kafka connection_error ai_generated true

org.apache.kafka.common.KafkaException: Failed to construct kafka consumer: Connection to node -1 (localhost/127.0.0.1:9092) could not be established. Broker may not be available.

ID: kafka/connection-refused-bootstrap

Also available as: JSON · Markdown
90%Fix Rate
90%Confidence
3Evidence
2023-01-01First Seen

Version Compatibility

VersionStatusIntroducedDeprecatedNotes
3 active — — —

Root Cause

Cannot connect to Kafka bootstrap server. Broker not running, wrong address, firewall blocking, or advertised.listeners misconfigured.

generic

Workarounds

  1. 92% success Verify broker is running and listening on expected port 
    ss -tlnp | grep 9092; sudo journalctl -u kafka --tail=50

    Sources: https://kafka.apache.org/documentation/#brokerconfigs

  2. 90% success Check advertised.listeners matches how clients reach the broker 
    In server.properties: advertised.listeners=PLAINTEXT://actual-hostname:9092  # must be routable from client
  3. 85% success Test connectivity from client machine 
    nc -zv broker-host 9092  # or: kafkacat -b broker-host:9092 -L

Dead Ends

Common approaches that don't work:

  1. Use the ZooKeeper address as bootstrap server 92% fail

    Clients connect to Kafka brokers, not ZooKeeper. ZooKeeper port (2181) is not the broker port (9092).

  2. Only check if broker is running and assume network is fine 75% fail

    advertised.listeners misconfiguration is the #1 cause in Docker/cloud. Broker runs fine but clients cannot reach the advertised address.