Spark平臺上的JavaWordCount示例

WorldCount目錄結構如下：

[root@master WordCount]# find .
.
./src
./src/main
./src/main/java
./src/main/java/JavaWordCount.java
./pom.xml

其中./pom.xml內容如下：
（注意對應以後生成的jar包，本例中最後生成word-count-1.0.jar）

<project>
  <groupId>edu.berkeley</groupId>
  <artifactId>word-count</artifactId>
  <modelVersion>4.0.0</modelVersion>
  <name>JavaWordCount</name>
  <packaging>jar</packaging>
  <version>1.0</version>
  <dependencies>
    <dependency> <!-- Spark dependency -->
      <groupId>org.apache.spark</groupId>
      <artifactId>spark-core_2.10</artifactId>
      <version>1.2.0</version>
    </dependency>
    <dependency> <!-- Hadoop dependency -->
      <groupId>org.apache.hadoop</groupId>
      <artifactId>hadoop-client</artifactId>
      <version>2.6.0</version>
    </dependency>
  </dependencies>
</project>

./src/main/java/JavaWordCount.java內容如下：

import scala.Tuple2;
import org.apache.spark.SparkConf;
import org.apache.spark.api.java.JavaPairRDD;
import org.apache.spark.api.java.JavaRDD;
import org.apache.spark.api.java.JavaSparkContext;
import org.apache.spark.api.java.function.FlatMapFunction;
import org.apache.spark.api.java.function.Function2;
import org.apache.spark.api.java.function.PairFunction;
import java.util.Arrays;
import java.util.List;
import java.util.regex.Pattern;

public final class JavaWordCount {
  private static final Pattern SPACE = Pattern.compile(" ");
  public static void main(String[] args) throws Exception {
    if (args.length < 1) {
      System.err.println("Usage: JavaWordCount <file>");
      System.exit(1);
    }

    SparkConf sparkConf = new SparkConf().setAppName("JavaWordCount");
    JavaSparkContext ctx = new JavaSparkContext(sparkConf);
    JavaRDD<String> lines = ctx.textFile(args[0], 1);

    JavaRDD<String> words = lines.flatMap(new FlatMapFunction<String, String>() {
      @Override
      public Iterable<String> call(String s) {
        return Arrays.asList(SPACE.split(s));
      }
    });

    JavaPairRDD<String, Integer> ones = words.mapToPair(new PairFunction<String, String, Integer>() {
      @Override
      public Tuple2<String, Integer> call(String s) {
        return new Tuple2<String, Integer>(s, 1);
      }
    });

    JavaPairRDD<String, Integer> counts = ones.reduceByKey(new Function2<Integer, Integer, Integer>() {
      @Override
      public Integer call(Integer i1, Integer i2) {
        return i1 + i2;
      }
    });

    List<Tuple2<String, Integer>> output = counts.collect();
    for (Tuple2<?,?> tuple : output) {
      System.out.println(tuple._1() + ": " + tuple._2());
    }
    ctx.stop();
  }
}

進入WorldCount目錄，並編譯程序並打包：

[root@master WordCount]# mvn package

然後往集羣上發佈：

[root@master WordCount]#spark-submit \
  --class JavaWordCount \
  --master yarn-cluster \
  --num-executors 2 \
  --executor-memory 6g \
  --executor-cores 4  \
  target/word-count-1.0.jar \
  /user/root/random0.data

若–master 後用的是yarn-cluster，則在log日誌中（從WebUI進入）查看結果

package: 1
For: 2
processing.: 1
Programs: 1
Because: 1
The: 1
cluster.: 1
its: 1
……

若–master 後用的是yarn-client，則在控制檯查看結果