输入DStream之基础数据源
HDFS文件
基于HDFS文件的实时计算,其实就是,监控一个HDFS目录,只要其中有新文件出现,就实时处理。相当于处理实时的文件流。
streamingContext.fileStream<KeyClass, ValueClass, InputFormatClass>(dataDirectory)
streamingContext.fileStream[KeyClass, ValueClass, InputFormatClass](dataDirectory)
Spark Streaming会监视指定的HDFS目录,并且处理出现在目录中的文件。要注意的是,所有放入HDFS目录中的文件,都必须有相同的格式;必须使用移动或者重命名的方式,将文件移入目录;一旦处理之后,文件的内容即使改变,也不会再处理了;基于HDFS文件的数据源是没有Receiver的,因此不会占用一个cpu core。
java版本
package cn.spark.study.streaming;
import java.util.Arrays;
import org.apache.spark.SparkConf;
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 org.apache.spark.streaming.Durations;
import org.apache.spark.streaming.api.java.JavaDStream;
import org.apache.spark.streaming.api.java.JavaPairDStream;
import org.apache.spark.streaming.api.java.JavaStreamingContext;
import scala.Tuple2;
/**
* 基于HDFS文件的实时wordcount程序
* @author Administrator
*
*/
public class HDFSWordCount {
public static void main(String[] args) {
SparkConf conf = new SparkConf()
.setMaster("local[2]")
.setAppName("HDFSWordCount");
JavaStreamingContext jssc = new JavaStreamingContext(conf, Durations.seconds(5));
// 首先,使用JavaStreamingContext的textFileStream()方法,针对HDFS目录创建输入数据流
JavaDStream<String> lines = jssc.textFileStream("hdfs://spark1:9000/wordcount_dir");
// 执行wordcount操作
JavaDStream<String> words = lines.flatMap(new FlatMapFunction<String, String>() {
private static final long serialVersionUID = 1L;
@Override
public Iterable<String> call(String line) throws Exception {
return Arrays.asList(line.split(" "));
}
});
JavaPairDStream<String, Integer> pairs = words.mapToPair(
new PairFunction<String, String, Integer>() {
private static final long serialVersionUID = 1L;
@Override
public Tuple2<String, Integer> call(String word)
throws Exception {
return new Tuple2<String, Integer>(word, 1);
}
});
JavaPairDStream<String, Integer> wordCounts = pairs.reduceByKey(
new Function2<Integer, Integer, Integer>() {
private static final long serialVersionUID = 1L;
@Override
public Integer call(Integer v1, Integer v2) throws Exception {
return v1 + v2;
}
});
wordCounts.print();
jssc.start();
jssc.awaitTermination();
jssc.close();
}
}
scala版本
package cn.spark.study.streaming
import org.apache.spark.SparkConf
import org.apache.spark.streaming.StreamingContext
import org.apache.spark.streaming.Seconds
/**
* @author Administrator
*/
object HDFSWordCount {
def main(args: Array[String]): Unit = {
val conf = new SparkConf()
.setMaster("local[2]")
.setAppName("HDFSWordCount")
val ssc = new StreamingContext(conf, Seconds(5))
val lines = ssc.textFileStream("hdfs://spark1:9000/wordcount_dir")
val words = lines.flatMap { _.split(" ") }
val pairs = words.map { word => (word, 1) }
val wordCounts = pairs.reduceByKey(_ + _)
wordCounts.print()
ssc.start()
ssc.awaitTermination()
}
}
运行步骤:
打包,上传到linux中;编写spark-submit脚本;运行脚本;上传文件到hdfs://spark1:9000/wordcount_dir/下。
hadoop fs -put t1.txt /wordcount_dir/tt1.txt
运行结果: