[jira] [Created] (KAFKA-3068) NetworkClient may connect to a different Kafka cluster than originally configured

["Jun Rao (JIRA)" <ji...@apache.org>]

Jun Rao created KAFKA-3068:
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             Summary: NetworkClient may connect to a different Kafka cluster than originally configured
                 Key: KAFKA-3068
                 URL: https://issues.apache.org/jira/browse/KAFKA-3068
             Project: Kafka
          Issue Type: Bug
          Components: clients
    Affects Versions: 0.9.0.0
            Reporter: Jun Rao


In https://github.com/apache/kafka/pull/290, we added the logic to cache all brokers (id and ip) that the client has ever seen. If we can't find an available broker from the current Metadata, we will pick a broker that we have ever seen (in NetworkClient.leastLoadedNode()).

One potential problem this logic can introduce is the following. Suppose that we have a broker with id 1 in a Kafka cluster. A producer client remembers this broker in nodesEverSeen. At some point, we bring down this broker and use the host in a different Kafka cluster. Then, the producer client uses this broker from nodesEverSeen to refresh metadata. It will find the metadata in a different Kafka cluster and start producing data there.



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