Kafka Error PRINCIPAL_DESERIALIZATION_FAILURE
Error code 97 · Non-retriable Security
Request principal deserialization failed during forwarding. This indicates an internal error on the broker cluster security setup.
Common Causes
- A forwarded request arrived at a broker with a principal serialized in a format the receiving broker cannot deserialize — typically due to a custom PrincipalBuilder mismatch across broker versions
- Mixed-version cluster during rolling upgrade where one broker uses a new principal serialization format not understood by older brokers receiving forwarded requests
- Custom security plugin or PrincipalBuilder implementation is not installed on all brokers, so forwarded requests with custom principals fail on brokers missing the plugin
Solutions
- Ensure all brokers have the same custom security plugins and PrincipalBuilder implementation deployed before enabling request forwarding
- During rolling upgrades, upgrade all brokers to the same version before sending requests that involve cross-broker forwarding with complex principal types
- Check broker logs for the deserialization exception class to identify which PrincipalBuilder or serialization format is mismatched
Diagnostic Commands
# Look for authorization failures in logs
grep 'PrincipalDeserializationFailure\|deserializ.*principal\|KafkaPrincipal' /var/log/kafka/server.log | tail -20
# Verify broker connectivity and API versions
kafka-broker-api-versions.sh --bootstrap-server localhost:9092 | head -5
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