synapse/changelog.d/11454.bugfix
Sean Quah 7ff22d6da4
Fix LruCache corruption bug with a size_callback that can return 0 (#11454)
When all entries in an `LruCache` have a size of 0 according to the
provided `size_callback`, and `drop_from_cache` is called on a cache
node, the node would be unlinked from the LRU linked list but remain in
the cache dictionary. An assertion would be later be tripped due to the
inconsistency.

Avoid unintentionally calling `__len__` and use a strict `is None`
check instead when unwrapping the weak reference.
2021-11-30 16:28:02 +00:00

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Fix an `LruCache` corruption bug, introduced in 1.38.0, that would cause certain requests to fail until the next Synapse restart.