Deflake Join_should_succeed_when_joined_to_allowed_room subtest of restricted rooms tests

[DMRobertson]

This doesn't make it robust enough for Synapse to relax. There is another race whose details I would like to write down somewhere. Here will do.

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There is a race of some kind in Join_should_succeed_when_invited where:

• Alice invites Bob to a room
• Bob tries to join it, but is told he cannot because he isn't a member of the allowed_room. (Synapse doesn't seem to recognise Bob's invite.)

It smells a lot like matrix-org/synapse#13185 (though not exactly the same). I have traced it down to some kind of inconsistent view of the world within Synapse.

 event_creator1 | 2022-07-13 12:42:03,329 - synapse.access.http.18013 - 450 - INFO - POST-8 - ::ffff:127.0.0.1 - 18013 - {@alice:hs1} Processed request: 0.078sec/0.000sec (0.009sec, 0.000sec) (0.003sec/0.026sec/14) 2B 200 "POST /_matrix/client/r0/rooms/%21gKKiEPeUuvMlLRcsYn:hs1/invite HTTP/1.0" "Go-http-client/1.1" [0 dbevts]
  event_creator1 | 2022-07-13 12:42:03,331 - synapse.http.servlet - 663 - WARNING - POST-9 - Unable to parse JSON: Expecting value: line 1 col  umn 1 (char 0) (b'')
  event_creator1 | 2022-07-13 12:42:03,331 - synapse.handlers.room_member - 661 - WARNING - POST-9 - DMR: effective_membership_state='join'
  event_creator1 | 2022-07-13 12:42:03,331 - synapse.handlers.room_member - 725 - WARNING - POST-9 - DMR: prev_event_ids=None
  event_creator1 | 2022-07-13 12:42:03,332 - synapse.handlers.room_member - 745 - WARNING - POST-9 - DMR: latest_event_ids=['$9NYsPEfWiCn6tVyGwSHpsTV7_6ptI-MZ6dg0MY3OhpM']
  event_creator1 | 2022-07-13 12:42:03,336 - synapse.handlers.room_member - 755 - WARNING - POST-9 - DMR: old_state_id='$9NYsPEfWiCn6tVyGwSHpsTV7_6ptI-MZ6dg0MY3OhpM'
  event_creator1 | 2022-07-13 12:42:03,337 - synapse.handlers.room_member - 759 - WARNING - POST-9 - DMR: old_membership='invite'
  event_creator1 | 2022-07-13 12:42:03,337 - synapse.handlers.room_member - 808 - WARNING - POST-9 - DMR: is_host_in_room=True
  event_creator1 | 2022-07-13 12:42:03,339 - synapse.handlers.room_member - 1038 - WARNING - POST-9 - DMR: prev_member_event_id='$10lGB5PerDiK5mwdJMEC2HF0xWOkS4nmcei4AUb4vus'
  event_creator1 | 2022-07-13 12:42:03,339 - synapse.handlers.room_member - 1042 - WARNING - POST-9 - DMR: prev_member_event.membership='leave'
  event_creator1 | 2022-07-13 12:42:03,339 - synapse.handlers.event_auth - 189 - WARNING - POST-9 - DMR: prev_member_event=<FrozenEventV3 event_id=$10lGB5PerDiK5mwdJMEC2HF0xWOkS4nmcei4AUb4vus, type=m.room.member, state_key=@bob:hs1, outlier=False>
  event_creator1 | 2022-07-13 12:42:03,339 - synapse.handlers.event_auth - 191 - WARNING - POST-9 - DMR: prev_member_event.membership='leave'
  event_creator1 | 2022-07-13 12:42:03,339 - synapse.http.server - 167 - INFO - POST-9 - <SynapseRequest at 0x7f4bfdf56130 method='POST' uri='/_matrix/client/r0/join/%21gKKiEPeUuvMlLRcsYn:hs1?server_name=hs1' clientproto='HTTP/1.0' site='18013'> SynapseError: 403 - You do not belong to any of the required rooms/spaces to join this room.
  event_creator1 | 2022-07-13 12:42:03,339 - synapse.access.http.18013 - 450 - INFO - POST-9 - ::ffff:127.0.0.1 - 18013 - {@bob:hs1} Processed request: 0.008sec/0.000sec (0.002sec, 0.000sec) (0.001sec/0.002sec/6) 108B 403 "POST /_matrix/client/r0/join/%21gKKiEPeUuvMlLRcsYn:hs1?server_name=hs1 HTTP/1.0" "Go-http-client/1.1" [1 dbevts]

old_membership='invite' but prev_member_event.membership='leave'???

[squahtx]

LGTM!

I don't think the dendrite test failures are a regression. They're failing on dendrite's develop branch too and they're in an unrelated test anyway.

[neilalexander]

Dendrite failures are waiting for #411 to be resolved.