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Posted to issues@spark.apache.org by "Ankur Dave (JIRA)" <ji...@apache.org> on 2014/09/23 00:07:34 UTC
[jira] [Updated] (SPARK-3649) ClassCastException in GraphX custom
serializers when sort-based shuffle spills
[ https://issues.apache.org/jira/browse/SPARK-3649?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]
Ankur Dave updated SPARK-3649:
------------------------------
Description:
As [reported|http://apache-spark-user-list.1001560.n3.nabble.com/java-lang-ClassCastException-java-lang-Long-cannot-be-cast-to-scala-Tuple2-td13926.html#a14501] on the mailing list, GraphX throws
{code}
java.lang.ClassCastException: java.lang.Long cannot be cast to scala.Tuple2
at org.apache.spark.graphx.impl.RoutingTableMessageSerializer$$anon$1$$anon$2.writeObject(Serializers.scala:39)
at org.apache.spark.storage.DiskBlockObjectWriter.write(BlockObjectWriter.scala:195)
at org.apache.spark.util.collection.ExternalSorter.spillToMergeableFile(ExternalSorter.scala:329)
{code}
when sort-based shuffle attempts to spill to disk. This is because GraphX defines custom serializers for shuffling pair RDDs that assume Spark will always serialize the entire pair object rather than breaking it up into its components. However, the spill code path in sort-based shuffle [violates this assumption|https://github.com/apache/spark/blob/f9d6220c792b779be385f3022d146911a22c2130/core/src/main/scala/org/apache/spark/util/collection/ExternalSorter.scala#L329].
GraphX uses the custom serializers to compress vertex ID keys using variable-length integer encoding. However, since the serializer can no longer rely on the key and value being serialized and deserialized together, performing such encoding would require writing a tag byte.
was:
As [reported|http://apache-spark-user-list.1001560.n3.nabble.com/java-lang-ClassCastException-java-lang-Long-cannot-be-cast-to-scala-Tuple2-td13926.html#a14501] on the mailing list, GraphX throws
{code}
java.lang.ClassCastException: java.lang.Long cannot be cast to scala.Tuple2
at org.apache.spark.graphx.impl.RoutingTableMessageSerializer$$anon$1$$anon$2.writeObject(Serializers.scala:39)
at org.apache.spark.storage.DiskBlockObjectWriter.write(BlockObjectWriter.scala:195)
at org.apache.spark.util.collection.ExternalSorter.spillToMergeableFile(ExternalSorter.scala:329)
{code}
when sort-based shuffle attempts to spill to disk. This is because GraphX defines custom serializers for shuffling pair RDDs that assume Spark will always serialize the entire pair object rather than breaking it up into its components. However, the spill code path in sort-based shuffle [violates this assumption|https://github.com/apache/spark/blob/f9d6220c792b779be385f3022d146911a22c2130/core/src/main/scala/org/apache/spark/util/collection/ExternalSorter.scala#L329].
> ClassCastException in GraphX custom serializers when sort-based shuffle spills
> ------------------------------------------------------------------------------
>
> Key: SPARK-3649
> URL: https://issues.apache.org/jira/browse/SPARK-3649
> Project: Spark
> Issue Type: Bug
> Components: GraphX
> Affects Versions: 1.2.0
> Reporter: Ankur Dave
> Assignee: Ankur Dave
>
> As [reported|http://apache-spark-user-list.1001560.n3.nabble.com/java-lang-ClassCastException-java-lang-Long-cannot-be-cast-to-scala-Tuple2-td13926.html#a14501] on the mailing list, GraphX throws
> {code}
> java.lang.ClassCastException: java.lang.Long cannot be cast to scala.Tuple2
> at org.apache.spark.graphx.impl.RoutingTableMessageSerializer$$anon$1$$anon$2.writeObject(Serializers.scala:39)
> at org.apache.spark.storage.DiskBlockObjectWriter.write(BlockObjectWriter.scala:195)
> at org.apache.spark.util.collection.ExternalSorter.spillToMergeableFile(ExternalSorter.scala:329)
> {code}
> when sort-based shuffle attempts to spill to disk. This is because GraphX defines custom serializers for shuffling pair RDDs that assume Spark will always serialize the entire pair object rather than breaking it up into its components. However, the spill code path in sort-based shuffle [violates this assumption|https://github.com/apache/spark/blob/f9d6220c792b779be385f3022d146911a22c2130/core/src/main/scala/org/apache/spark/util/collection/ExternalSorter.scala#L329].
> GraphX uses the custom serializers to compress vertex ID keys using variable-length integer encoding. However, since the serializer can no longer rely on the key and value being serialized and deserialized together, performing such encoding would require writing a tag byte.
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