Kafka Error INELIGIBLE_REPLICA
Error code 107 · Non-retriable Broker
The new ISR contains at least one ineligible replica.
Common Causes
- An ISR expansion or AlterPartition request tried to add a replica to the ISR that has not yet caught up to the leader's high watermark
- A reassignment attempted to add a replica to the ISR that is currently under-replicated or lagging beyond replica.lag.time.max.ms
- Manual ISR manipulation (via AdminClient) included a replica that is offline or has a log end offset significantly behind the leader
Solutions
- Wait for the lagging replica to fully catch up before expecting it to join the ISR — monitor replica lag with kafka-topics.sh --under-replicated-partitions
- Increase replica.fetch.max.bytes or replica.socket.receive.buffer.bytes if replicas are consistently slow to catch up due to bandwidth constraints
- For stuck replicas, check the follower broker's disk I/O and network latency to the leader; resolve the bottleneck before the replica can become ISR-eligible
Diagnostic Commands
# Check for under-replicated partitions
kafka-topics.sh --bootstrap-server localhost:9092 --describe --under-replicated-partitions
# Describe topic replicas and ISR status
kafka-topics.sh --bootstrap-server localhost:9092 --describe --topic <topic-name> | grep -E 'Isr|Replicas'Related APIs
This error can be returned by: AlterPartition
Debugging Kafka errors? Conduktor Console gives you real-time visibility into your cluster. Explore all errors in the Error Decoder.