java
1 /**
2 * accumulator可以让多个task共同操作一份变量,主要进行多个节点对一个变量进行共享性的操作,accumulator只提供了累加的功能
3 * 只有driver可以获取accumulator的值
4 * @author Tele
5 */
6 public class AccumulatorDemo {
7 private static SparkConf conf = new SparkConf().setMaster("local").setAppName("AccumulatorDemo");
8 private static JavaSparkContext jsc = new JavaSparkContext(conf);
9
10 public static void main(String[] args) {
11 List<Integer> list = Arrays.asList(1, 2, 3, 4, 5, 6);
12
13 JavaRDD<Integer> rdd = jsc.parallelize(list);
14
15 /*
16 * Accumulator<Integer> accumulator = jsc.accumulator(10);
17 *
18 * rdd.foreach(new VoidFunction<Integer>() {
19 *
20 * private static final long serialVersionUID = 1L;
21 *
22 * @Override public void call(Integer t) throws Exception { accumulator.add(t);
23 * } }); System.out.println(accumulator.value());
24 */
25
26 LongAccumulator la = new LongAccumulator();
27 la.setValue(100L);
28
29 jsc.sc().register(la, "数值累加器");
30
31 rdd.foreach(new VoidFunction<Integer>() {
32
33 private static final long serialVersionUID = 1L;
34
35 @Override
36 public void call(Integer t) throws Exception {
37 // 不能在算子内部获得accumulator.value()
38 la.add(t);
39 }
40 });
41
42 System.out.println(la.value());
43 jsc.close();
44 }
45 }
scala
1 object AccumulatorDemo {
2 def main(args: Array[String]): Unit = {
3 val conf = new SparkConf().setMaster("local").setAppName("accumulator");
4 val sc = new SparkContext(conf);
5
6 val arr = Array(1, 2, 3, 4, 5);
7 val rdd = sc.parallelize(arr, 1);
8
9 val accumulator = new LongAccumulator;
10 accumulator.add(100);
11
12 sc.register(accumulator);
13
14 rdd.foreach(accumulator.add(_));
15
16 println(accumulator.value);
17
18 }
19 }