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https://issues.apache.org/jira/browse/SPARK-7002?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14509933#comment-14509933
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Sean Owen commented on SPARK-7002:
----------------------------------
[~thubregtsen] Just open a PR for this JIRA. You can modify the title /
priority / etc here as you see fit to reflect the new goal.
> Persist on RDD fails the second time if the action is called on a child RDD
> without showing a FAILED message
> ------------------------------------------------------------------------------------------------------------
>
> Key: SPARK-7002
> URL: https://issues.apache.org/jira/browse/SPARK-7002
> Project: Spark
> Issue Type: Bug
> Components: Spark Core
> Affects Versions: 1.3.0
> Environment: Platform: Power8
> OS: Ubuntu 14.10
> Java: java-8-openjdk-ppc64el
> Reporter: Tom Hubregtsen
> Priority: Minor
> Labels: disk, persist, unpersist
>
> The major issue is: Persist on RDD fails the second time if the action is
> called on a child RDD without showing a FAILED message. This is pointed out
> at 2)
> next to this:
> toDebugString on a child RDD does not show that the parent RDD is [Disk
> Serialized 1x Replicated]. This is pointed out at 1)
> Note: I am persisting to disk (DISK_ONLY) to validate that the RDD is or is
> not physically stored, as I did not want to solely rely on a missing line in
> .toDebugString (see comments in trace)
> {code}
> scala> val rdd1 = sc.parallelize(List(1,2,3))
> scala> val rdd2 = rdd1.map(x => (x,x+1))
> scala> val rdd3 = rdd2.reduceByKey( (x,y) => x+y)
> scala> import org.apache.spark.storage.StorageLevel
> scala> rdd2.persist(StorageLevel.DISK_ONLY)
> scala> rdd3.collect()
> scala> rdd2.toDebugString
> res4: String =
> (100) MapPartitionsRDD[1] at map at <console>:23 [Disk Serialized 1x
> Replicated]
> \| CachedPartitions: 100; MemorySize: 0.0 B; TachyonSize: 0.0 B;
> DiskSize: 802.0 B
> \| ParallelCollectionRDD[0] at parallelize at <console>:21 [Disk
> Serialized 1x Replicated]
> scala> rdd3.toDebugString
> res5: String =
> (100) ShuffledRDD[2] at reduceByKey at <console>:25 []
> +-(100) MapPartitionsRDD[1] at map at <console>:23 []
> \| CachedPartitions: 100; MemorySize: 0.0 B; TachyonSize: 0.0 B;
> DiskSize: 802.0 B
> \| ParallelCollectionRDD[0] at parallelize at <console>:21 []
> // 1) rdd3 does not show that the other RDD's are [Disk Serialized 1x
> Replicated], but the data is on disk. This is verified by
> // a) The line starting with CachedPartitions
> // b) a find in spark_local_dir: "find . -name "\*" \| grep rdd" returns
> "./spark-b39bcf9b-e7d7-4284-bdd2-1be7ac3cacef/blockmgr-4f4c0b1c-b47a-4972-b364-7179ea6e0873/1f/rdd_4_*",
> where * are the number of partitions
> scala> rdd2.unpersist()
> scala> rdd2.toDebugString
> res8: String =
> (100) MapPartitionsRDD[1] at map at <console>:23 []
> \| ParallelCollectionRDD[0] at parallelize at <console>:21 []
> scala> rdd3.toDebugString
> res9: String =
> (100) ShuffledRDD[2] at reduceByKey at <console>:25 []
> +-(100) MapPartitionsRDD[1] at map at <console>:23 []
> \| ParallelCollectionRDD[0] at parallelize at <console>:21 []
> // successfully unpersisted, also not visible on disk
> scala> rdd2.persist(StorageLevel.DISK_ONLY)
> scala> rdd3.collect()
> scala> rdd2.toDebugString
> res18: String =
> (100) MapPartitionsRDD[1] at map at <console>:23 [Disk Serialized 1x
> Replicated]
> \| ParallelCollectionRDD[0] at parallelize at <console>:21 [Disk
> Serialized 1x Replicated]
> scala> rdd3.toDebugString
> res19: String =
> (100) ShuffledRDD[2] at reduceByKey at <console>:25 []
> +-(100) MapPartitionsRDD[1] at map at <console>:23 []
> \| ParallelCollectionRDD[0] at parallelize at <console>:21 []
> // 2) The data is not visible on disk though the find command previously
> mentioned, and is also not mentioned in the toDebugString (no line starting
> with CachedPartitions, even though [Disk Serialized 1x Replicated] is
> mentioned). It does work when you call the action on the actual RDD:
> scala> rdd2.collect()
> scala> rdd2.toDebugString
> res21: String =
> (100) MapPartitionsRDD[1] at map at <console>:23 [Disk Serialized 1x
> Replicated]
> \| CachedPartitions: 100; MemorySize: 0.0 B; TachyonSize: 0.0 B;
> DiskSize: 802.0 B
> \| ParallelCollectionRDD[0] at parallelize at <console>:21 [Disk
> Serialized 1x Replicated]
> scala> rdd3.toDebugString
> res22: String =
> (100) ShuffledRDD[2] at reduceByKey at <console>:25 []
> +-(100) MapPartitionsRDD[1] at map at <console>:23 []
> \| CachedPartitions: 100; MemorySize: 0.0 B; TachyonSize: 0.0 B;
> DiskSize: 802.0 B
> \| ParallelCollectionRDD[0] at parallelize at <console>:21 []
> // Data appears on disk again (using find command preciously mentioned), and
> line with CachedPartitions is back in the .toDebugString
> {code}
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