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https://issues.apache.org/jira/browse/SPARK-3926?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Sean Owen reopened SPARK-3926:
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I am reopening as it is not actually serializable without a no-arg constructor.
PR coming shortly, that copies the implementation from Scala's
Wrappers.MapWrapper.
> result of JavaRDD collectAsMap() is not serializable
> ----------------------------------------------------
>
> Key: SPARK-3926
> URL: https://issues.apache.org/jira/browse/SPARK-3926
> Project: Spark
> Issue Type: Bug
> Components: Java API
> Affects Versions: 1.0.2, 1.1.0, 1.2.0
> Environment: CentOS / Spark 1.1 / Hadoop Hortonworks 2.4.0.2.1.2.0-402
> Reporter: Antoine Amend
> Assignee: Sean Owen
> Fix For: 1.1.1, 1.2.0
>
>
> Using the Java API, I want to collect the result of a RDD<String, String> as
> a HashMap using collectAsMap function:
> Map<String, String> map = myJavaRDD.collectAsMap();
> This works fine, but when passing this map to another function, such as...
> myOtherJavaRDD.mapToPair(new CustomFunction(map))
> ...this leads to the following error:
> Exception in thread "main" org.apache.spark.SparkException: Task not
> serializable
> at
> org.apache.spark.util.ClosureCleaner$.ensureSerializable(ClosureCleaner.scala:166)
> at org.apache.spark.util.ClosureCleaner$.clean(ClosureCleaner.scala:158)
> at org.apache.spark.SparkContext.clean(SparkContext.scala:1242)
> at org.apache.spark.rdd.RDD.map(RDD.scala:270)
> at
> org.apache.spark.api.java.JavaRDDLike$class.mapToPair(JavaRDDLike.scala:99)
> at org.apache.spark.api.java.JavaPairRDD.mapToPair(JavaPairRDD.scala:44)
> ../.. MY CLASS ../..
> at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
> at
> sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
> at
> sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
> at java.lang.reflect.Method.invoke(Method.java:606)
> at org.apache.spark.deploy.SparkSubmit$.launch(SparkSubmit.scala:328)
> at org.apache.spark.deploy.SparkSubmit$.main(SparkSubmit.scala:75)
> at org.apache.spark.deploy.SparkSubmit.main(SparkSubmit.scala)
> Caused by: java.io.NotSerializableException:
> scala.collection.convert.Wrappers$MapWrapper
> at java.io.ObjectOutputStream.writeObject0(ObjectOutputStream.java:1183)
> at
> java.io.ObjectOutputStream.defaultWriteFields(ObjectOutputStream.java:1547)
> at
> java.io.ObjectOutputStream.writeSerialData(ObjectOutputStream.java:1508)
> at
> java.io.ObjectOutputStream.writeOrdinaryObject(ObjectOutputStream.java:1431)
> at java.io.ObjectOutputStream.writeObject0(ObjectOutputStream.java:1177)
> at
> java.io.ObjectOutputStream.defaultWriteFields(ObjectOutputStream.java:1547)
> at
> java.io.ObjectOutputStream.writeSerialData(ObjectOutputStream.java:1508)
> at
> java.io.ObjectOutputStream.writeOrdinaryObject(ObjectOutputStream.java:1431)
> at java.io.ObjectOutputStream.writeObject0(ObjectOutputStream.java:1177)
> at java.io.ObjectOutputStream.writeObject(ObjectOutputStream.java:347)
> at
> org.apache.spark.serializer.JavaSerializationStream.writeObject(JavaSerializer.scala:42)
> at
> org.apache.spark.serializer.JavaSerializerInstance.serialize(JavaSerializer.scala:73)
> at
> org.apache.spark.util.ClosureCleaner$.ensureSerializable(ClosureCleaner.scala:164)
> This seems to be due to WrapAsJava.scala being non serializable
> ../..
> implicit def mapAsJavaMap[A, B](m: Map[A, B]): ju.Map[A, B] = m match {
> //case JConcurrentMapWrapper(wrapped) => wrapped
> case JMapWrapper(wrapped) => wrapped.asInstanceOf[ju.Map[A, B]]
> case _ => new MapWrapper(m)
> }
> ../..
> The workaround is to manually wrapper this map into another one (serialized)
> Map<String, String> map = myJavaRDD.collectAsMap();
> Map<String, String> tmp = new HashMap<String, String>(map);
> myOtherJavaRDD.mapToPair(new CustomFunction(tmp))
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