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https://issues.apache.org/jira/browse/SPARK-24375?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16516411#comment-16516411
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Mridul Muralidharan commented on SPARK-24375:
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[~jiangxb1987] A couple of comments based on the document and your elaboration 
above:

* Is the 'barrier' logic pluggable ? Instead of only being a global sync point.
* Dynamic resource allocation (dra) triggers allocation of additional resources 
based on pending tasks - hence *We may add a check of total available slots 
before scheduling tasks from a barrier stage taskset.* does not necessarily 
work in that context.
* Currently DRA in spark uniformly allocates resources - are we envisioning 
changes as part of this effort to allocate heterogenous executor resources 
based on pending tasks (atleast initially for barrier support for gpu's) ?
* How is fault tolerance handled w.r.t waiting on incorrect barriers ? Any way 
to identify the barrier ? Example:
{code}
try {
  ... snippet A ...
  // Barrier 1
  context.barrier()
  ... snippet B ...
} catch { ... }
... snippet C ...
// Barrier 2
context.barrier()

{code}
** In face of exceptions, some tasks will wait on barrier 2 and others on 
barrier 1 : causing issues.
*

> Design sketch: support barrier scheduling in Apache Spark
> ---------------------------------------------------------
>
>                 Key: SPARK-24375
>                 URL: https://issues.apache.org/jira/browse/SPARK-24375
>             Project: Spark
>          Issue Type: Story
>          Components: Spark Core
>    Affects Versions: 3.0.0
>            Reporter: Xiangrui Meng
>            Assignee: Jiang Xingbo
>            Priority: Major
>
> This task is to outline a design sketch for the barrier scheduling SPIP 
> discussion. It doesn't need to be a complete design before the vote. But it 
> should at least cover both Scala/Java and PySpark.



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