feat(event cache): automatically shrink a room's linked chunk when all subscribers are gone #4703
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…orage updates And rename it accordingly to `RoomEvents::store_updates`. Note: no changelog, because this is an internal API only.
…isteners are left
Codecov ReportAttention: Patch coverage is
Additional details and impacted files@@ Coverage Diff @@
## main #4703 +/- ##
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+ Coverage 85.89% 85.91% +0.02%
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Files 292 292
Lines 33907 33968 +61
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+ Hits 29124 29185 +61
Misses 4783 4783 ☔ View full report in Codecov by Sentry. |
Hywan
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Feb 21, 2025
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| // I hear you from the future: "but, spawning a detached task in a drop | ||
| // implementation is real bad! Maybe there will be multiple shrinks | ||
| // happening at the same time, and that's bad!". However, this can't | ||
| // happen, because the whole `state` variable is guarded by a fair lock, | ||
| // which will run queries in the order they happen. Should be fine™. |
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You forgot to explain why you need to spawn here. It's because drop cannot be async, and you're doing async operations.
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On top of #4694.
Every subscriber to a
RoomEventCachenow gets a shared reference to a RAIIAutoShrinkLinkedChunkguard; when the last one is dropped, it's spawning a task (from theDropimpl — sigh to no async drop) that will shrink the linked chunk to the last chunk.This is a poor man's implementation that doesn't cause too much operational overhead, in particular, because it doesn't require a new task listening to commands to shrink the linked chunk. (This new task should then live in the main
EventCacheinstance, so as not to have one such task perRoomEventCache, aka per room.)In the worst case, we can tweak the implementation and (mostly) keep the test, because it's testing the behavior we'd want here.
Part of #3280.