Yonatan Most created FLINK-7347:
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Summary: "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
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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