Switch to WeakMap and String objects to avoid memory leak. Fixes #20 and #34. #43
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TimDaub
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Problem:
- Original code used `let sanitized = {}` which never garbage collects
- This causes unbounded memory growth in SSR scenarios
- Heap analysis showed ~5,400 concatenated strings per feed generation
Solution:
- Replace plain object with LRUCache from lru-cache package
- Cap at 10,000 entries (~2 feed generations worth)
- Count-based eviction with 5 MB safety cap
- Maintains string primitives (no String object overhead like WeakMap approach)
Based on heap analysis:
- ~21,500 strings/minute growth rate
- ~5,400 strings per feed (15s regeneration cycle)
- Average string size: ~32 bytes
- 10,000 entries = ~320 KB stable memory footprint
Related: developit#20, developit#34, developit#43
TimDaub
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- Replace LRU cache with WeakMap approach from PR developit#43 - Use String objects as WeakMap keys for automatic garbage collection - Memory bounded to active rendering context, no manual management needed - Update tests to use valueOf() to convert String objects to primitives Fixes developit#20, developit#34 Based on: developit#43
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This won't work because we're now returning strings |
TimDaub
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Oct 21, 2025
- Replace unbounded cache with WeakMap - Return String objects instead of primitives - String objects can be WeakMap keys and are GC'd automatically - No eviction issues - entries only released when truly unreferenced - Requires calling .valueOf() on final result before serialization This approach is based on PR developit#43 but adapted for server-side usage.
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Adding a new PR here to start the discussion on solving #20 again.
PR Switch to a WeakMap to avoid memory leak #23 aims to solve SSR Memory leak #20 by switching to WeakMap, but it uses string primitives as keys and will throw
TypeError: Invalid value used as weak map key.PR Switch sanitization to a Set and add cleanup #36 switches to a Set for storing the sanitized strings, but we risk evicting strings from the set before using them, changing the output of
vhtml()to escaped text.This PR switches to WeakMap (as in #23), but uses string objects as keys. This will have a performance impact, and change the output from
vhtml()from string primitives to string objects.The question is if it's worth taking the performance impact to solve both #20 and #34.