Introduction

Dynamically modifies the broker's num.io.threads configuration to reduce the number of threads available for disk I/O operations. This can cause increased latency or request timeouts under load. The original value is automatically restored when the attack ends.

Details

Kafka restricts large changes to its current configuration. If the requested number of I/O threads falls outside the permissible range, the extension applies intermediate adjustments incrementally until the target value is achieved.

Use Cases

• Reduce I/O threads to simulate degraded disk performance and test how producers/consumers handle increased latency.
• Verify that client timeout and retry settings are appropriate when broker I/O capacity is limited.

Parameters

Parameter	Description	Default
Duration	How long the configuration change stays in effect. The original num.io.threads value is automatically restored when the duration expires.	60s
Number of IO Threads	The target number of I/O threads per broker. Set to a low value (e.g., 1) to severely limit disk I/O capacity. The original value is restored at the end of the attack. The change may be applied incrementally if Kafka's permissible range requires it.