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 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, build a cluster, and try taking a broker down.