编程那点事
spark streaming可以从任何数据源来接收数据，哪怕是除了它内置支持的数据源以外的其他数据源（比如flume、kafka、socket等）。
如果我们想要从spark streaming没有内置支持的数据源中接收实时数据，那么我们需要自己实现一个receiver。
实现一个自定义的receiver
一个自定义的receiver必须实现以下两个方法：onStart()、onStop()。onStart()和onStop()方法必须不能阻塞数据，一般来说，
onStart()方法会启动负责接收数据的线程，onStop()方法会确保之前启动的线程都已经停止了。负责接收数据的线程可以调用isStopped()方法来检查它们是否应该停止接收数据。
一旦数据被接收了，就可以调用store(data)方法，数据就可以被存储在Spark内部。有一系列的store()重载方法供我们调用，来将数据每次一条进行存储，或是每次存储一个集合或序列化的数据。
接收线程中的任何异常都应该被捕获以及正确处理，从而避免receiver的静默失败。restart()方法会通过异步地调用onStop()和onStart()方法来重启receiver。stop()方法会调用onStop()方法来停止receiver。reportError()方法会汇报一个错误消息给driver，但是不停止或重启receiver。
package cn.spark.study.streaming.upgrade;
import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.net.ConnectException;
import java.net.Socket;
import org.apache.spark.storage.StorageLevel;
import org.apache.spark.streaming.receiver.Receiver;
public class JavaCustomReceiver extends Receiver<String> {
private static final long serialVersionUID = 3184893502610667539L;
String host = null;
int port = -1;
public JavaCustomReceiver(String host_ , int port_) {
super(StorageLevel.MEMORY_AND_DISK_2());
host = host_;
port = port_;
}
public void onStart() {
// Start the thread that receives data over a connection
new Thread() {
@Override public void run() {
receive();
}
}.start();
}
public void onStop() {
}
/** Create a socket connection and receive data until receiver is stopped */
private void receive() {
Socket socket = null;
String userInput = null;
try {
// connect to the server
socket = new Socket(host, port);
BufferedReader reader = new BufferedReader(new InputStreamReader(socket.getInputStream()));
// Until stopped or connection broken continue reading
while (!isStopped() && (userInput = reader.readLine()) != null) {
System.out.println("Received data '" + userInput + "'");
store(userInput);
}
reader.close();
socket.close();
// Restart in an attempt to connect again when server is active again
restart("Trying to connect again");
} catch(ConnectException ce) {
// restart if could not connect to server
restart("Could not connect", ce);
} catch(Throwable t) {
// restart if there is any other error
restart("Error receiving data", t);
}
}
}在spark streaming中使用自定义的receiver
JavaDStream<String> lines = jssc.receiverStream(new JavaCustomReceiver(host, port));
Java代码
package cn.spark.study.streaming.upgrade;
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;
public class CustomReceiverWordCount {
public static void main(String[] args) throws Exception {
SparkConf conf = new SparkConf()
.setMaster("local[2]")
.setAppName("wordcount");
JavaStreamingContext jssc = new JavaStreamingContext(conf, Durations.seconds(1));
JavaDStream<String> lines = jssc.receiverStream(new JavaCustomReceiver("localhost", 9999));
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 {
// TODO Auto-generated method stub
return v1 + v2;
}
});
wordCounts.print();
jssc.start();
jssc.awaitTermination();
jssc.close();
}
}安装网络服务工具
wget http://vault.centos.org/6.3/os/i386/Packages/nc-1.84-22.el6.i686.rpm rpm -iUv nc-1.84-22.el6.i686.rpm nc -lk 9999
