[jira] [Created] (SPARK-25283) A deadlock in UnionRDD

["Maxim Gekk (JIRA)" <ji...@apache.org>]

Maxim Gekk created SPARK-25283:
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             Summary: A deadlock in UnionRDD
                 Key: SPARK-25283
                 URL: https://issues.apache.org/jira/browse/SPARK-25283
             Project: Spark
          Issue Type: Bug
          Components: Spark Core
    Affects Versions: 2.4.0
            Reporter: Maxim Gekk


The PR https://github.com/apache/spark/pull/21913 replaced Scala parallel collections in UnionRDD by new parmap function. This changes cause a deadlock in the partitions method. The code demonstrates the problem:
{code:scala}
    val wide = 20
    def unionRDD(num: Int): UnionRDD[Int] = {
      val rdds = (0 until num).map(_ => sc.parallelize(1 to 10, 1))
      new UnionRDD(sc, rdds)
    }
    val level0 = (0 until wide).map { _ =>
      val level1 = (0 until wide).map(_ => unionRDD(wide))
      new UnionRDD(sc, level1)
    }
    val rdd = new UnionRDD(sc, level0)

    rdd.partitions.length
{code}




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