Kafka Error BROKER_NOT_AVAILABLE
Error code 8 · Non-retriable Broker
The broker is not available.
Common Causes
- Broker process is down or still starting and has not yet registered with the controller / cluster metadata
- Broker is recovering logs or shutting down, so it is not yet ready to serve requests even though the port may be open
- Clients are using a stale or wrong endpoint from advertised.listeners and are trying to reach a broker address that is not actually usable
Solutions
- Check the broker process and its startup log first. If it crashed, fix the fatal error before restarting; if it is still recovering logs, wait for registration to complete
- Verify listeners on that node: listeners, advertised.listeners, and listener.security.protocol.map must advertise an address that clients can actually reach
- If the cluster is short on brokers, treat this as a broker availability problem, not a client tuning problem: bring the missing broker back or reassign partitions off it; only lower min.insync.replicas as a temporary incident action if you accept the durability trade-off
Diagnostic Commands
# Check broker supported API versions
kafka-broker-api-versions.sh --bootstrap-server <broker>:9092
# Look for startup, registration, or fatal errors in broker logs
grep -E 'ERROR|FATAL|BrokerRegistration|started|BrokerNotAvailable' /var/log/kafka/server.log | tail -30
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