Ngone51 opened a new pull request #28257: [SPARK-31485][CORE] Avoid application 
hang if only partial barrier tasks launched
URL: https://github.com/apache/spark/pull/28257
 
 
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   ### What changes were proposed in this pull request?
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   Use `dagScheduler.taskSetFailed` to abort a barrier stage instead of 
throwing exception within `resourceOffers`.
   
   ### Why are the changes needed?
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   Any non fatal exception thrown within Spark RPC framework can be swallowed:
   
   
https://github.com/apache/spark/blob/100fc58da54e026cda87832a10e2d06eaeccdf87/core/src/main/scala/org/apache/spark/rpc/netty/Inbox.scala#L202-L211
   
    The method `TaskSchedulerImpl.resourceOffers` is also within the scope of 
Spark RPC framework. Thus, throw exception inside `resourceOffers` won't fail 
the application.
   
    As a result, if a barrier stage fail the require check at 
`require(addressesWithDescs.size == taskSet.numTasks, ...)`, the barrier stage 
will fail the check again and again util all tasks from `TaskSetManager` 
dequeued.   But since the barrier stage isn't really executed, the application 
will hang.
   
   The issue can be reproduced by the following test:
   
   ```scala
   initLocalClusterSparkContext(2)
   val rdd0 = sc.parallelize(Seq(0, 1, 2, 3), 2)
   val dep = new OneToOneDependency[Int](rdd0)
   val rdd = new MyRDD(sc, 2, List(dep), 
Seq(Seq("executor_h_0"),Seq("executor_h_0")))
   rdd.barrier().mapPartitions { iter =>
     BarrierTaskContext.get().barrier()
     iter
   }.collect()
   ```
   
   ### Does this PR introduce any user-facing change?
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   Yes, application hang previously but fail-fast after this fix.
   
   ### How was this patch tested?
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   Added a regression test.

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