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https://issues.apache.org/jira/browse/FLINK-8547?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16349921#comment-16349921
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ASF GitHub Bot commented on FLINK-8547:
---------------------------------------
GitHub user zhijiangW opened a pull request:
https://github.com/apache/flink/pull/5400
[FLINK-8547][network] Implement CheckpointBarrierHandler not to spill data
for exactly-once
## What is the purpose of the change
*Currently in exactly-once mode, the BarrierBuffer would block inputs with
barriers until all inputs have received the barrier for a given checkpoint. To
avoid back-pressuring the input streams which may cause distributed deadlocks,
the BarrierBuffer has to spill the data in disk files to recycle the buffers
for blocked channels.*
*Based on credit-based flow control, every channel has exclusive buffers,
so it is no need to spill data for avoiding deadlock. Then we implement a new
CheckpointBarrierHandler for only buffering the data for blocked channels for
better performance.*
*And this new CheckpointBarrierHandler can also be configured to use or not
in order to rollback the original mode for unexpected risks.*
## Brief change log
- *Implement the new `CreditBasedBarrierBuffer` and
`CreditBasedBufferBlocker` for buffering data in blocked channels in
exactly-once mode.*
- *Define the parameter `taskmanager.exactly-once.blocking.data.enabled`
for enabling the new handler or not.*
## Verifying this change
This change added tests and can be verified as follows:
- *Added tests for the logic of `CreditBasedBarrierBuffer`*
- *Added tests for the logic of `CreditBasedBufferBlocker`*
## 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)
- Anything that affects deployment or recovery: JobManager (and its
components), Checkpointing, Yarn/Mesos, ZooKeeper: (no)
- The S3 file system connector: (no)
## 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/zhijiangW/flink FLINK-8547
Alternatively you can review and apply these changes as the patch at:
https://github.com/apache/flink/pull/5400.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 #5400
----
commit 4d08e5d58c732e8f835016b48edc4494f8cb26fe
Author: Zhijiang <wangzhijiang999@...>
Date: 2018-02-02T07:45:49Z
[FLINK-8547][network] Implement CheckpointBarrierHandler not to spill data
for exactly-once
----
> Implement CheckpointBarrierHandler not to spill data for exactly-once based
> on credit-based flow control
> --------------------------------------------------------------------------------------------------------
>
> Key: FLINK-8547
> URL: https://issues.apache.org/jira/browse/FLINK-8547
> Project: Flink
> Issue Type: Sub-task
> Components: Network
> Affects Versions: 1.5.0
> Reporter: zhijiang
> Assignee: zhijiang
> Priority: Major
>
> Currently in exactly-once mode, the {{BarrierBuffer}} would block inputs with
> barriers until all inputs have received the barrier for a given checkpoint.
> To avoid back-pressuring the input streams which may cause distributed
> deadlocks, the {{BarrierBuffer}} has to spill the data in disk files to
> recycle the buffers for blocked channels.
>
> Based on credit-based flow control, every channel has exclusive buffers, so
> it is no need to spill data for avoiding deadlock. Then we implement a new
> {{CheckpointBarrierHandler}} for only buffering the data for blocked channels
> for better performance.
>
> And this new {{CheckpointBarrierHandler}} can also be configured to use or
> not in order to rollback the original mode for unexpected risks.
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