perf(segcache): reduce catalog write amplification with dirty flag - #408
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Add an atomic dirty flag to SegmentCache so SaveCatalog() is a no-op when nothing has changed. Also throttle LastAccess updates in Get() to at most once per 60 seconds, preventing read-only traffic from perpetually marking the catalog dirty. Increase the catalog flush ticker from 10s to 60s. Together these changes eliminate the ~720 MB/hr of bookkeeping writes that occurred unconditionally on a 10 GB cache (1-2 MB catalog.json every 10s), reducing SSD wear to near-zero during idle periods. Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
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Jun 1, 2026
…ipsilabs#408) Co-authored-by: Claude Sonnet 4.6 <noreply@anthropic.com>
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Summary
atomic.Booldirty flag toSegmentCache;SaveCatalog()is now a no-op when the catalog hasn't changed since the last flushLastAccessupdates inGet()to at most once per 60 seconds — read-only traffic no longer marks the catalog dirtycatalogFlushLoopticker from 10 s → 60 sMotivation
On a 10 GB cache (~13 000 entries) the
catalog.jsonis 1–2 MB. Writing it unconditionally every 10 s produced ~720 MB/hr of pure bookkeeping writes with zero data benefit — significant SSD wear during both idle and read-heavy periods.Test plan
go test ./internal/nzbfilesystem/segcache/...— all 12 tests passTestCacheSaveCatalogAndReloadconfirms dirty flag is set afterPut()and catalog round-trips correctlyGet()calls within 60 s should not triggerSaveCatalog()writes (dirty stays false)Put()followed by >60 s idle should result in one catalog write, then no-ops on subsequent ticks🤖 Generated with Claude Code