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https://issues.apache.org/jira/browse/FLINK-9635?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16667366#comment-16667366
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ASF GitHub Bot commented on FLINK-9635:
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StefanRRichter opened a new pull request #6961: [FLINK-9635] Fix scheduling for
local recovery
URL: https://github.com/apache/flink/pull/6961
## What is the purpose of the change
This change fixes the task spread-out problem in scheduling with local
recovery. The solution is based on creating a global set of all previous
allocation ids as blacklist to avoid, but all other allocation ids are now free
to take again.
## Brief change log
This PR contains a subset of the changes from #6898 and focuses almost
purely on the fix of local recovery.
## Verifying this change
Improved `SchedulingITCase` should work now, including previously ignored
tests.
## 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): (no)
- 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)
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> Local recovery scheduling can cause spread out of tasks
> -------------------------------------------------------
>
> Key: FLINK-9635
> URL: https://issues.apache.org/jira/browse/FLINK-9635
> Project: Flink
> Issue Type: Bug
> Components: Distributed Coordination
> Affects Versions: 1.5.0, 1.6.2
> Reporter: Till Rohrmann
> Assignee: Stefan Richter
> Priority: Critical
> Labels: pull-request-available
> Fix For: 1.7.0
>
>
> In order to make local recovery work, Flink's scheduling was changed such
> that it tries to be rescheduled to its previous location. In order to not
> occupy slots which have state of other tasks cached, the strategy will
> request a new slot if the old slot identified by the previous allocation id
> is no longer present. This also applies to newly allocated slots because
> there is no distinction between new or already used. This behaviour can cause
> that every tasks gets deployed to its own slot if the {{SlotPool}} has
> released all slots in the meantime, for example. The consequence could be
> that a job can no longer be executed after a failure because it needs more
> slots than before.
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