[jira] [Resolved] (SPARK-15002) Calling unpersist can cause spark to hang indefinitely when writing out a result

["Hyukjin Kwon (JIRA)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/SPARK-15002?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Hyukjin Kwon resolved SPARK-15002.
----------------------------------
    Resolution: Incomplete

> Calling unpersist can cause spark to hang indefinitely when writing out a result
> --------------------------------------------------------------------------------
>
>                 Key: SPARK-15002
>                 URL: https://issues.apache.org/jira/browse/SPARK-15002
>             Project: Spark
>          Issue Type: Bug
>          Components: GraphX, Spark Core
>    Affects Versions: 1.5.2, 1.6.0, 2.0.0
>         Environment: AWS and Linux VM, both in spark-shell and spark-submit. tested in 1.5.2 and 1.6. Tested in 2.0
>            Reporter: Jamie Hutton
>            Priority: Major
>              Labels: bulk-closed
>
> The following code will cause spark to hang indefinitely. It happens when you have an unpersist which is followed by some futher processing of that data (in my case writing it out).
> I first experienced this issue with graphX so my example below involved graphX code, however i suspect it might be more of a core issue than a graphx one. I have raised another bug with similar results (indefinite hanging) but in different circumstances, so these may well be linked
> Code to reproduce (can be run in spark-shell):
> import org.apache.spark.graphx._
> import org.apache.spark.rdd.RDD
> import org.apache.spark.sql.types._
> import org.apache.spark.sql._
> val r = scala.util.Random
> val list = (0L to 500L).map(i=>(i,r.nextInt(500).asInstanceOf[Long],"LABEL"))
> val distData = sc.parallelize(list)
> val edgesRDD = distData.map(x => Edge(x._1, x._2, x._3))
> val distinctNodes = distData.flatMap{row => Iterable((row._1, ("A")),(row._2, ("B")))}.distinct()
> val nodesRDD: RDD[(VertexId, (String))] = distinctNodes
> val graph = Graph(nodesRDD, edgesRDD)
> graph.persist()
> val ccGraph = graph.connectedComponents()
> ccGraph.cache
>    
> val schema = StructType(Seq(StructField("id", LongType, false), StructField("netid", LongType, false)))
> val rdd=ccGraph.vertices.map(row=>(Row(row._1.asInstanceOf[Long],row._2.asInstanceOf[Long])))
> val builtEntityDF = sqlContext.createDataFrame(rdd, schema)
>  
> /*this unpersist step causes the issue*/
> ccGraph.unpersist()
>  
> /*write step hangs for ever*/
> builtEntityDF.write.format("parquet").mode("overwrite").save("/user/root/writetest.parquet") 
> If you take out the ccGraph.unpersist() step the write step completes successfully



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