Quickstart

$ cd ~/Downloads        # Go to download directory
$ tar xzf flink-*.tgz   # Unpack the downloaded archive
$ cd flink-1.5.1

object SocketWindowWordCount {

  def main(args: Array[String]) : Unit = {

    // the host and the port to connect to
    var hostname: String = "localhost"
    var port: Int = 0

    try {
      val params = ParameterTool.fromArgs(args)
      hostname = if (params.has("hostname")) params.get("hostname") else "localhost"
      port = params.getInt("port")
    } catch {
      case e: Exception => {
        System.err.println("No port specified. Please run 'SocketWindowWordCount " +
          "--hostname <hostname> --port <port>', where hostname (localhost by default) and port " +
          "is the address of the text server")
        System.err.println("To start a simple text server, run 'netcat -l <port>' " +
          "and type the input text into the command line")
        return
      }
    }
    
    // get the execution environment
    val env: StreamExecutionEnvironment = StreamExecutionEnvironment.getExecutionEnvironment
    
    // get input data by connecting to the socket
    val text: DataStream[String] = env.socketTextStream(hostname, port, '\n')

    // parse the data, group it, window it, and aggregate the counts 
    val windowCounts = text
          .flatMap { w => w.split("\\s") }
          .map { w => WordWithCount(w, 1) }
          .keyBy("word")
          .timeWindow(Time.seconds(5))
          .sum("count")

    // print the results with a single thread, rather than in parallel
    windowCounts.print().setParallelism(1)

    env.execute("Socket Window WordCount")
  }

  /** Data type for words with count */
  case class WordWithCount(word: String, count: Long)
}

public class SocketWindowWordCount {

	public static void main(String[] args) throws Exception {

		// the host and the port to connect to
		final String hostname;
		final int port;
		try {
			final ParameterTool params = ParameterTool.fromArgs(args);
			hostname = params.has("hostname") ? params.get("hostname") : "localhost";
			port = params.getInt("port");
		} catch (Exception e) {
			System.err.println("No port specified. Please run 'SocketWindowWordCount " +
				"--hostname <hostname> --port <port>', where hostname (localhost by default) " +
				"and port is the address of the text server");
			System.err.println("To start a simple text server, run 'netcat -l <port>' and " +
				"type the input text into the command line");
			return;
		}

		// get the execution environment
		final StreamExecutionEnvironment env = StreamExecutionEnvironment.getExecutionEnvironment();

		// get input data by connecting to the socket
		DataStream<String> text = env.socketTextStream(hostname, port, "\n");

		// parse the data, group it, window it, and aggregate the counts
		DataStream<WordWithCount> windowCounts = text

			.flatMap(new FlatMapFunction<String, WordWithCount>() {
				@Override
				public void flatMap(String value, Collector<WordWithCount> out) {
					for (String word : value.split("\\s")) {
						out.collect(new WordWithCount(word, 1L));
					}
				}
			})

			.keyBy("word")
			.timeWindow(Time.seconds(5))

			.reduce(new ReduceFunction<WordWithCount>() {
				@Override
				public WordWithCount reduce(WordWithCount a, WordWithCount b) {
					return new WordWithCount(a.word, a.count + b.count);
				}
			});

		// print the results with a single thread, rather than in parallel
		windowCounts.print().setParallelism(1);

		env.execute("Socket Window WordCount");
	}

	// ------------------------------------------------------------------------

	/**
	 * Data type for words with count.
	 */
	public static class WordWithCount {

		public String word;
		public long count;

		public WordWithCount() {}

		public WordWithCount(String word, long count) {
			this.word = word;
			this.count = count;
		}

		@Override
		public String toString() {
			return word + " : " + count;
		}
	}
}