如何从cloudera单节点集群的spark-shell中的hdfs访问文件

Question

尝试在面临问题的Cloudera群集上从spark-shell创建RDD，同时从hdfs位置访问文件：

scala> val file = sc.textFile("hdfs://user/cloudera/nvegesn/emp.txt")
<console>:13: error: not found: value sc

Answer 1

你忘了定义Spark Context。

val conf = new SparkConf().setAppName("Simple Application")
val sc = new SparkContext(conf)

例如：

/* SimpleApp.scala */
import org.apache.spark.SparkContext
import org.apache.spark.SparkContext._
import org.apache.spark.SparkConf

object SimpleApp {
  def main(args: Array[String]) {
    val logFile = "hdfs://user/cloudera/nvegesn/emp.txt"
    val conf = new SparkConf().setAppName("Simple Application")
    val sc = new SparkContext(conf)
    val logData = sc.textFile(logFile, 2).cache()
    val numAs = logData.filter(line => line.contains("a")).count()
    val numBs = logData.filter(line => line.contains("b")).count()
    println("Lines with a: %s, Lines with b: %s".format(numAs, numBs))
  }
}