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Pass back errors to the client when trying multiple federation destinations #9868

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merged 9 commits into from
Apr 27, 2021
Merged

Pass back errors to the client when trying multiple federation destinations #9868

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e782e86
Do not manually raise SynapseError.
clokep Apr 21, 2021
990f5df
Clarify comments.
clokep Apr 22, 2021
46bec7e
Callbacks should raise the original HttpResponseException.
clokep Apr 22, 2021
da0b210
Consolidate some checks for unknown endpoints.
clokep Apr 22, 2021
12402ef
Apply similar logic to _do_send_invite.
clokep Apr 22, 2021
ce1e53b
Newsfragment
clokep Apr 22, 2021
24d3351
Merge remote-tracking branch 'origin/develop' into clokep/federation-…
clokep Apr 23, 2021
2a1e59e
Generate the SynapseError inside of _is_unknown_endpoint.
clokep Apr 23, 2021
2450803
Update docstring with error conditions.
clokep Apr 23, 2021
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84 changes: 41 additions & 43 deletions synapse/federation/federation_client.py
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Original file line number Diff line number Diff line change
Expand Up @@ -451,6 +451,20 @@ async def get_event_auth(

return signed_auth

def _is_unknown_endpoint(
self, e: HttpResponseException, synapse_error: SynapseError
) -> bool:
"""
Returns true if the response was due to an endpoint being unimplemented.
"""
# There is no good way to detect an "unknown" endpoint.
#
# Dendrite returns a 404 (with no body); synapse returns a 400
# with M_UNRECOGNISED.
return e.code == 404 or (
e.code == 400 and synapse_error.errcode == Codes.UNRECOGNIZED
)

async def _try_destination_list(
self,
description: str,
Expand All @@ -468,9 +482,9 @@ async def _try_destination_list(
callback: Function to run for each server. Passed a single
argument: the server_name to try.

If the callback raises a CodeMessageException with a 300/400 code,
attempts to perform the operation stop immediately and the exception is
reraised.
If the callback raises a CodeMessageException with a 300/400 code or
an UnsupportedRoomVersionError, 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
Expand All @@ -492,8 +506,7 @@ async def _try_destination_list(
continue

try:
res = await callback(destination)
return res
return await callback(destination)
except InvalidResponseError as e:
logger.warning("Failed to %s via %s: %s", description, destination, e)
except UnsupportedRoomVersionError:
Expand All @@ -502,17 +515,15 @@ async def _try_destination_list(
synapse_error = e.to_synapse_error()
failover = False

# Failover on an internal server error, or if the destination
# doesn't implemented the endpoint for some reason.
if 500 <= e.code < 600:
failover = True

elif failover_on_unknown_endpoint:
# there is no good way to detect an "unknown" endpoint. Dendrite
# returns a 404 (with no body); synapse returns a 400
# with M_UNRECOGNISED.
if e.code == 404 or (
e.code == 400 and synapse_error.errcode == Codes.UNRECOGNIZED
):
failover = True
elif failover_on_unknown_endpoint and self._is_unknown_endpoint(
e, synapse_error
):
failover = True

if not failover:
raise synapse_error from e
Expand Down Expand Up @@ -570,9 +581,8 @@ async def make_membership_event(
UnsupportedRoomVersionError: if remote responds with
a room version we don't understand.

SynapseError: if the chosen remote server returns a 300/400 code.

RuntimeError: if no servers were reachable.
SynapseError: if the chosen remote server returns a 300/400 code, or
no servers successfully handle the request.
"""
valid_memberships = {Membership.JOIN, Membership.LEAVE}
if membership not in valid_memberships:
Expand Down Expand Up @@ -642,9 +652,8 @@ async def send_join(
``auth_chain``.

Raises:
SynapseError: if the chosen remote server returns a 300/400 code.

RuntimeError: if no servers were reachable.
SynapseError: if the chosen remote server returns a 300/400 code, or
no servers successfully handle the request.
"""

async def send_request(destination) -> Dict[str, Any]:
Expand Down Expand Up @@ -673,7 +682,7 @@ async def send_request(destination) -> Dict[str, Any]:
if create_event 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")
raise InvalidResponseError("No create event in state")

# the room version should be sane.
create_room_version = create_event.content.get(
Expand Down Expand Up @@ -746,16 +755,11 @@ async def _do_send_join(self, destination: str, pdu: EventBase) -> JsonDict:
content=pdu.get_pdu_json(time_now),
)
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, or an
# unrecognised endpoint error, we assume that the remote understands
# the v2 invite API and this is a legitimate error.
if err.errcode not in [Codes.UNKNOWN, Codes.UNRECOGNIZED]:
raise err
else:
raise e.to_synapse_error()
# If an error is received that is due to an unrecognised endpoint,
# fallback to the v1 endpoint. Otherwise consider it a legitmate error
# and raise.
if not self._is_unknown_endpoint(e, e.to_synapse_error()):
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raise

logger.debug("Couldn't send_join with the v2 API, falling back to the v1 API")

Expand Down Expand Up @@ -865,9 +869,8 @@ async def send_leave(self, destinations: Iterable[str], pdu: EventBase) -> None:
pdu: event to be sent

Raises:
SynapseError if the chosen remote server returns a 300/400 code.

RuntimeError if no servers were reachable.
SynapseError: if the chosen remote server returns a 300/400 code, or
no servers successfully handle the request.
"""

async def send_request(destination: str) -> None:
Expand All @@ -889,16 +892,11 @@ async def _do_send_leave(self, destination: str, pdu: EventBase) -> JsonDict:
content=pdu.get_pdu_json(time_now),
)
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, or an
# unrecognised endpoint error, we assume that the remote understands
# the v2 invite API and this is a legitimate error.
if err.errcode not in [Codes.UNKNOWN, Codes.UNRECOGNIZED]:
raise err
else:
raise e.to_synapse_error()
# If an error is received that is due to an unrecognised endpoint,
# fallback to the v1 endpoint. Otherwise consider it a legitmate error
# and raise.
if not self._is_unknown_endpoint(e, e.to_synapse_error()):
raise

logger.debug("Couldn't send_leave with the v2 API, falling back to the v1 API")

Expand Down