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https://issues.apache.org/jira/browse/FLINK-7347?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16112347#comment-16112347
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ASF GitHub Bot commented on FLINK-7347:
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GitHub user ymost opened a pull request:
https://github.com/apache/flink/pull/4468
[FLINK-7347] [streaming] Keep ids for current checkpoint in a set instead
of a list
JIRA issue: FLINK-7347
## What is the purpose of the change
This pull request changes the data structure used to store
acknowledge-pending message ids from an `ArrayList` to a `HashSet`. This is
done to eliminate an extremely inefficient call to the `removeAll` method in
`MessageAcknowledgingSourceBase.notifyCheckpointComplete`.
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 `contains` action on an `ArrayList` is
very inefficient, and it is performed for every item the set.
In our pipeline we had about 10 million events processed, and the
checkpoint was stuck on the `removeAll` call for hours.
## Brief change log
Keep ids for current checkpoint in a set instead of a list
## Verifying this change
This change is already covered by existing tests, such as `RMQSourceTest`.
## Does this pull request potentially affect one of the following parts:
- Dependencies (does it add or upgrade a dependency): **no**
- The public API, i.e., is any changed class annotated with
`@Public(Evolving)`: **no**
- The serializers: **no**
- The runtime per-record code paths (performance sensitive): **yes** -
performance should be improved
- Anything that affects deployment or recovery: JobManager (and its
components), Checkpointing, Yarn/Mesos, ZooKeeper: **yes** - this should
resolve the problem where checkpoints would get stuck on the call to `removeAll`
## Documentation
- Does this pull request introduce a new feature? **no**
- If yes, how is the feature documented? **not applicable**
You can merge this pull request into a Git repository by running:
$ git pull https://github.com/ymost/flink FLINK-7347-checkpoint-ids-set
Alternatively you can review and apply these changes as the patch at:
https://github.com/apache/flink/pull/4468.patch
To close this pull request, make a commit to your master/trunk branch
with (at least) the following in the commit message:
This closes #4468
----
----
> "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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