PERF: There seems to be a memory leakage in frontend-store

saquetim · 16 januari 2026 om 19:58

PERF: Prevent unbounded growth of store identity map

main ← perf/prevent-evergrowing-cache-store

merged 09:14PM - 19 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.

The PR above will address the memory leak reported in the OP.

Topic		Antwoorden	Weergaven
`decorateCooked` should be supplied with an `id` option to avoid memory leaks Support	5	881	14 juni 2019
Memory is running out and Discourse stops working Bug	74	14267	17 februari 2015
Leak of stylesheet_cache targets? Dev	0	417	24 april 2021
Performance improvements on long topics? Support	30	5484	20 augustus 2018
Memory use gradually ramps up after restart Installation server-resources	9	225	6 juli 2025

PERF: There seems to be a memory leakage in frontend-store

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