Custom Receiver that receives data over a socket from apache spark

Description

Demo Code

/*//from w  w w .  j  a  va  2  s. co  m
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *    http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.apache.spark.examples.streaming;

import com.google.common.collect.Lists;

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.storage.StorageLevel;
import org.apache.spark.streaming.Duration;
import org.apache.spark.streaming.api.java.JavaDStream;
import org.apache.spark.streaming.api.java.JavaPairDStream;
import org.apache.spark.streaming.api.java.JavaReceiverInputDStream;
import org.apache.spark.streaming.api.java.JavaStreamingContext;
import org.apache.spark.streaming.receiver.Receiver;
import scala.Tuple2;

import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.net.ConnectException;
import java.net.Socket;
import java.util.regex.Pattern;

/**
 * Custom Receiver that receives data over a socket. Received bytes is interpreted as
 * text and \n delimited lines are considered as records. They are then counted and printed.
 *
 * Usage: JavaCustomReceiver <master> <hostname> <port>
 *   <master> is the Spark master URL. In local mode, <master> should be 'local[n]' with n > 1.
 *   <hostname> and <port> of the TCP server that Spark Streaming would connect to receive data.
 *
 * To run this on your local machine, you need to first run a Netcat server
 *    `$ nc -lk 9999`
 * and then run the example
 *    `$ bin/run-example org.apache.spark.examples.streaming.JavaCustomReceiver localhost 9999`
 */

public class JavaCustomReceiver extends Receiver<String> {
    private static final Pattern SPACE = Pattern.compile(" ");

    public static void main(String[] args) {
        if (args.length < 2) {
            System.err
                    .println("Usage: JavaCustomReceiver <hostname> <port>");
            System.exit(1);
        }

        StreamingExamples.setStreamingLogLevels();

        // Create the context with a 1 second batch size
        SparkConf sparkConf = new SparkConf()
                .setAppName("JavaCustomReceiver");
        JavaStreamingContext ssc = new JavaStreamingContext(sparkConf,
                new Duration(1000));

        // Create a input stream with the custom receiver on target ip:port and count the
        // words in input stream of \n delimited text (eg. generated by 'nc')
        JavaReceiverInputDStream<String> lines = ssc
                .receiverStream(new JavaCustomReceiver(args[0], Integer
                        .parseInt(args[1])));
        JavaDStream<String> words = lines
                .flatMap(new FlatMapFunction<String, String>() {
                    @Override
                    public Iterable<String> call(String x) {
                        return Lists.newArrayList(SPACE.split(x));
                    }
                });
        JavaPairDStream<String, Integer> wordCounts = words.mapToPair(
                new PairFunction<String, String, Integer>() {
                    @Override
                    public Tuple2<String, Integer> call(String s) {
                        return new Tuple2<String, Integer>(s, 1);
                    }
                }).reduceByKey(new Function2<Integer, Integer, Integer>() {
            @Override
            public Integer call(Integer i1, Integer i2) {
                return i1 + i2;
            }
        });

        wordCounts.print();
        ssc.start();
        ssc.awaitTermination();
    }

    // ============= Receiver code that receives data over a socket ==============

    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() {
        // There is nothing much to do as the thread calling receive()
        // is designed to stop by itself isStopped() returns false
    }

    /** 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("Error receiving data", t);
        }
    }
}
Custom Receiver that receives data over a socket from apache spark - Java Big Data

Description

Demo Code

Related Tutorials
