README

Flexihash is a small PHP library which implements consistent hashing, which is most useful in distributed caching.

Note

This repo is a fork of https://github.com/pda/flexihash which had no release since 2020. Originally authored by @pda, @dmnc and @serima

Installation

Composer is the recommended installation technique. You can find flexihash on Packagist so installation is as easy as

composer require bcremer/flexihash

or in your composer.json

{
    "require": {
        "bcremer/flexihash": "^5.0.0"
    }
}

Usage

$hash = new Flexihash();

// bulk add
$hash->addTargets(['cache-1', 'cache-2', 'cache-3']);

// simple lookup
$hash->lookup('object-a'); // "cache-1"
$hash->lookup('object-b'); // "cache-2"

// add and remove
$hash->addTarget('cache-4');
$hash->removeTarget('cache-1');

// lookup with next-best fallback (for redundant writes)
$hash->lookupList('object', 2); // ["cache-2", "cache-4"]

// remove cache-2, expect object to hash to cache-4
$hash->removeTarget('cache-2');
$hash->lookup('object'); // "cache-4"

Benchmarks

Performance can be tested with PHPBench.

git checkout main
./vendor/bin/phpbench run --report=aggregate --iterations=4  --tag=branch_main

git checkout some-branch
./vendor/bin/phpbench run --report=aggregate --iterations=4  --ref=branch_main

Tests

Unit Test

composer test

Benchmark Test

vendor/bin/phpunit tests/BenchmarkTest.php

Further Reading

• http://www.spiteful.com/2008/03/17/programmers-toolbox-part-3-consistent-hashing/
• http://weblogs.java.net/blog/tomwhite/archive/2007/11/consistent_hash.html