flush() is durability work: it must cost what the current window's
deltas cost, never what the history backlog costs. Under adaptive
retention the byte budget derives from free memory, so bulk-load
pressure shrank the budget exactly at peak write volume and flush paid
actual reclaim inline — a production deployment measured single writes
blocked 25-191s behind reclaim-on-flush.
- flush() no longer calls autoCompactHistory(); close() is THE
auto-compaction site (already ran there; now alone).
- Every auto pass is time-bounded (CLOSE_COMPACTION_BUDGET_MS = 5s):
reclamation is oldest-first, so an early stop is a consistent prefix
and the next pass resumes. Explicit compactHistory() gains an
optional timeBudgetMs for caller-chosen maintenance windows.
- Documented trade stated where operators read: a long-lived writer
that never closes accumulates history until its next explicit
compactHistory() — predictable writes, explicit maintenance.
Pins: flush-never-reclaims + close-reclaims-durably (db-mvcc), bounded
pass stops-then-resumes as a consistent prefix (generationStore unit).
David Snelling
300d9f2a16