num.io.threads — Kafka Broker Configuration
The number of threads that the server uses for processing requests, which may include disk I/O.
Description
The number of threads that the server uses for processing requests, which may include disk I/O
Default Values by Kafka Version
| Kafka Version | Default Value |
|---|---|
| 0.8.0 | 8 |
| 0.8.1 | 8 |
| 0.8.2 | 8 |
| 0.9.0 | 8 |
| 0.10.0 | 8 |
| 0.10.1 | 8 |
| 0.10.2 | 8 |
| 0.11.0 | 8 |
| 1.0 | 8 |
| 1.1 | 8 |
| 2.0 | 8 |
| 2.1 | 8 |
| 2.2 | 8 |
| 2.3 | 8 |
| 2.4 | 8 |
| 2.5 | 8 |
| 2.6 | 8 |
| 2.7 | 8 |
| 2.8 | 8 |
| 3.0 | 8 |
| 3.1 | 8 |
| 3.2 | 8 |
| 3.3 | 8 |
| 3.4 | 8 |
| 3.5 | 8 |
| 3.6 | 8 |
| 3.7 | 8 |
| 3.8 | 8 |
| 3.9 | 8 |
| 4.0 | 8 |
| 4.1 | 8 |
| 4.2 | 8 |
Tuning Recommendation
| Profile | Recommended | Why |
|---|---|---|
| broker / throughput | 16 | IO threads perform the actual disk reads/writes for produce and fetch requests. When using HDDs or when the broker hosts many partitions, IO operations queue up; doubling to 16 keeps disk utilization high without stalling the network layer. |
| broker / latency | 16 | More I/O threads parallelize disk reads for fetch requests, reducing time spent waiting for disk I/O especially on spinning disks or under heavy consumer load. |
Related Configs
num.network.threads · queued.max.requests · num.recovery.threads.per.data.dir · compression.type · log.flush.interval.messages · log.flush.interval.ms
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