max.incremental.fetch.session.cache.slots — Kafka Broker Configuration
The maximum number of total incremental fetch sessions that we will maintain. FetchSessionCache is sharded into 8 shards and the limit is equally divided among all shards.
Description
The maximum number of total incremental fetch sessions that we will maintain. FetchSessionCache is sharded into 8 shards and the limit is equally divided among all shards. Sessions are allocated to each shard in round-robin. Only entries within a shard are considered eligible for eviction.
Default Values by Kafka Version
| Kafka Version | Default Value |
|---|---|
| 1.1 | 1000 |
| 2.0 | 1000 |
| 2.1 | 1000 |
| 2.2 | 1000 |
| 2.3 | 1000 |
| 2.4 | 1000 |
| 2.5 | 1000 |
| 2.6 | 1000 |
| 2.7 | 1000 |
| 2.8 | 1000 |
| 3.0 | 1000 |
| 3.1 | 1000 |
| 3.2 | 1000 |
| 3.3 | 1000 |
| 3.4 | 1000 |
| 3.5 | 1000 |
| 3.6 | 1000 |
| 3.7 | 1000 |
| 3.8 | 1000 |
| 3.9 | 1000 |
| 4.0 | 1000 |
| 4.1 | 1000 |
| 4.2 | 1000 |
Tuning Recommendation
| Profile | Recommended | Why |
|---|---|---|
| broker / throughput | 2000 | Incremental fetch sessions (KIP-227) let consumers send O(partition_changes) per FetchRequest instead of O(all_partitions). When cache is full (>1000 active consumers), sessions are evicted and consumers fall back to full enumeration — wasting network bandwidth. |
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