ConsistentHashing

A .NET Standard 2.0 implementation of consistent hashing.

GitHub repo: https://github.com/jlao/ConsistentHashing

Getting Started

Install the NuGet package:

https://www.nuget.org/packages/ConsistentHashing/

Add a using statement:

using ConsistentHashing;

The primary class is HashRing<TNode> which implements IConsistentHashRing<TNode>. We'll start by creating a hash ring and adding a few nodes. We use string for our node class, but it can be anything that implements IComparable<TNode>.

var hashRing = new HashRing<string>();

hashRing.AddNode("a", 100);
hashRing.AddNode("b", 200);
hashRing.AddNode("a", 250);
hashRing.AddNode("c", 300);

This creates a consistent hash ring with the following ownership ranges:

• a: (200, 250], (300, 100]
• b: (100, 200]
• c: (250, 300]

Note that you can add the same node multiple times and it will own multiple ranges. Node a's second range, (300, 100] wraps around so it covers 301 to uint.MaxValue and 0 to 100.

Now we can do ownership checks:

Assert.Equal("a", hashRing.GetNode(0));
Assert.Equal("a", hashRing.GetNode(100));
Assert.Equal("a", hashRing.GetNode(500));
Assert.Equal("b", hashRing.GetNode(200));
Assert.Equal("a", hashRing.GetNode(225));
Assert.Equal("c", hashRing.GetNode(300));
Assert.Equal("a", hashRing.GetNode(400));

We can enumerate all the partitions:

foreach (Partition<string> p in hashRing.Partitions)
{
    Console.WriteLine($"{p.Node}: ({p.Range.StartExclusive}, {p.Range.EndInclusive}]");
}

Which will output:

b: (100, 200]
a: (200, 250]
c: (250, 300]
a: (300, 100]