scala - Spark 提交错误 : Cannot load main class from JAR file

Question

我正在尝试在 Scala 集群模式下spark-submit 一个应用程序。它在 PySpark 中运行良好，但在尝试使用 Scala 运行时弹出上述错误。如果我必须添加 SBT 和 Maven 依赖项，您能否详细说明该过程(我无法在 Google 中找到)

这是我的代码:

import org.apache.spark.SparkContext
import org.apache.spark.SparkContext._
import org.apache.spark.SparkConf

object MyFirst {
  def main(args: Array[String]) {
    // create Spark context with Spark configuration
    val sc = new SparkContext(new SparkConf().setAppName("Spark Count"))

    // get threshold
    val threshold = args(1).toInt

    // read in text file and split each document into words
    val tokenized = sc.textFile(args(0)).flatMap(_.split(" "))

    // count the occurrence of each word
    val wordCounts = tokenized.map((_, 1)).reduceByKey(_ + _)

    // filter out words with fewer than threshold occurrences
    val filtered = wordCounts.filter(_._2 >= threshold)

    // count characters
    val charCounts = filtered.flatMap(_._1.toCharArray).map((_, 1)).reduceByKey(_ + _)

    System.out.println(charCounts.collect().mkString(", "))
  }
}

这是我的 Build.sbt

name := "MyFirst"

scalaVersion := "2.10.3"

// https://mvnrepository.com/artifact/org.apache.spark/spark-core
libraryDependencies += "org.apache.spark" %% "spark-core" % "2.2.0"

我的 Spark 提交是:spark-submit MyFirst --class MyFirst/home/ram/Downloads/sbt/src/target/scala-2.10/MyFirst_2.10-0.1.0-SNAPSHOT。 jar

Answer 1

我以前遇到过这个问题。

尝试为您的类定义一个包，如下所示:

package com.testing

import org.apache.spark.SparkContext
import org.apache.spark.SparkContext._
import org.apache.spark.SparkConf

object MyFirst {
  def main(args: Array[String]) {
    // create Spark context with Spark configuration
    val sc = new SparkContext(new SparkConf().setAppName("Spark Count"))
    // more code ...
  }
}

然后使用:

spark-submit MyFirst --class com.testing.MyFirst /home/ram/Downloads/sbt/src/target/scala-2.10/MyFirst_2.10-0.1.0-SNAPSHOT.jar

还要确保您已经创建了 MANIFEST.MF文件。

这是一个简短的示例:

Manifest-Version: 1.0
Main-Class: com.testing.MyFirst