Critical Description
In Kraft mode Apache Kafka 2.8.0 does advertise the socket port instead of the configured advertised port.
A broker given with the following configuration
listeners=PUBLIC://0.0.0.0:19092,REPLICATION://0.0.0.0:9091 advertised.listeners=PUBLIC://envoy-kafka-broker:9091,REPLICATION://kafka-broker1:9091
advertises on the PUBLIC listener envoy-kafka-broker:19092, however I would expect that envoy-kafka-broker:9091 is advertised. In ZooKeeper mode it works as expected.
In a deployment with a L4 proxy in front of the Kafka cluster, it is important, that the advertised port can be different from the actual socket port.
I tested it with a Docker-Compose setup which runs 3 Kafka Broker in Kraft mode and an Envoy proxy in front of them. With Apache Kafka 2.8.0 it does not work, because Kafka does not advertise the configured advertised port. For more details see: https://github.com/ueisele/kafka/tree/fix/kraft-advertisedlisteners-build/proxy-examples/proxyl4-kafkakraft-bug-2.8
Client – 909[1-3] --> Envoy Proxy – 19092 --> Kafka Broker [1-3]
| Envoy Host | Envoy Port | Kafka Broker | Kafka Port | Advertised Listener |
|---|---|---|---|---|
| envoy-kafka-broker | 9091 | kafka-broker1 | 19092 | envoy-kafka-broker:9091 |
| envoy-kafka-broker | 9092 | kafka-broker2 | 19092 | envoy-kafka-broker:9092 |
| envoy-kafka-broker | 9093 | kafka-broker3 | 19092 | envoy-kafka-broker:9093 |
> docker-compose exec kafkacat kafkacat -b envoy-kafka-broker:9091 -L
Metadata for all topics (from broker -1: envoy-kafka-broker:9091/bootstrap):
3 brokers:
broker 101 at envoy-kafka-broker:19092
broker 102 at envoy-kafka-broker:19092 (controller)
broker 103 at envoy-kafka-broker:19092
0 topics:
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