---
title: "Kafka Simulator v1.7 - chaos and the Failure Lab"
date: 2026-09-18T00:00:00.000Z
author: "michal"
excerpt: "Kill brokers, split the network, and watch your cluster recover. v1.7 adds the Failure Lab to free play, six chaos scenarios, and a more usable mobile playground."
---
v1.7 adds six chaos scenarios and brings the Failure Lab to free play. You can now build a cluster, take brokers down, split the network, and follow what happens as it recovers.

The [Kafka Simulator](/kafka-simulator/) curriculum now covers 80 of 122 scenarios.

## The Failure Lab

Until now, failures were part of scripted scenarios. You could follow a broker going down, but you couldn't pick a different broker or try the same failure in your own topology.

The Failure Lab gives you those controls in free play:

- **Kill and restart brokers.** Watch what happens to leaders and replicas when a broker disappears, then bring it back.
- **Create network partitions.** Split the cluster and follow which partitions retain a leader, which go leaderless, and how the ISR changes.
- **Watch recovery.** Heal the network or restart a broker, then step through the cluster as it recovers.

The six new scenarios walk through failures with a known outcome. In free play, you choose the topology and the faults.

That leaves room for questions the scenarios don't cover. What if a different broker went down? What if you lost a second one before the first had caught up? You can try these without setting up a real cluster or cleaning up afterwards.

The Failure Lab also records your actions. Faults, produce operations, and configuration changes appear in the same log used by `?actions=` links, so you can see what a shared link will replay.

## A more usable playground on mobile

The playground already opened on a phone. Using it was another matter: labels were too small, controls crowded the diagram, and opening the details panel made it hard to keep track of the cluster.

This release reworks that layout:

- **Larger labels and less wasted space.** The diagram follows its content more closely, and brokers that are down collapse to a header showing their offline status.
- **A draggable details panel.** Keep the current step visible at the bottom, pull the panel up to read alongside the cluster, or expand it fully.
- **Smaller controls.** The toolbar, playback speed, and timeline take up less room.

We also fixed labels being clipped at the edge of some multi-DC diagrams. Those were disappearing entirely, not just becoming hard to read.

## Finding a scenario

The scenario library now supports search by ID or title, difficulty filters with counts, and filters by scenario length. These are available on desktop too.

Open the [simulator](/kafka-simulator/), build a cluster, and try taking a broker down.