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From "ASF GitHub Bot (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (FLINK-7231) SlotSharingGroups are not always released in time for new restarts
Date Wed, 19 Jul 2017 16:37:00 GMT

    [ https://issues.apache.org/jira/browse/FLINK-7231?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16093378#comment-16093378

ASF GitHub Bot commented on FLINK-7231:

GitHub user StephanEwen opened a pull request:


    [FLINK-7231] [distr. coordination] Fix slot release affecting SlotSharingGroup cleanup

    **This is base on #4364 so only the last commit is relevant**
    ## What is the purpose of the change
    This fixes [FLINK-7231](https://issues.apache.org/jira/browse/FLINK-7231) - a bug making
restarts unstable in the presence of certain combination of slot sharing, losses of TaskManagers,
and restart strategies.
    ## Brief change log
      - Minimal adjustment in `ExecutionGraph`: On failed resource acquisition, release slots
(and with that sharing group assignments) before triggering the recovery. Before this change,
both happened concurrently/asynchronously (and recovery may have overtaken slot release).
    ## Verifying this change
    This change adds additional unit tests:
      - `ExecutionGraphRestartTest#testRestartWithEagerSchedulingAndSlotSharing()`
      - `ExecutionGraphRestartTest#testRestartWithSlotSharingAndNotEnoughResources()`
    The effect (and fix) can also be observed by repeatedly trying the following:
      - Create a streaming job with multiple JobVertices
      - Set the restart strategy to fixed-delay with zero delay
      - Run the job
      - Repeat: Kill TaskManager and bring up recovery TaskManager. There is a good chance
that various restarts are affected by `java.lang.IllegalStateException: SlotSharingGroup cannot
clear task assignment, group still has allocated resources.`, meaning they take long before
actually recovering.
    ## 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: **yes**
    ## 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/StephanEwen/incubator-flink sharing_group_bug

Alternatively you can review and apply these changes as the patch at:


To close this pull request, make a commit to your master/trunk branch
with (at least) the following in the commit message:

    This closes #4370
commit f055645b3d905ea212b11eb570926d46447f3f52
Author: zjureel <zjureel@gmail.com>
Date:   2017-07-18T17:27:56Z

    [FLINK-6665] [FLINK-6667] [distributed coordination] Use a callback and a ScheduledExecutor
for ExecutionGraph restarts
    Initial work by zjureel@gmail.com , improved by sewen@apache.org.

commit 11e2144892a57c58ffe919ac228c702595f34025
Author: Stephan Ewen <sewen@apache.org>
Date:   2017-07-18T17:49:56Z

    [FLINK-7216] [distr. coordination] Guard against concurrent global failover

commit 16e9e133e0ed9dfba2d177c8f789f1b215a7759e
Author: Stephan Ewen <sewen@apache.org>
Date:   2017-07-19T08:24:52Z

    [FLINK-7231] [distr. coordination] Fix slot release affecting SlotSharingGroup cleanup


> SlotSharingGroups are not always released in time for new restarts
> ------------------------------------------------------------------
>                 Key: FLINK-7231
>                 URL: https://issues.apache.org/jira/browse/FLINK-7231
>             Project: Flink
>          Issue Type: Bug
>          Components: Distributed Coordination
>    Affects Versions: 1.3.1
>            Reporter: Stephan Ewen
>            Assignee: Stephan Ewen
>             Fix For: 1.4.0, 1.3.2
> In the case where there are not enough resources to schedule the streaming program, a
race condition can lead to a sequence of the following errors:
> {code}
> java.lang.IllegalStateException: SlotSharingGroup cannot clear task assignment, group
still has allocated resources.
> {code}
> This eventually recovers, but may involve many fast restart attempts before doing so.
> The root cause is that slots are not cleared before the next restart attempt.

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