Kafka Error UNSUPPORTED_ASSIGNOR
Error code 112 · Non-retriable Consumer
The assignor or its version range is not supported by the consumer group.
Common Causes
- The consumer is configured with a custom or third-party partition assignor class that is not recognized by the broker-side group coordinator (KIP-848 server-side assignors differ from client-side ones).
- Version mismatch: the consumer specifies an assignor version range (min/max) that doesn't overlap with what the broker's group coordinator supports, typically because the broker version is older than what the assignor requires.
- Typo or incorrect fully-qualified class name in `partition.assignment.strategy` configuration, or the assignor JAR is missing from the classpath.
Solutions
- For the new consumer protocol (KIP-848), use only broker-supported server-side assignors. Check broker config `group.consumer.assignors` and, if needed, set the client-side `group.remote.assignor` to a supported built-in assignor such as `uniform` or `range`.
- If using a custom assignor, verify it implements the correct interface for the target Kafka version and that the version range declared in the assignor metadata is compatible with the broker. Upgrade the broker or downgrade the assignor version requirement.
- Fall back to the classic consumer group protocol by setting `group.protocol=classic` in consumer config if the custom assignor only supports classic rebalances, until the broker supports the new protocol.
Diagnostic Commands
# Check server-side partition assignors
kafka-configs.sh --bootstrap-server localhost:9092 --entity-type brokers --entity-default --describe | grep -E 'group.consumer.assignors|group.coordinator.rebalance.protocols'
# Describe consumer group offsets and lag
kafka-consumer-groups.sh --bootstrap-server localhost:9092 --describe --group <group-id> 2>&1 | head -30Related APIs
This error can be returned by: ConsumerGroupHeartbeat
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