Github user andrewor14 commented on a diff in the pull request:
https://github.com/apache/spark/pull/3347#discussion_r32789943
--- Diff:
examples/src/main/scala/org/apache/spark/examples/DFSReadWriteTest.scala ---
@@ -0,0 +1,136 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements. See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License. You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.spark.examples
+
+import java.io.File
+import scala.io.Source._
+import org.apache.spark.{SparkContext, SparkConf}
+import org.apache.spark.SparkContext._
+
+/**
+ * Simple test for reading and writing to a distributed
+ * file system. This example does the following:
+ *
+ * 1. Reads local file
+ * 2. Computes word count on local file
+ * 3. Writes local file to a DFS
+ * 4. Reads the file back from the DFS
+ * 5. Computes word count on the file using Spark
+ * 6. Compares the word count results
+ */
+object DFSReadWriteTest {
+
+ private var localFilePath: File = new File(".")
+ private var dfsDirPath: String = ""
+
+ private val NPARAMS = 2
+
+ private def readFile(filename: String): List[String] = {
+ val lineIter: Iterator[String] = fromFile(filename).getLines()
+ val lineList: List[String] = lineIter.toList
+ lineList
+ }
+
+ private def printUsage() {
+ val usage: String = "DFS Read-Write Test\n" +
+ "\n" +
+ "Usage: localFile dfsDir\n" +
+ "\n" +
+ "localFile - (string) local file to use in test\n" +
+ "dfsDir - (string) DFS directory for read/write tests\n"
+
+ println(usage)
+ }
+
+ private def parseArgs(args: Array[String]) {
+ if(args.length != NPARAMS) {
+ printUsage()
+ System.exit(1)
+ }
+
+ var i = 0
+
+ localFilePath = new File(args(i))
+ if(!localFilePath.exists) {
+ System.err.println("Given path (" + args(i) + ") does not exist.\n")
+ printUsage()
+ System.exit(1)
+ }
+
+ if(!localFilePath.isFile) {
+ System.err.println("Given path (" + args(i) + ") is not a file.\n")
+ printUsage()
+ System.exit(1)
+ }
+
+ i += 1
+ dfsDirPath = args(i)
+ }
+
+ def runLocalWordCount(fileContents: List[String]): Int = {
+ fileContents.flatMap(_.split(" "))
+ .flatMap(_.split("\t"))
+ .filter(_.size > 0)
+ .groupBy(w => w)
+ .mapValues(_.size)
+ .values
+ .sum
+ }
+
+ def main(args: Array[String]) {
+ parseArgs(args)
+
+ println("Performing local word count")
+ val fileContents = readFile(localFilePath.toString())
+ val localWordCount = runLocalWordCount(fileContents)
+
+ println("Creating SparkConf")
+ val conf = new SparkConf().setAppName("DFS Read Write Test")
+
+ println("Creating SparkContext")
+ val sc = new SparkContext(conf)
+
+ println("Writing local file to DFS")
+ val dfsFilename = dfsDirPath + "/dfs_read_write_test"
+ val fileRDD = sc.parallelize(fileContents)
+ fileRDD.saveAsTextFile(dfsFilename)
+
+ println("Reading file from DFS and running Word Count")
+ val readFileRDD = sc.textFile(dfsFilename)
+
+ val dfsWordCount = readFileRDD
+ .flatMap(_.split(" "))
+ .flatMap(_.split("\t"))
+ .filter(_.size > 0)
+ .map(w => (w, 1))
+ .countByKey()
+ .values
+ .sum
+
+ sc.stop()
+
+ if(localWordCount == dfsWordCount) {
--- End diff --
style: space after `if`
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