#hash-map #memoization #cache #blocking


An ever-growing concurrent hash map with key-level locking granularity

2 releases

0.1.3 Mar 5, 2022
0.1.2 Mar 31, 2021
0.1.1 Jan 8, 2021
0.1.0 Dec 19, 2020

#164 in Caching


192 lines


The waitcache crate provides the type WaitCache<K, V>, an ever-growing concurrent hash map with key-level locking granularity. A hash map of this kind is useful for memoizing highly expensive functions, such as those requiring disk or network accesses. Unlike other cache implementations, WaitCache only ever resolves a value once, preventing expensive computations from duplicating work.


Inline rustdoc documentation is available. A mirror of this documentation is available at https://docs.rs/waitcache.


waitcache is developed at GitLab.

Reasonable performance, correctness, documentation, and ease-of-use contributions are always welcome. Bug reports and feature suggestions are accepted through GitLab.

Pull Requests

Please ensure pull requests match the existing coding style and are formatted with rustfmt.

Spelling and grammatical errors are considered bugs, so please use spell-checking facilities prior to submitting a contribution.

Contribution Agreement

By contributing, you grant all contributors a perpetual, worldwide, non-exclusive, no-charge, royalty-free, irrevocable copyright license to reproduce, prepare derivative works of, publicly display, publicly perform, relicense, sublicense, and distribute your contributions.

Additionally, you affirm that you are legally entitled to grant such license and that your contributions are not and will not become patent-encumbered. In the event that you discover that such affirmation was made in error, you agree to post notice of such error in a conspicuous place (such as a GitLab Issue) within three days.


waitcache is licensed under the terms of the Mozilla Public License, v. 2.0. All Source Code Forms are "Incompatible With Secondary Licenses", as described in §3.3 of the license.

The corresponding SPDX license identifier is MPL-2.0-no-copyleft-exception.


This document is Copyright (C) 2020 Nathan Sharp.

Permission is granted to reproduce this document, in any form, free of charge. The source code form of this document is subject to the terms of the Mozilla Public License, v. 2.0.


~20K SLoC