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https://issues.apache.org/jira/browse/KAFKA-4405?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15705475#comment-15705475
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Eno Thereska commented on KAFKA-4405:
-------------------------------------
[~guozhang], [~hachikuji]
Indeed I can verify that I saw a 50% increase in performance with
max.poll.records set to 1 with [~ysysberserk]'s suggestion in
KafkaConsumer::poll()
// 1 line change. For testing, I made fetcher.maxPollRecords
public.
if (records.size() < fetcher.maxPollRecords){
fetcher.sendFetches();
client.pollNoWakeup();
}
> Kafka consumer improperly send prefetch request
> -----------------------------------------------
>
> 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
>
> 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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