[jira] [Updated] (KAFKA-4405) Avoid calling pollNoWakeup unnecessarily

["Eno Thereska (JIRA)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/KAFKA-4405?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Eno Thereska updated KAFKA-4405:
--------------------------------
    Summary: Avoid calling pollNoWakeup unnecessarily  (was: Kafka consumer improperly send prefetch request)

> Avoid calling pollNoWakeup unnecessarily
> ----------------------------------------
>
>                 Key: KAFKA-4405
>                 URL: https://issues.apache.org/jira/browse/KAFKA-4405
>             Project: Kafka
>          Issue Type: Bug
>    Affects Versions: 0.10.0.1
>            Reporter: ysysberserk
>            Assignee: Eno Thereska
>             Fix For: 0.10.2.0
>
>
> Now kafka consumer has added max.poll.records to limit the count of messages return by poll().
> According to KIP-41, to implement  max.poll.records, the prefetch request should only be sent when the total number of retained records is less than max.poll.records.
> But in the code of 0.10.0.1 , the consumer will send a prefetch request if it retained any records and never check if total number of retained records is less than max.poll.records..
> If max.poll.records is set to a count much less than the count of message fetched , the poll() loop will send a lot of requests than expected and will have more and more records fetched and stored in memory before they can be consumed.
> So before sending a  prefetch request , the consumer must check if total number of retained records is less than max.poll.records.



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