ``state`` (?) and
``auth_chain``.
Fails with a ``SynapseError`` if the chosen remote server
returns a 300/400 code.
Fails with a ``RuntimeError`` if no servers were reachable.
"""
def check_authchain_validity(signed_auth_chain):
for e in signed_auth_chain:
if e.type == EventTypes.Create:
create_event = e
break
else:
raise InvalidResponseError("no %s in auth chain" % (EventTypes.Create,))
# the room version should be sane.
room_version = create_event.content.get("room_version", "1")
if room_version not in KNOWN_ROOM_VERSIONS:
# This shouldn't be possible, because the remote server should have
# rejected the join attempt during make_join.
raise InvalidResponseError(
"room appears to have unsupported version %s" % (room_version,)
)
@defer.inlineCallbacks
def send_request(destination):
time_now = self._clock.time_msec()
_, content = yield self.transport_layer.send_join(
destination=destination,
room_id=pdu.room_id,
event_id=pdu.event_id,
content=pdu.get_pdu_json(time_now),
)
logger.debug("Got content: %s", content)
state = [
event_from_pdu_json(p, event_format_version, outlier=True)
for p in content.get("state", [])
]
auth_chain = [
event_from_pdu_json(p, event_format_version, outlier=True)
for p in content.get("auth_chain", [])
]
pdus = {p.event_id: p for p in itertools.chain(state, auth_chain)}
room_version = None
for e in state:
if (e.type, e.state_key) == (EventTypes.Create, ""):
room_version = e.content.get(
"room_version", RoomVersions.V1.identifier
)
break
if room_version is None:
# If the state doesn't have a create event then the room is
# invalid, and it would fail auth checks anyway.
raise SynapseError(400, "No create event in state")
valid_pdus = yield self._check_sigs_and_hash_and_fetch(
destination,
list(pdus.values()),
outlier=True,
room_version=room_version,
)
valid_pdus_map = {p.event_id: p for p in valid_pdus}
# NB: We *need* to copy to ensure that we don't have multiple
# references being passed on, as that causes... issues.
signed_state = [
copy.copy(valid_pdus_map[p.event_id])
for p in state
if p.event_id in valid_pdus_map
]
signed_auth = [
valid_pdus_map[p.event_id]
for p in auth_chain
if p.event_id in valid_pdus_map
]
# NB: We *need* to copy to ensure that we don't have multiple
# references being passed on, as that causes... issues.
for s in signed_state:
s.internal_metadata = copy.deepcopy(s.internal_metadata)
check_authchain_validity(signed_auth)
return {
"state": signed_state,
"auth_chain": signed_auth,
"origin": destination,
}
return self._try_destination_list("send_join", destinations, send_request)
@defer.inlineCallbacks
def send_invite(self, destination, room_id, event_id, pdu):
room_version = yield self.store.get_room_version(room_id)
content = yield self._do_send_invite(destination, pdu, room_version)
pdu_dict = content["event"]
logger.debug("Got response to send_invite: %s", pdu_dict)
room_version = yield self.store.get_room_version(room_id)
format_ver = room_version_to_event_format(room_version)
pdu = event_from_pdu_json(pdu_dict, format_ver)
# Check signatures are correct.
pdu = yield self._check_sigs_and_hash(room_version, pdu)
# FIXME: We should handle signature failures more gracefully.
return pdu
@defer.inlineCallbacks
def _do_send_invite(self, destination, pdu, room_version):
"""Actually sends the invite, first trying v2 API and falling back to
v1 API if necessary.
Args:
destination (str): Target server
pdu (FrozenEvent)
room_version (str)
Returns:
dict: The event as a dict as returned by the remote server
"""
time_now = self._clock.time_msec()
try:
content = yield self.transport_layer.send_invite_v2(
destination=destination,
room_id=pdu.room_id,
event_id=pdu.event_id,
content={
"event": pdu.get_pdu_json(time_now),
"room_version": room_version,
"invite_room_state": pdu.unsigned.get("invite_room_state", []),
},
)
return content
except HttpResponseException as e:
if e.code in [400, 404]:
err = e.to_synapse_error()
# If we receive an error response that isn't a generic error, we
# assume that the remote understands the v2 invite API and this
# is a legitimate error.
if err.errcode != Codes.UNKNOWN:
raise err
# Otherwise, we assume that the remote server doesn't understand
# the v2 invite API. That's ok provided the room uses old-style event
# IDs.
v = KNOWN_ROOM_VERSIONS.get(room_version)
if v.event_format != EventFormatVersions.V1:
raise SynapseError(
400,
"User's homeserver does not support this room version",
Codes.UNSUPPORTED_ROOM_VERSION,
)
elif e.code == 403:
raise e.to_synapse_error()
else:
raise
# Didn't work, try v1 API.
# Note the v1 API returns a tuple of `(200, content)`
_, content = yield self.transport_layer.send_invite_v1(
destination=destination,
room_id=pdu.room_id,
event_id=pdu.event_id,
content=pdu.get_pdu_json(time_now),
)
return content
def send_leave(self, destinations, pdu):
"""Sends a leave event to one of a list of homeservers.
Doing so will cause the remote server to add the event to the graph,
and send the event out to the rest of the federation.
This is mostly useful to reject received invites.
Args:
destinations (str): Candidate homeservers which are probably
participating in the room.
pdu (BaseEvent): event to be sent
Return:
Deferred: resolves to None.
Fails with a ``SynapseError`` if the chosen remote server
returns a 300/400 code.
Fails with a ``RuntimeError`` if no servers were reachable.
"""
@defer.inlineCallbacks
def send_request(destination):
time_now = self._clock.time_msec()
_, content = yield self.transport_layer.send_leave(
destination=destination,
room_id=pdu.room_id,
event_id=pdu.event_id,
content=pdu.get_pdu_json(time_now),
)
logger.debug("Got content: %s", content)
return None
return self._try_destination_list("send_leave", destinations, send_request)
def get_public_rooms(
self,
destination,
limit=None,
since_token=None,
search_filter=None,
include_all_networks=False,
third_party_instance_id=None,
):
if destination == self.server_name:
return
return self.transport_layer.get_public_rooms(
destination,
limit,
since_token,
search_filter,
include_all_networks=include_all_networks,
third_party_instance_id=third_party_instance_id,
)
@defer.inlineCallbacks
def get_missing_events(
self,
destination,
room_id,
earliest_events_ids,
latest_events,
limit,
min_depth,
timeout,
):
"""Tries to fetch events we are missing. This is called when we receive
an event without having received all of its ancestors.
Args:
destination (str)
room_id (str)
earliest_events_ids (list): List of event ids. Effectively the
events we expected to receive, but haven't. `get_missing_events`
should only return events that didn't happen before these.
latest_events (list): List of events we have received that we don't
have all previous events for.
limit (int): Maximum number of events to return.
min_depth (int): Minimum depth of events tor return.
timeout (int): Max time to wait in ms
"""
try:
content = yield self.transport_layer.get_missing_events(
destination=destination,
room_id=room_id,
earliest_events=earliest_events_ids,
latest_events=[e.event_id for e in latest_events],
limit=limit,
min_depth=min_depth,
timeout=timeout,
)
room_version = yield self.store.get_room_version(room_id)
format_ver = room_version_to_event_format(room_version)
events = [
event_from_pdu_json(e, format_ver) for e in content.get("events", [])
]
signed_events = yield self._check_sigs_and_hash_and_fetch(
destination, events, outlier=False, room_version=room_version
)
except HttpResponseException as e:
if not e.code == 400:
raise
# We are probably hitting an old server that doesn't support
# get_missing_events
signed_events = []
return signed_events
@defer.inlineCallbacks
def forward_third_party_invite(self, destinations, room_id, event_dict):
for destination in destinations:
if destination == self.server_name:
continue
try:
yield self.transport_layer.exchange_third_party_invite(
destination=destination, room_id=room_id, event_dict=event_dict
)
return None
except CodeMessageException:
raise
except Exception as e:
logger.exception(
"Failed to send_third_party_invite via %s: %s", destination, str(e)
)
raise RuntimeError("Failed to send to any server.")
@defer.inlineCallbacks
def get_room_complexity(self, destination, room_id):
"""
Fetch the complexity of a remote room from another server.
Args:
destination (str): The remote server
room_id (str): The room ID to ask about.
Returns:
Deferred[dict] or Deferred[None]: Dict contains the complexity
metric versions, while None means we could not fetch the complexity.
"""
try:
complexity = yield self.transport_layer.get_room_complexity(
destination=destination, room_id=room_id
)
defer.returnValue(complexity)
except CodeMessageException as e:
# We didn't manage to get it -- probably a 404. We are okay if other
# servers don't give it to us.
logger.debug(
"Failed to fetch room complexity via %s for %s, got a %d",
destination,
room_id,
e.code,
)
except Exception:
logger.exception(
"Failed to fetch room complexity via %s for %s", destination, room_id
)
# If we don't manage to find it, return None. It's not an error if a
# server doesn't give it to us.
defer.returnValue(None)