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https://issues.apache.org/jira/browse/FLINK-28838?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17576824#comment-17576824
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Aitozi commented on FLINK-28838:
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cc [~renqs] could you help take a look ?
> Avoid to notify the elementQueue consumer when the fetch result is empty
> ------------------------------------------------------------------------
>
> Key: FLINK-28838
> URL: https://issues.apache.org/jira/browse/FLINK-28838
> Project: Flink
> Issue Type: Improvement
> Components: Connectors / Common
> Affects Versions: 1.15.0, 1.15.1
> Reporter: Aitozi
> Priority: Major
> Fix For: 1.16.0
>
> Attachments: 20220805165441.jpg
>
>
> When using the new source api, I found that if the source has no data, it
> still brings high cpu usage.
> The reason behind this is that it will always return the
> {{RecordsWithSplitIds}} from the {{splitReader.fetch}} in FetchTask and it
> will be added to the elementQueue. It will make the consumer be notified to
> wake up frequently.
> This causes the thread to keep busy to run and wake up, which leads to the
> high sys and user cpu usage.
> I think not all the SplitReader#fetch will block until there is data, if it
> returns immediately when there is no data, then this problem will happen
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