[jira] [Updated] (FLINK-7347) "removeAll" is extremely inefficient in MessageAcknowledgingSourceBase.notifyCheckpointComplete

["Aljoscha Krettek (JIRA)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/FLINK-7347?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Aljoscha Krettek updated FLINK-7347:
------------------------------------
    Fix Version/s: 1.4.0

> "removeAll" is extremely inefficient in MessageAcknowledgingSourceBase.notifyCheckpointComplete
> -----------------------------------------------------------------------------------------------
>
>                 Key: FLINK-7347
>                 URL: https://issues.apache.org/jira/browse/FLINK-7347
>             Project: Flink
>          Issue Type: Improvement
>          Components: DataStream API
>    Affects Versions: 1.3.1
>            Reporter: Yonatan Most
>             Fix For: 1.4.0
>
>
> Observe this line in {{MessageAcknowledgingSourceBase.notifyCheckpointComplete}}:
> {code}
> idsProcessedButNotAcknowledged.removeAll(checkpoint.f1);
> {code}
> The implementation of {{removeAll}} is such that if the set is smaller than the collection to remove, then the set is iterated and every item is checked for containment in the collection. The type of {{checkpoint.f1}} here is {{ArrayList}}, so the {{contains}} action is very inefficient, and it is performed for every item in {{idsProcessedButNotAcknowledged}}.
> In our pipeline we had about 10 million events processed, and the checkpoint was stuck on the {{removeAll}} call for hours.
> A simple solution is to make {{idsForCurrentCheckpoint}} a {{HashSet}} instead of an {{ArrayList}}. The fact that it's a list is not really used anywhere.



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