Initialise: don't snapshot without create event #266
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kegsay
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Aug 22, 2023
in case someone is playing silly buggers
DMRobertson
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Aug 22, 2023
These rooms have invalid state snapshots, leading to correctness problems. The existence of such snapshots leaves us open to performance problems due to gappy state updates. We have prevented invalid state snapshots from being formed (#255, #266) in the future. The remaining hole is to discard existing invalid snapshots. Closes #256.
DMRobertson
commented
Sep 7, 2023
| Str("room_id", roomID). | ||
| Int("len_state", len(events)). | ||
| Msg(errMsg) | ||
| return fmt.Errorf(errMsg) |
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This should have been a DataError. Otherwise the poller will end up retrying the same sync again and again.
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Followup to #255. Prerequisite for #256.
We don't want there to be "bogus" snapshots without a create event. We used to create such snapshots if we were informed of a stray state event in a room timeline. #235 targeted on known occurrance; #255 stopped this more generally.
We noticed another way to create bogus snapshots today. Namely: if the first time the proxy saw a room it had a state block lacking a create event. We don't think Synapse has been sending us these (outside of a gappy sync, where it is expected). But let's err towards caution to try and keep the database sane.