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4f5d10ccd0
The futurization refactoring in9d3755f276("replica: Futurize retrieval of sstable sets in compaction_group_view") changed maybe_wait_for_sstable_count_reduction() from a single predicated wait: ``` co_await cstate.compaction_done.wait([..] { return num_runs_for_compaction() <= threshold || !can_perform_regular_compaction(t); }); ``` to a while loop with a predicated wait: ``` while (can_perform_regular_compaction(t) && co_await num_runs_for_compaction() > threshold) { co_await cstate.compaction_done.wait([this, &t] { return !can_perform_regular_compaction(t); }); } ``` This was necessary because num_runs_for_compaction() became a coroutine (returns future<size_t>) and can no longer be called inside a condition_variable predicate (which must be synchronous). However, the inner wait's predicate — !can_perform_regular_compaction(t) — only returns true when compaction is disabled or the table is being removed. During normal operation, every signal() from compaction_done wakes the waiter, the predicate returns false, and the waiter immediately goes back to sleep without ever re-checking the outer while loop's num_runs_for_compaction() condition. This causes memtable flushes to hang forever in maybe_wait_for_sstable_count_reduction() whenever the sstable run count exceeds the threshold, because completed compactions signal compaction_done but the signal is swallowed by the predicate. Fix by replacing the predicated wait with a bare wait(), so that any signal (including from completed compactions) causes the outer while loop to re-evaluate num_runs_for_compaction(). Fixes: https://scylladb.atlassian.net/browse/SCYLLADB-610 Closes scylladb/scylladb#28801 (cherry picked from commitbb57b0f3b7)