advancedxy commented on a change in pull request #23638: [SPARK-26713][CORE]
Interrupt pipe IO threads in PipedRDD when task is finished
URL: https://github.com/apache/spark/pull/23638#discussion_r250855785
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File path: core/src/main/scala/org/apache/spark/rdd/PipedRDD.scala
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@@ -156,7 +157,32 @@ private[spark] class PipedRDD[T: ClassTag](
out.close()
}
}
- }.start()
+ }
+ stdinWriterThread.start()
+
+ // interrupts stdin writer and stderr read threads when the corresponding
task is finished as a
+ // safe belt. Otherwise, these threads could outlive the task's lifetime.
For example:
+ // val pipeRDD = sc.range(1, 100).pipe(Seq("cat"))
+ // val abnormalRDD = pipeRDD.mapPartitions(_ => Iterator.empty)
+ // the iterator generated by PipedRDD is never involved. If the parent
RDD's iterator is time
+ // consuming to generate(ShuffledRDD's shuffle operation for example), the
outlived stdin writer
+ // thread will consume significant memory and cpu time. Also, there's race
condition for
Review comment:
This is a tricky one. After the fix in this pr to
`ShuffleBlockFetcherIterator`, the race condition should be really rare as only
one potential next call may hang. However I am unable to find a good place to
put the above comment in `ShuffleBlockFetcherIterator`. So it's inside this
`task completion listener`.
Do you have any suggestion?
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