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https://issues.apache.org/jira/browse/KAFKA-4429?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15791770#comment-15791770
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Dong Lin commented on KAFKA-4429:
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[~kevinconaway] Receiving an empty FetchReponse is different from not receiving
any fetch response. I agree with you that we can use positive (Min) if no value
is present. But for this ticket, if the client receives an empty FetchResponse,
the lag should be zero because there is no new data available.
> records-lag should be zero if FetchResponse is empty
> ----------------------------------------------------
>
> Key: KAFKA-4429
> URL: https://issues.apache.org/jira/browse/KAFKA-4429
> Project: Kafka
> Issue Type: Improvement
> Reporter: Dong Lin
> Assignee: Dong Lin
>
> In Fetcher we record records-lag in terms of number of records for any
> partition. Currently this metric value is updated only if number of parsed
> records is not empty. This means that if consumer has already fully caught up
> and there is no new data into the topic, this metric's value will be negative
> infinity and users can not rely on this metric to know if their consumer has
> caught up.
> We can fix this problem by assuming the lag is zero is FetchResponse is empty.
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