Spark任務序列化和關閉

當傳遞給Spark RDD操作的lambda引用其範圍之外的對象時，它將包含創建分佈式執行的序列化任務所需的上下文。在下面的簡單例子中，爲什麼它決定序列化整個OutClass實例，而不是乘法器？我懷疑乘數實際上是引擎蓋下的一個Scala吸氣器方法，因此它必須包含該類的參考。聲明OuterClass extends Serializable是可行的，但它會引入不必要的約束。我真的很感激一種方法來使它在沒有聲明OuterClass可序列化的情況下工作。Spark任務序列化和關閉

object ClosureTest { 
    def main(args: Array[String]): Unit = { 
    val sc = SparkContext.getOrCreate(new SparkConf().setMaster("local[2]").setAppName("test")) 
    println(new OuterClass(10).sparkSumProd(sc.parallelize(Seq(1,2,3)))) 
    } 
    class OuterClass(multiplier: Int) { 
    def sparkSumProd(data: RDD[Int]): Double = { 
     data.map{ 
     v => v * multiplier 
     }.sum() 
    } 
    } 
}

下面是星火的SerializationDebugger

Exception in thread "main" org.apache.spark.SparkException: Task not serializable 
    at org.apache.spark.util.ClosureCleaner$.ensureSerializable(ClosureCleaner.scala:298) 
    at org.apache.spark.util.ClosureCleaner$.org$apache$spark$util$ClosureCleaner$$clean(ClosureCleaner.scala:288) 
    at org.apache.spark.util.ClosureCleaner$.clean(ClosureCleaner.scala:108) 
    at org.apache.spark.SparkContext.clean(SparkContext.scala:2056) 
    at org.apache.spark.rdd.RDD$$anonfun$map$1.apply(RDD.scala:366) 
    at org.apache.spark.rdd.RDD$$anonfun$map$1.apply(RDD.scala:365) 
    at org.apache.spark.rdd.RDDOperationScope$.withScope(RDDOperationScope.scala:151) 
    at org.apache.spark.rdd.RDDOperationScope$.withScope(RDDOperationScope.scala:112) 
    at org.apache.spark.rdd.RDD.withScope(RDD.scala:358) 
    at org.apache.spark.rdd.RDD.map(RDD.scala:365) 
    at ClosureTest$OuterClass.sparkSumProd(ClosureTest.scala:14) 
    at ClosureTest$.main(ClosureTest.scala:10) 
    at ClosureTest.main(ClosureTest.scala) 
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) 
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) 
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) 
    at java.lang.reflect.Method.invoke(Method.java:498) 
    at com.intellij.rt.execution.application.AppMain.main(AppMain.java:147) 
Caused by: java.io.NotSerializableException: ClosureTest$OuterClass 
Serialization stack: 
    - object not serializable (class: ClosureTest$OuterClass, value: [email protected]) 
    - field (class: ClosureTest$OuterClass$$anonfun$sparkSumProd$1, name: $outer, type: class ClosureTest$OuterClass) 
    - object (class ClosureTest$OuterClass$$anonfun$sparkSumProd$1, <function1>) 
    at org.apache.spark.serializer.SerializationDebugger$.improveException(SerializationDebugger.scala:40) 
    at org.apache.spark.serializer.JavaSerializationStream.writeObject(JavaSerializer.scala:46) 
    at org.apache.spark.serializer.JavaSerializerInstance.serialize(JavaSerializer.scala:100) 
    at org.apache.spark.util.ClosureCleaner$.ensureSerializable(ClosureCleaner.scala:295) 
    ... 17 more

來源

2016-12-04 gerry

輸出只需指定類級別變量，局部變量也可以正常工作。

object ClosureTest { 
    def main(args: Array[String]): Unit = { 
    val sc = SparkContext.getOrCreate(new SparkConf().setMaster("local[2]").setAppName("test")) 
    println(new OuterClass(10).sparkSumProd(sc.parallelize(Seq(1,2,3)))) 
    } 
    class OuterClass(multiplier: Int) { 
    def sparkSumProd(data: RDD[Int]): Double = { 
     val m = multiplier 
     data.map{ 
     v => v * m 
     }.sum() 
    } 
    } 
}

來源

2016-12-04 01:41:13 gerry

Spark任務序列化和關閉

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