Hulahoop

A fast and efficient consistent hashing implementation, with support for virtual nodes.

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Usage

    use hulahoop::HashRing;

    let mut ring: HashRing<&str, _> = HashRing::default();

    // Nodes only need to implement Hash
    // Provide a weight to define the number of virtual nodes
    ring.insert("10.0.0.1:1234", 10);
    ring.insert("10.0.0.2:1234", 10);

    // Keys also only need to implement Hash
    assert_eq!(ring.get("Some key"), Some(&"10.0.0.1:1234"));
    assert_eq!(ring.get("Another key"), Some(&"10.0.0.2:1234"));

    ring.remove(&"10.0.0.2:1234");

    assert_eq!(ring.get("Some key"), Some(&"10.0.0.1:1234"));
    assert_eq!(ring.get("Another key"), Some(&"10.0.0.1:1234"));

HashRing uses Arc under the hood to allocate memory only per node and not for every virtual node added via the weight parameter.

The Hashring is Send + Sync.

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Hashers

Per default, hulahoop uses std::collections::hash_map::DefaultHasher to hash values.

Custom hashers can be used with the HashRing::with_hasher() method:

    use rustc_hash::FxHasher;
    let mut ring: HashRing<&str, _> = HashRing::with_hasher(BuildHasherDefault::<FxHasher>::default());

For convenience, the faster hasher FxHasher can be used by activating the fxhash feature of this crate.

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Benchmarks

	DefaultHasher	FxHasher (feature=fxhash)
Get (key length = 10)	13ns	8ns
Get (key length = 100)	31ns	12ns
Get (key length = 1000)	305ns	137ns
Add (weight = 1)	290ns	210ns
Add (weight = 10)	1.4us	1.0us
Add (weight = 100)	17.0us	14.3us

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License

This project is licensed optionally under either:

• Apache License, Version 2.0, (LICENSE-APACHE or https://www.apache.org/licenses/LICENSE-2.0)
• MIT license (LICENSE-MIT or https://opensource.org/licenses/MIT)