fix(lru-cache): include URL key length in getItemsLru size accounting#94942
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fix(lru-cache): include URL key length in getItemsLru size accounting#94942sleitor wants to merge 1 commit into
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The calculateSize callback in LRUCache only received the value, omitting the key (URL string). In the filesystem router, this meant that the URL key – which can be long in path-heavy apps – was never counted toward the cache's memory budget, causing under-eviction and excessive heap retention on long-lived servers. Changes: - Extend LRUCache.calculateSize signature to pass key as the second argument (backward-compatible: existing callbacks that ignore it continue to work unchanged). - Update getItemsLru in filesystem.ts to include key.length in the returned size for both positive and negative (null) cache entries. Fixes vercel#94890
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What?
The
calculateSizecallback inLRUCacheonly received the cached value, omitting the key (URL string). In the filesystem router, the URL key – which can be long in path-heavy apps – was never counted toward the cache's memory budget.Why?
This causes under-eviction: the LRU cache believes entries are smaller than they really are, so it evicts too infrequently, leading to excessive heap retention in long-lived servers handling many unique URLs.
How?
lru-cache.ts— Extend thecalculateSizecallback signature to passkeyas a second argument. This is fully backward-compatible: all existing callers that only usevaluecontinue to work unchanged (TypeScript allows functions with fewer parameters to satisfy a type requiring more).filesystem.ts— Update thegetItemsLrusize function to includekey.lengthfor both positive cache entries and negative (null) entries, so the full URL string is counted toward the cache budget.Fixes #94890