Spark wordcount - Python, Scala, Java

基於Spark實現的Python, Scala, Java三個版本的、經典的分佈式單詞計數代碼。

1. Scala

val input = sc.textFile("hdfs://...")
val words = input.flatMap(x => x.split(" "))
val result = words.map(x => (x, 1)).reduceByKey((x, y) => x + y).persist()

println(result.collect().mkString("\n"))  //collect()在數據量比較小、單機內存能裝載下時可以使用

2.Python

rdd = sc.textFile("s3://...")
words = rdd.flatMap(lambda x: x.split(" "))
result = words.map(lambda x: (x, 1)).reduceByKey(lambda x, y: x + y)

3.Java

JavaRDD<String> input = sc.textFile("s3://...")
JavaRDD<String> words = rdd.flatMap(new FlatMapFunction<String, String>() {
public Iterable<String> call(String x) { return Arrays.asList(x.split(" ")); }
});
JavaPairRDD<String, Integer> result = words.mapToPair(
new PairFunction<String, String, Integer>() {
public Tuple2<String, Integer> call(String x) { return new Tuple2(x, 1); }
}).reduceByKey(
new Function2<Integer, Integer, Integer>() {
public Integer call(Integer a, Integer b) { return a + b; }
});