4 posts tagged with "kahuna"

Kahuna started as a simple idea: build a lightweight tool that centralizes the distributed concerns every team eventually runs into. Locks, leader election, configuration, sequences. Things that are easy to get wrong and painful to debug when they break at 3 a.m.

Somewhere along the way, it became something else entirely.

Today I am releasing Kahuna 1.0, and the system that ships is far more than the coordination library I set out to build. Kahuna is a distributed key/value database with transactions, a scripting engine, horizontal scalability, and enough correctness testing to bet real workloads on it.

Distributed systems usually look reliable when everything is healthy. The network is fast, every server is online, and requests arrive in a convenient order.

But what happens when a server loses contact with the rest of the cluster? What if a process stops while handling a request? What if Kahuna saves a value, but the reply never reaches the client?

We recently added a public Jepsen test suite for Kahuna to explore these difficult situations. It creates real Kahuna clusters, sends many requests at the same time, and introduces failures on purpose. It then checks whether Kahuna still keeps its promises.

Our goal is not only to see green test results. We want to find rare problems, understand them, and make sure they do not return.

Distributed transactions rarely fail in dramatic ways. They fail in boring ways.

A client writes key account:alice, the response gets lost, the client retries, another request starts commit, and now the system has to answer a simple question: did that write count?

That is the kind of question Kahuna should answer on the server, not push onto every client library and application.

The next step for Kahuna transactions is a reusable transaction coordinator: one server-owned place that tracks what a transaction has read, written, locked, retried, committed, or rolled back.

About eight years ago, I had the opportunity to build systems for my company using Erlang. Discovering the actor model was a turning point in how I designed systems from that moment on. However, for strategic reasons, we had to move away from Erlang and focus on the .NET ecosystem. While robust and well-established actor model libraries for C# exist, they included many features we didn’t need, and their performance wasn’t entirely satisfactory for our use cases. This led me to the idea of building a lightweight library.