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From "Dong Lin (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (KAFKA-4429) records-lag should be zero if FetchResponse is empty
Date Sun, 01 Jan 2017 22:37:58 GMT

    [ https://issues.apache.org/jira/browse/KAFKA-4429?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15791770#comment-15791770

Dong Lin commented on KAFKA-4429:

[~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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