├── .gitignore ├── .travis.yml ├── Cargo.toml ├── LICENSE ├── README.md ├── build.rs └── src ├── conshash.rs ├── lib.rs └── maglev.rs /.gitignore: -------------------------------------------------------------------------------- 1 | # Generated by Cargo 2 | # will have compiled files and executables 3 | /target/ 4 | 5 | # Remove Cargo.lock from gitignore if creating an executable, leave it for libraries 6 | # More information here http://doc.crates.io/guide.html#cargotoml-vs-cargolock 7 | Cargo.lock 8 | .idea -------------------------------------------------------------------------------- /.travis.yml: -------------------------------------------------------------------------------- 1 | sudo: false 2 | language: rust 3 | rust: 4 | - stable 5 | - beta 6 | - nightly 7 | os: 8 | - osx 9 | - linux 10 | matrix: 11 | allow_failures: 12 | - rust: nightly 13 | env: 14 | global: 15 | - RUST_BACKTRACE=1 16 | script: 17 | - cargo build --verbose $FEATURES 18 | - cargo test --verbose $FEATURES 19 | cache: 20 | cargo: true 21 | directories: 22 | - $HOME/.cargo -------------------------------------------------------------------------------- /Cargo.toml: -------------------------------------------------------------------------------- 1 | [package] 2 | authors = ["Flier Lu "] 3 | description = "Maglev - Google's consistent hashing algorithm" 4 | documentation = "https://docs.rs/maglev" 5 | edition = "2018" 6 | homepage = "https://github.com/flier/rust-maglev" 7 | keywords = ["google", "maglev", "consistent", "hashing"] 8 | license = "Apache-2.0" 9 | name = "maglev" 10 | repository = "https://github.com/flier/rust-maglev.git" 11 | version = "0.2.1" 12 | 13 | [dependencies] 14 | primal = "0.3" 15 | 16 | [dev-dependencies] 17 | fasthash = "0.4" 18 | skeptic = "0.13" 19 | 20 | [build-dependencies] 21 | skeptic = "0.13" 22 | -------------------------------------------------------------------------------- /LICENSE: -------------------------------------------------------------------------------- 1 | Apache License 2 | Version 2.0, January 2004 3 | http://www.apache.org/licenses/ 4 | 5 | TERMS AND CONDITIONS FOR USE, REPRODUCTION, AND DISTRIBUTION 6 | 7 | 1. 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We also recommend that a 185 | file or class name and description of purpose be included on the 186 | same "printed page" as the copyright notice for easier 187 | identification within third-party archives. 188 | 189 | Copyright {yyyy} {name of copyright owner} 190 | 191 | Licensed under the Apache License, Version 2.0 (the "License"); 192 | you may not use this file except in compliance with the License. 193 | You may obtain a copy of the License at 194 | 195 | http://www.apache.org/licenses/LICENSE-2.0 196 | 197 | Unless required by applicable law or agreed to in writing, software 198 | distributed under the License is distributed on an "AS IS" BASIS, 199 | WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 200 | See the License for the specific language governing permissions and 201 | limitations under the License. 202 | -------------------------------------------------------------------------------- /README.md: -------------------------------------------------------------------------------- 1 | # rust-maglev [![travis build](https://api.travis-ci.org/flier/rust-maglev.svg)](https://travis-ci.org/flier/rust-maglev) [![crate](https://img.shields.io/crates/v/maglev.svg)](https://crates.io/crates/maglev) [![docs](https://docs.rs/maglev/badge.svg)](https://docs.rs/maglev/) 2 | Google's consistent hashing algorithm 3 | 4 | ## Usage 5 | 6 | To use `maglev`, first add this to your `Cargo.toml`: 7 | 8 | ```toml 9 | [dependencies] 10 | maglev = "0.2" 11 | ``` 12 | 13 | And then, use `Maglev` with `ConsistentHasher` trait 14 | 15 | ```rust 16 | use maglev::{ConsistentHasher, Maglev}; 17 | 18 | fn main() { 19 | let m = Maglev::new(vec!["Monday", 20 | "Tuesday", 21 | "Wednesday", 22 | "Thursday", 23 | "Friday", 24 | "Saturday", 25 | "Sunday"]); 26 | 27 | assert_eq!(m["alice"], "Friday"); 28 | assert_eq!(m["bob"], "Wednesday"); 29 | 30 | // When the node list changed, ensure to use same `capacity` to rebuild 31 | 32 | let m = Maglev::with_capacity(vec!["Monday", 33 | // "Tuesday", 34 | "Wednesday", 35 | // "Thursday", 36 | "Friday", 37 | "Saturday", 38 | "Sunday"], 39 | m.capacity()); 40 | 41 | assert_eq!(m["alice"], "Friday"); 42 | assert_eq!(m["bob"], "Wednesday"); 43 | } 44 | ``` 45 | 46 | Maglev use `std::collections::hash_map::DefaultHasher` by default, we could use the given hash builder to hash keys. 47 | 48 | ```rust 49 | use fasthash::spooky::Hash128; 50 | use maglev::Maglev; 51 | 52 | fn main() { 53 | let m = Maglev::with_hasher(vec!["Monday", 54 | "Tuesday", 55 | "Wednesday", 56 | "Thursday", 57 | "Friday", 58 | "Saturday", 59 | "Sunday"], 60 | Hash128 {}); 61 | 62 | assert_eq!(m["alice"], "Monday"); 63 | assert_eq!(m["bob"], "Wednesday"); 64 | } 65 | ``` -------------------------------------------------------------------------------- /build.rs: -------------------------------------------------------------------------------- 1 | fn main() { 2 | skeptic::generate_doc_tests(&["README.md"]); 3 | } 4 | -------------------------------------------------------------------------------- /src/conshash.rs: -------------------------------------------------------------------------------- 1 | use std::hash::Hash; 2 | 3 | /// Consistent hasher is a special kind of hashing such that when a hash table is resized, 4 | /// only `K/n` keys need to be remapped on average, where `K` is the number of keys, 5 | /// and `n` is the number of slots. 6 | pub trait ConsistentHasher { 7 | /// Returns all nodes in arbitrary order. 8 | fn nodes(&self) -> &[N]; 9 | 10 | /// Returns the number of slots in the lookup table. 11 | fn capacity(&self) -> usize; 12 | 13 | /// Returns a reference to the node corresponding to the key. 14 | fn get(&self, key: &Q) -> Option<&N> 15 | where 16 | Q: Hash + Eq; 17 | } 18 | -------------------------------------------------------------------------------- /src/lib.rs: -------------------------------------------------------------------------------- 1 | //! Maglev hashing - A consistent hashing algorithm from Google 2 | //! 3 | //! [Maglev: A Fast and Reliable Software Network Load Balancer](https://static.googleusercontent.com/media/research.google.com/zh-CN//pubs/archive/44824.pdf) 4 | //! 5 | //! # Example 6 | //! 7 | //! ```rust 8 | //! use maglev::*; 9 | //! 10 | //! let m = Maglev::new(vec!["Monday", 11 | //! "Tuesday", 12 | //! "Wednesday", 13 | //! "Thursday", 14 | //! "Friday", 15 | //! "Saturday", 16 | //! "Sunday"]); 17 | //! 18 | //! assert_eq!(m["alice"], "Friday"); 19 | //! assert_eq!(m["bob"], "Wednesday"); 20 | //! 21 | //! // When the node list changed, ensure to use same `capacity` to rebuild the lookup table. 22 | //! 23 | //! let m = Maglev::with_capacity(vec!["Monday", 24 | //! // "Tuesday", 25 | //! "Wednesday", 26 | //! // "Thursday", 27 | //! "Friday", 28 | //! "Saturday", 29 | //! "Sunday"], 30 | //! m.capacity()); 31 | //! 32 | //! assert_eq!(m["alice"], "Friday"); 33 | //! assert_eq!(m["bob"], "Wednesday"); 34 | //! ``` 35 | //! 36 | //! Maglev use `std::collections::hash_map::DefaultHasher` by default, 37 | //! we could use the given hash builder to hash keys. 38 | //! 39 | //! ```rust 40 | //! extern crate fasthash; 41 | //! extern crate maglev; 42 | //! 43 | //! use fasthash::spooky::Hash128; 44 | //! 45 | //! use maglev::*; 46 | //! 47 | //! fn main() { 48 | //! let m = Maglev::with_hasher(vec!["Monday", 49 | //! "Tuesday", 50 | //! "Wednesday", 51 | //! "Thursday", 52 | //! "Friday", 53 | //! "Saturday", 54 | //! "Sunday"], 55 | //! Hash128 {}); 56 | //! 57 | //! assert_eq!(m["alice"], "Monday"); 58 | //! assert_eq!(m["bob"], "Wednesday"); 59 | //! } 60 | //! ``` 61 | mod conshash; 62 | mod maglev; 63 | 64 | pub use crate::conshash::ConsistentHasher; 65 | pub use crate::maglev::Maglev; 66 | -------------------------------------------------------------------------------- /src/maglev.rs: -------------------------------------------------------------------------------- 1 | use std::collections::hash_map::DefaultHasher; 2 | use std::hash::{BuildHasher, BuildHasherDefault, Hash, Hasher}; 3 | use std::iter; 4 | use std::ops::Index; 5 | 6 | use primal::Sieve; 7 | 8 | use crate::conshash::ConsistentHasher; 9 | 10 | /// Maglev lookup table 11 | #[derive(Clone, Debug)] 12 | pub struct Maglev> { 13 | nodes: Vec, 14 | lookup: Option>, 15 | hash_builder: S, 16 | } 17 | 18 | impl Maglev> { 19 | /// Creates a `Maglev` lookup table. 20 | pub fn new>(nodes: I) -> Self { 21 | Maglev::with_capacity_and_hasher(nodes, 0, Default::default()) 22 | } 23 | 24 | /// Creates a `Maglev` lookup table with the specified capacity. 25 | pub fn with_capacity>(nodes: I, capacity: usize) -> Self { 26 | Maglev::with_capacity_and_hasher(nodes, capacity, Default::default()) 27 | } 28 | } 29 | 30 | impl Maglev { 31 | /// Creates a `Maglev` lookup table which will use the given hash builder to hash keys. 32 | pub fn with_hasher>(nodes: I, hash_builder: S) -> Self { 33 | Maglev::with_capacity_and_hasher(nodes, 0, hash_builder) 34 | } 35 | 36 | /// Creates a `Maglev` lookup table with the specified capacity, using hasher to hash the keys. 37 | pub fn with_capacity_and_hasher>( 38 | nodes: I, 39 | capacity: usize, 40 | hash_builder: S, 41 | ) -> Self { 42 | let nodes = nodes.into_iter().collect::>(); 43 | let lookup = Self::populate(&nodes, capacity, &hash_builder); 44 | 45 | Maglev { 46 | nodes, 47 | lookup, 48 | hash_builder, 49 | } 50 | } 51 | 52 | #[inline] 53 | fn hash_with_seed(key: &Q, seed: u32, hash_builder: &S) -> usize { 54 | let mut hasher = hash_builder.build_hasher(); 55 | hasher.write_u32(seed); 56 | key.hash(&mut hasher); 57 | hasher.finish() as usize 58 | } 59 | 60 | fn populate(nodes: &[N], mut capacity: usize, hash_builder: &S) -> Option> { 61 | if nodes.is_empty() { 62 | return None; 63 | } 64 | if capacity == 0 { 65 | capacity = nodes.len() * 100 66 | } 67 | let m = Sieve::new(capacity * 2) 68 | .primes_from(capacity) 69 | .next() 70 | .unwrap(); 71 | let n = nodes.len(); 72 | 73 | let permutation: Vec> = nodes 74 | .iter() 75 | .map(|node| { 76 | let offset = Self::hash_with_seed(&node, 0xdead_babe, &hash_builder) % m; 77 | let skip = (Self::hash_with_seed(&node, 0xdead_beef, &hash_builder) % (m - 1)) + 1; 78 | 79 | (0..m).map(|i| (offset + i * skip) % m).collect() 80 | }) 81 | .collect(); 82 | 83 | let mut next: Vec = vec![0; n]; 84 | let mut entry: Vec = vec![-1; m]; 85 | 86 | let mut j = 0; 87 | 88 | while j < m { 89 | for i in 0..n { 90 | let mut c = permutation[i][next[i]]; 91 | 92 | while entry[c] >= 0 { 93 | next[i] += 1; 94 | c = permutation[i][next[i]]; 95 | } 96 | 97 | entry[c] = i as isize; 98 | next[i] += 1; 99 | j += 1; 100 | 101 | if j == m { 102 | break; 103 | } 104 | } 105 | } 106 | 107 | Some(entry) 108 | } 109 | } 110 | 111 | impl iter::FromIterator for Maglev> { 112 | fn from_iter>(iter: T) -> Self { 113 | Maglev::new(iter) 114 | } 115 | } 116 | 117 | impl ConsistentHasher for Maglev 118 | where 119 | N: Hash + Eq, 120 | S: BuildHasher, 121 | { 122 | #[inline] 123 | fn nodes(&self) -> &[N] { 124 | self.nodes.as_slice() 125 | } 126 | 127 | #[inline] 128 | fn capacity(&self) -> usize { 129 | self.lookup.as_ref().map(|m| m.len()).unwrap_or_default() 130 | } 131 | 132 | #[inline] 133 | fn get(&self, key: &Q) -> Option<&N> 134 | where 135 | Q: Hash + Eq, 136 | { 137 | self.lookup.as_ref().map(|lookup| { 138 | let key = Self::hash_with_seed(key, 0xdead_babe, &self.hash_builder); 139 | 140 | &self.nodes[lookup[key % lookup.len()] as usize] 141 | }) 142 | } 143 | } 144 | 145 | impl Index<&Q> for Maglev 146 | where 147 | N: Hash + Eq, 148 | S: BuildHasher, 149 | Q: Hash + Eq + ?Sized, 150 | { 151 | type Output = N; 152 | 153 | fn index(&self, index: &Q) -> &Self::Output { 154 | self.get(index).unwrap() 155 | } 156 | } 157 | 158 | #[cfg(test)] 159 | pub mod tests { 160 | use fasthash::spooky::Hash128; 161 | 162 | use super::*; 163 | use crate::conshash::ConsistentHasher; 164 | 165 | include!(concat!(env!("OUT_DIR"), "/skeptic-tests.rs")); 166 | 167 | #[test] 168 | fn test_maglev() { 169 | let m = Maglev::new(vec![ 170 | "Monday", 171 | "Tuesday", 172 | "Wednesday", 173 | "Thursday", 174 | "Friday", 175 | "Saturday", 176 | "Sunday", 177 | ]); 178 | 179 | assert_eq!(m.nodes.len(), 7); 180 | assert_eq!(m.lookup.as_ref().unwrap().len(), 701); 181 | assert!(m 182 | .lookup 183 | .as_ref() 184 | .unwrap() 185 | .iter() 186 | .all(|&n| n < m.nodes.len() as isize)); 187 | 188 | assert_eq!(m["alice"], "Friday"); 189 | assert_eq!(m["bob"], "Wednesday"); 190 | 191 | let m = Maglev::with_capacity( 192 | vec![ 193 | "Monday", 194 | "Tuesday", 195 | "Wednesday", 196 | // "Thursday", 197 | "Friday", 198 | "Saturday", 199 | "Sunday", 200 | ], 201 | m.capacity(), 202 | ); 203 | 204 | assert_eq!(m.nodes.len(), 6); 205 | assert_eq!(m.lookup.as_ref().unwrap().len(), 701); 206 | assert!(m 207 | .lookup 208 | .as_ref() 209 | .unwrap() 210 | .iter() 211 | .all(|&n| n < m.nodes.len() as isize)); 212 | 213 | assert_eq!(m["alice"], "Friday"); 214 | assert_eq!(m["bob"], "Wednesday"); 215 | 216 | let m = Maglev::with_capacity( 217 | vec![ 218 | "Monday", 219 | // "Tuesday", 220 | "Wednesday", 221 | // "Thursday", 222 | "Friday", 223 | "Saturday", 224 | "Sunday", 225 | ], 226 | m.capacity(), 227 | ); 228 | 229 | assert_eq!(m.nodes.len(), 5); 230 | assert_eq!(m.lookup.as_ref().unwrap().len(), 701); 231 | assert!(m 232 | .lookup 233 | .as_ref() 234 | .unwrap() 235 | .iter() 236 | .all(|&n| n < m.nodes.len() as isize)); 237 | 238 | assert_eq!(m["alice"], "Friday"); 239 | assert_eq!(m["bob"], "Wednesday"); 240 | 241 | let m = Maglev::with_capacity( 242 | vec![ 243 | "Monday", 244 | "Tuesday", 245 | "Wednesday", 246 | // "Thursday", 247 | // "Friday", 248 | "Saturday", 249 | "Sunday", 250 | ], 251 | m.capacity(), 252 | ); 253 | 254 | assert_eq!(m.nodes.len(), 5); 255 | assert_eq!(m.lookup.as_ref().unwrap().len(), 701); 256 | assert!(m 257 | .lookup 258 | .as_ref() 259 | .unwrap() 260 | .iter() 261 | .all(|&n| n < m.nodes.len() as isize)); 262 | 263 | assert_eq!(m["alice"], "Saturday"); 264 | assert_eq!(m["bob"], "Wednesday"); 265 | } 266 | 267 | #[test] 268 | fn test_maglev_with_custom_hasher() { 269 | let m = Maglev::with_hasher( 270 | vec![ 271 | "Monday", 272 | "Tuesday", 273 | "Wednesday", 274 | "Thursday", 275 | "Friday", 276 | "Saturday", 277 | "Sunday", 278 | ], 279 | Hash128 {}, 280 | ); 281 | 282 | assert_eq!(m.nodes.len(), 7); 283 | assert_eq!(m.lookup.as_ref().unwrap().len(), 701); 284 | assert!(m 285 | .lookup 286 | .as_ref() 287 | .unwrap() 288 | .iter() 289 | .all(|&n| n < m.nodes.len() as isize)); 290 | 291 | assert_eq!(m["alice"], "Monday"); 292 | assert_eq!(m["bob"], "Wednesday"); 293 | 294 | let m = Maglev::with_capacity_and_hasher( 295 | vec![ 296 | "Monday", "Tuesday", // "Wednesday", 297 | "Thursday", // "Friday", 298 | "Saturday", "Sunday", 299 | ], 300 | m.capacity(), 301 | Hash128 {}, 302 | ); 303 | 304 | assert_eq!(m.nodes.len(), 5); 305 | assert_eq!(m.lookup.as_ref().unwrap().len(), 701); 306 | assert!(m 307 | .lookup 308 | .as_ref() 309 | .unwrap() 310 | .iter() 311 | .all(|&n| n < m.nodes.len() as isize)); 312 | 313 | assert_eq!(m["alice"], "Monday"); 314 | assert_eq!(m["bob"], "Sunday"); 315 | } 316 | 317 | #[test] 318 | fn test_maglev_with_empty_list() { 319 | let m = Maglev::<&str, _>::new(None); 320 | 321 | assert_eq!(m.nodes.len(), 0); 322 | assert!(m.lookup.is_none()); 323 | 324 | assert_eq!(m.get("alice"), None); 325 | } 326 | } 327 | --------------------------------------------------------------------------------