解决 SparkException: Task not serializable when importing PMML model

Question

我想导入 PMML 模型，以使用 Spark 计算分数。当我不使用 spark 时一切正常，但我不能在映射器中使用我的方法。

问题是我需要一个来自 org.jpmml.evaluator.Evaluator 的 Evaluation 对象，它似乎不是可序列化的。所以我尝试使用以下 class :

使其成为 Serialiazable

package util;

import java.io.IOException;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.io.Serializable;

import org.jpmml.evaluator.Evaluator;

public class SerializableEvaluator implements Serializable {

    private static final long serialVersionUID = 6631604036553063657L;
    private Evaluator evaluator;

    public SerializableEvaluator(Evaluator evaluator) {
        this.evaluator = evaluator;
    }

    public Evaluator getEvaluator() {
        return evaluator;
    }

    private void writeObject(ObjectOutputStream out) throws IOException {
        out.writeObject(evaluator);
    }

    private void readObject(ObjectInputStream in) throws IOException, ClassNotFoundException {
        Evaluator eval = (Evaluator) in.readObject();
    }
}

我还使我所有的 classes 都可以序列化。

这是我的代码示例：

        logger.info("Print 5 first rows----------------------------");
        strTitanicRDD
                .take(5)
                .forEach(row -> logger.info(row));
        logger.info("Print 5 first Titatnic Obs---------------------");
        strTitanicRDD
                .map(row -> new TitanicObservation(row))
                .take(5)
                .forEach(titanic -> logger.info(titanic.toString()));
        logger.info("Print 5 first Scored Titatnic Obs---------------");

        try{strTitanicRDD
            .map(row -> new TitanicObservation(row))
            .map(
                new Function<TitanicObservation,String>(){

                    private static final long serialVersionUID = -2968122030659306400L;

                    @Override
                    public String call(TitanicObservation titanic) throws Exception {
                        String res = PmmlUtil.computeScoreTitanic(evaluator, titanic);
                        return res;
                    }

                })
        .take(5)
        .forEach(row -> logger.info(row));

但我认为我的代码不会帮助您解决我的问题，这很清楚（请参阅日志:)

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:1623) at org.apache.spark.rdd.RDD.map(RDD.scala:286) at org.apache.spark.api.java.JavaRDDLike$class.map(JavaRDDLike.scala:89) at org.apache.spark.api.java.AbstractJavaRDDLike.map(JavaRDDLike.scala:46) at score.acv.AppWithSpark.main(AppWithSpark.java:117) at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) at java.lang.reflect.Method.invoke(Method.java:497) at org.apache.spark.deploy.SparkSubmit$.org$apache$spark$deploy$SparkSubmit$$runMain(SparkSubmit.scala:577) at org.apache.spark.deploy.SparkSubmit$.doRunMain(SparkSubmit.scala:174) at org.apache.spark.deploy.SparkSubmit$.submit(SparkSubmit.scala:197) at org.apache.spark.deploy.SparkSubmit$.main(SparkSubmit.scala:112) at org.apache.spark.deploy.SparkSubmit.main(SparkSubmit.scala)

Caused by: java.io.NotSerializableException: org.xml.sax.helpers.LocatorImpl Serialization stack:
    at org.apache.spark.serializer.SerializationDebugger$.improveException(SerializationDebugger.scala:38)
    at org.apache.spark.serializer.JavaSerializationStream.writeObject(JavaSerializer.scala:47)
    at org.apache.spark.serializer.JavaSerializerInstance.serialize(JavaSerializer.scala:80)
    at org.apache.spark.util.ClosureCleaner$.ensureSerializable(ClosureCleaner.scala:164)
    ... 15 more

Answer 1

在 org.jpmml.evaluator.Evaluator 接口后面有一些 org.jpmml.evaluator.ModelEvaluator subclass 的实例。 class ModelEvaluator 及其所有子 class 都是按设计可序列化的。问题与您在开始时提供给 ModelEvaluatorFactory#newModelManager(PMML) 方法的 org.dmg.pmml.PMML 对象实例有关。

简而言之，每个 PMML class 模型对象都可以附加 SAX 定位器信息。这在开发和测试阶段非常有用，可用于查找有问题的 XML 内容。但是，在生产阶段，不应再保留此信息。您可以通过正确配置 JAXB 运行时来禁用 SAX 定位器信息，或者通过使用 null 参数调用 PMMLObject#setLocator(Locatable) 来简单地清除现有的 SAX 定位器实例。后者的功能由 org.jpmml.model.visitors.LocatorNullifier 访问者 class 正式化。

完整示例，请参阅官方JPMML-Spark project的org.jpmml.spark.EvaluatorUtil实用程序class（尤其是第73至75行）。为什么不首先使用 JPMML-Spark？

解决 SparkException: Task not serializable when importing PMML model

Resolve SparkException: Task not serializable when importing PMML model

java

serialization

pmml

apache-spark