[jira] [Commented] (KAFKA-6297) Consumer fetcher should handle UnsupportedVersionException more diligently

["Colin P. McCabe (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/KAFKA-6297?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16275304#comment-16275304 ] 

Colin P. McCabe commented on KAFKA-6297:
----------------------------------------

Good find.  We need to make sure we have this coverage in the system tests, too...

> Consumer fetcher should handle UnsupportedVersionException more diligently
> --------------------------------------------------------------------------
>
>                 Key: KAFKA-6297
>                 URL: https://issues.apache.org/jira/browse/KAFKA-6297
>             Project: Kafka
>          Issue Type: Bug
>          Components: consumer
>            Reporter: Guozhang Wang
>
> Today if the consumer is talking to an older versioned broker that does not support newer fetch versions, it will simply block without printing any warning logs. This is because when {{UnsupportedVersionException}} gets raised inside {{ConsumerNetworkClient}}, the {{Fetcher}}'s handling logic is only logging it and moves on (and hence retries forever):
> {code}
>                        @Override
>                         public void onFailure(RuntimeException e) {
>                             log.debug("Fetch request {} to {} failed", request.fetchData(), fetchTarget, e);
>                         }
> {code}
> We should at least logging {{UnsupportedVersionException}} specifically as WARN or even let the consumer to fail fast and gracefully upon this error.
> Side note: There are two system tests in {{streams_broker_compatibility_test.ps}} that are disabled atm -- after this got fixed, we need to re-enable those tests (and also update them accordingly). 



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