Antoine Amend created SPARK-3926:
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Summary: 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: 1.1.0
Environment: CentOS / Spark 1.1 / Hadoop Hortonworks 2.4.0.2.1.2.0-402
Reporter: Antoine Amend
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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