fix(sdk): Remove SlidingSyncInner::past_positions
#3833
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The patch matrix-org#2395 has introduced `SlidingSyncInner::past_positions` as a mechanism to filter duplicated responses. It was a problem because the sliding sync `ops` could easily create corrupted states if they were applied more than once. Since matrix-org#3664, `ops` are ignored. Now, `past_positions` create a problem with the sliding sync native implementation inside Synapse because `pos` can stay the same between multiple responses. While `past_positions` was helpful to fix bugs in the past, it's no longer necessary today. Moreover, it breaks an invariant about `pos`: we must consider it as a blackbox. It means we must ignore if a `pos` value has been received in the past or not. This invariant has been broken for good reasons, but it now creates new issues. This patch removes `past_positions`, along with the associated code (like `Error::ResponseAlreadyReceived` for example).
Hywan
requested review from
jmartinesp,
bnjbvr and
stefanceriu
and removed request for
a team and
jmartinesp
stefanceriu
approved these changes
Aug 12, 2024
Codecov ReportAll modified and coverable lines are covered by tests ✅
Additional details and impacted files@@ Coverage Diff @@
## main #3833 +/- ##
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- Coverage 84.12% 84.10% -0.02%
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Files 263 263
Lines 27592 27582 -10
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- Hits 23211 23199 -12
- Misses 4381 4383 +2 ☔ View full report in Codecov by Sentry. |
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The patch #2395 has introduced
SlidingSyncInner::past_positionsas a mechanism to filter duplicated responses. It was a problem because the sliding syncopscould easily create corrupted states if they were applied more than once.Since #3664,
opsare ignored.Now,
past_positionscreate a problem with the sliding sync native implementation inside Synapse becauseposcan stay the same between multiple responses.While
past_positionswas helpful to fix bugs in the past, it's no longer necessary today. Moreover, it breaks an invariant aboutpos: we must consider it as a blackbox. It means we must ignore if aposvalue has been received in the past or not. This invariant has been broken for good reasons, but it now creates new issues.This patch removes
past_positions, along with the associated code (likeError::ResponseAlreadyReceivedfor example).