PERF: frontend-store にメモリリークがあるようです

saquetim · 2026 年 1 月 16 日午後 7:58

PERF: Prevent unbounded growth of store identity map

main ← perf/prevent-evergrowing-cache-store

approved 08:41AM - 16 Jan 26 UTC

Fixes a memory leak reported by @small-lovely-cat in https://meta.discourse.org/…t/perf-there-seems-to-be-a-memory-leakage-in-frontend-store/393510/1 ## Problem The store's identity map holds strong references to every model instance ever fetched during a session. These references are never released, causing memory to grow unbounded as users navigate through the application. Models for topics, posts, categories, and other resources accumulate indefinitely, even after the user has navigated away and the app no longer needs them. ## Why not FIFO/LRU? Traditional cache eviction strategies don't work well for an identity map. If we evict an entry while the app still holds a reference to that model (e.g., it's rendered in a component), the object remains in memory anyway. Worse, the next fetch for that ID creates a *new* instance—consuming more memory and breaking identity semantics where the same ID should always return the same object. ## Solution Introduce `WeakValueMap`, a Map that holds weak references to its values. When a model instance is no longer referenced anywhere else in the application, it becomes eligible for garbage collection, and the identity map entry is automatically cleaned up. **Key implementation details:** - `WeakRef` wraps cached values, allowing GC when unreferenced - `FinalizationRegistry` removes stale map entries after values are collected - Probabilistic sweep (~1% of `get()` calls) as a backup cleanup mechanism This makes the identity map self-regulating—it naturally shrinks when models are no longer in use, while still preserving identity semantics for active models.

上記のPRは、OPで報告されたメモリリークに対処します。

トピック		返信	表示
`decorateCooked` should be supplied with an `id` option to avoid memory leaks Support	4	910	2019 年 6 月 14 日
Memory is running out and Discourse stops working Bug	74	14553	2015 年 2 月 17 日
Leak of stylesheet_cache targets? Development	0	425	2021 年 4 月 24 日
Performance improvements on long topics? Support	29	5603	2018 年 7 月 12 日
Memory use gradually ramps up after restart Self-hosting server-resources	9	303	2025 年 7 月 6 日

PERF: frontend-store にメモリリークがあるようです

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