[jira] [Created] (KAFKA-8607) Reduce AdminClient Metadata request rate when invalid node id is given

["Stanislav Kozlovski (JIRA)" <ji...@apache.org>]

Stanislav Kozlovski created KAFKA-8607:
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             Summary: Reduce AdminClient Metadata request rate when invalid node id is given
                 Key: KAFKA-8607
                 URL: https://issues.apache.org/jira/browse/KAFKA-8607
             Project: Kafka
          Issue Type: Task
    Affects Versions: 2.3.0, 2.2.0, 2.1.0, 2.0.0
            Reporter: Stanislav Kozlovski


While testing KAFKA-7800 (KIP-412), we were playing around with the config command CLI and [noticed that it hangs for very long|https://github.com/apache/kafka/pull/6903#discussion_r297434016] when given an invalid broker id.

After investigating a bit more, I noticed that we endlessly retry metadata updates. Locally, my AdminClient issued 78 requests for 10 seconds - averaging at a rate of 7.8 requests/sec. The call times out after 2 minutes by default - we end up sending 1149 requests.



This respects the "retry.backoff.ms" config  but it may be better to have some sort of exponential backoff to ease the needless load on the cluster.
It is unlikely for this to be a high-impact change but it sounds worth it to have the protection. Orchestration systems like Kubernetes make it easier for a user to mass-deploy a wrong config and inadvertenly DDoS his cluster via metadata requests



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