php-consistent-hashing

Multi-probe consistent hashing, using php

The idea behind this package is that you can distribute keys to nodes in a consistent/sticky way, while also allowing for custom weights for each node. This allows you to route 'traffic' to nodes using equal or unequal distributions.

The algorithm should distribute more evenly than for example libketama, which can have a deviation between distributions of equal weight as big as about 10%. For more information on this algorithm and consistent hashing in general, see:

• https://arxiv.org/abs/1505.00062
• https://en.wikipedia.org/wiki/Consistent_hashing

Use cases:

• Load balancing distributed caches.
• Data partitioning.
• Selecting a specific server and sticking with it (consistent routing).
• Distributing users over several groups. For use in A/B testing for example.

Example usage:

$hasher = new \Jspeedz\PhpConsistentHashing\MultiProbeConsistentHash();
// Choose which hash functions to use
$hasher->setHashFunctions((new \Jspeedz\PhpConsistentHashing\HashFunctions\Standard)());

Usage with equal weights:

$hasher->addNode('node1');
$hasher->addNode('node2');
$hasher->addNode('node2');

$node = $hasher->hash('some_key1');

Usage with custom weights (I like to use percentages):

$hasher->addNode('node1', 25);
$hasher->addNode('node2', 33.3);
$hasher->addNode('node2', 41.7);

$node = $hasher->hash('some_key1');

Note: if you add a node without specifying a weight, the weight will be set to 1.