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https://issues.apache.org/jira/browse/SPARK-22465?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Apache Spark reassigned SPARK-22465:
------------------------------------
Assignee: Apache Spark
> Cogroup of two disproportionate RDDs could lead into 2G limit BUG
> -----------------------------------------------------------------
>
> Key: SPARK-22465
> URL: https://issues.apache.org/jira/browse/SPARK-22465
> Project: Spark
> Issue Type: Bug
> Components: Spark Core
> Affects Versions: 1.0.0, 1.0.1, 1.0.2, 1.1.0, 1.1.1, 1.2.0, 1.2.1, 1.2.2,
> 1.3.0, 1.3.1, 1.4.0, 1.4.1, 1.5.0, 1.5.1, 1.5.2, 1.6.0, 1.6.1, 1.6.2, 1.6.3,
> 2.0.0, 2.0.1, 2.0.2, 2.1.0, 2.1.1, 2.1.2, 2.2.0
> Reporter: Amit Kumar
> Assignee: Apache Spark
> Priority: Critical
>
> While running my spark pipeline, it failed with the following exception
> {noformat}
> 2017-11-03 04:49:09,776 [Executor task launch worker for task 58670] ERROR
> org.apache.spark.executor.Executor - Exception in task 630.0 in stage 28.0
> (TID 58670)
> java.lang.IllegalArgumentException: Size exceeds Integer.MAX_VALUE
> at sun.nio.ch.FileChannelImpl.map(FileChannelImpl.java:869)
> at
> org.apache.spark.storage.DiskStore$$anonfun$getBytes$2.apply(DiskStore.scala:103)
> at
> org.apache.spark.storage.DiskStore$$anonfun$getBytes$2.apply(DiskStore.scala:91)
> at org.apache.spark.util.Utils$.tryWithSafeFinally(Utils.scala:1303)
> at org.apache.spark.storage.DiskStore.getBytes(DiskStore.scala:105)
> at
> org.apache.spark.storage.BlockManager.getLocalValues(BlockManager.scala:469)
> at
> org.apache.spark.storage.BlockManager.getOrElseUpdate(BlockManager.scala:705)
> at org.apache.spark.rdd.RDD.getOrCompute(RDD.scala:334)
> at org.apache.spark.rdd.RDD.iterator(RDD.scala:285)
> at org.apache.spark.scheduler.ResultTask.runTask(ResultTask.scala:87)
> at org.apache.spark.scheduler.Task.run(Task.scala:99)
> at org.apache.spark.executor.Executor$TaskRunner.run(Executor.scala:324)
> at
> java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
> at
> java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
> at java.lang.Thread.run(Thread.java:745)
> {noformat}
> After debugging I found that the issue lies with how spark handles cogroup of
> two RDDs.
> Here is the relevant code from apache spark
> {noformat}
> /**
> * For each key k in `this` or `other`, return a resulting RDD that
> contains a tuple with the
> * list of values for that key in `this` as well as `other`.
> */
> def cogroup[W](other: RDD[(K, W)]): RDD[(K, (Iterable[V], Iterable[W]))] =
> self.withScope {
> cogroup(other, defaultPartitioner(self, other))
> }
> /**
> * Choose a partitioner to use for a cogroup-like operation between a
> number of RDDs.
> *
> * If any of the RDDs already has a partitioner, choose that one.
> *
> * Otherwise, we use a default HashPartitioner. For the number of
> partitions, if
> * spark.default.parallelism is set, then we'll use the value from
> SparkContext
> * defaultParallelism, otherwise we'll use the max number of upstream
> partitions.
> *
> * Unless spark.default.parallelism is set, the number of partitions will
> be the
> * same as the number of partitions in the largest upstream RDD, as this
> should
> * be least likely to cause out-of-memory errors.
> *
> * We use two method parameters (rdd, others) to enforce callers passing at
> least 1 RDD.
> */
> def defaultPartitioner(rdd: RDD[_], others: RDD[_]*): Partitioner = {
> val rdds = (Seq(rdd) ++ others)
> val hasPartitioner = rdds.filter(_.partitioner.exists(_.numPartitions >
> 0))
> if (hasPartitioner.nonEmpty) {
> hasPartitioner.maxBy(_.partitions.length).partitioner.get
> } else {
> if (rdd.context.conf.contains("spark.default.parallelism")) {
> new HashPartitioner(rdd.context.defaultParallelism)
> } else {
> new HashPartitioner(rdds.map(_.partitions.length).max)
> }
> }
> }
> {noformat}
> Given this suppose we have two pair RDDs.
> RDD1 : A small RDD which fewer data and partitions
> RDD2: A huge RDD which has loads of data and partitions
> Now in the code if we were to have a cogroup
> {noformat}
> val RDD3 = RDD1.cogroup(RDD2)
> {noformat}
> there is a case where this could lead to the SPARK-6235 Bug which is If RDD1
> has a partitioner when it is being called into a cogroup. This is because the
> cogroups partitions are then decided by the partitioner and could lead to the
> huge RDD2 being shuffled into a small number of partitions.
> One way is probably to add a safety check here that would ignore the
> partitioner if the number of partitions on the two RDDs are very different in
> magnitude.
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