you are using a BoundedOutOfOrdernessTimestampExtractor to generate watermarks.
The BoundedOutOfOrdernessTimestampExtractor is a periodic watermark assigner and only generates watermarks if a watermark interval is configured.
Without watermarks, the query cannot "make progress" and only computes its result when the program is closed (sources emit a MAX_LONG watermark when being canceled).

Long story short: you need to configure the watermark interval: env.getConfig.setAutoWatermarkInterval(100L);

Best, Fabian

2017-12-14 16:30 GMT+01:00 Plamen Paskov <plamen.paskov@next-stream.com>:


I'm trying to run the following streaming program in my local flink 1.3.2 environment. The program compile and run without any errors but the print() call doesn't display anything. Once i stop the program i receive all aggregated data. Any ideas how to make it output regularly or when new data come/old data updated?

package flink;

import org.apache.flink.api.common.functions.MapFunction;
import org.apache.flink.api.java.tuple.Tuple2;
import org.apache.flink.streaming.api.TimeCharacteristic;
import org.apache.flink.streaming.api.datastream.DataStream;
import org.apache.flink.streaming.api.datastream.SingleOutputStreamOperator;
import org.apache.flink.streaming.api.environment.StreamExecutionEnvironment;
import org.apache.flink.streaming.api.functions.timestamps.BoundedOutOfOrdernessTimestampExtractor;
import org.apache.flink.streaming.api.windowing.time.Time;
import org.apache.flink.table.api.Table;
import org.apache.flink.table.api.java.Slide;
import org.apache.flink.table.api.java.StreamTableEnvironment;

import java.sql.Timestamp;

public class StreamingJob {
    public static void main(String[] args) throws Exception {
        StreamExecutionEnvironment env = StreamExecutionEnvironment.getExecutionEnvironment();
        StreamTableEnvironment tEnv = StreamTableEnvironment.getTableEnvironment(env);

        SingleOutputStreamOperator<WC> input = env
                .socketTextStream("localhost", 9000, "\n")
                .map(new MapFunction<String, WC>() {
                    public WC map(String value) throws Exception {
                        String[] row = value.split(",");
                        Timestamp timestamp = Timestamp.valueOf(row[2]);
                        return new WC(row[0], Long.valueOf(row[1]), timestamp);
                .assignTimestampsAndWatermarks(new BoundedOutOfOrdernessTimestampExtractor<WC>(Time.seconds(10)) {
                    public long extractTimestamp(WC element) {
                        return element.dt.getTime();

        tEnv.registerDataStream("WordCount", input, "word, frequency, dt.rowtime");

        Table table = tEnv.scan("WordCount")
                .groupBy("w, word")
                .select("word, frequency.sum as frequency, w.start as dt");

        DataStream<Tuple2<Boolean, WC>> result = tEnv.toRetractStream(table, WC.class);


    public static class WC {
        public String word;
        public long frequency;
        public Timestamp dt;

        public WC() {

        public WC(String word, long frequency, Timestamp dt) {
            this.word = word;
            this.frequency = frequency;
            this.dt = dt;

        public String toString() {
            return "WC " + word + " " + frequency + " " + dt.getTime();

Sample input:

hello,1,2017-12-14 13:10:01
ciao,1,2017-12-14 13:10:02
hello,1,2017-12-14 13:10:03
hello,1,2017-12-14 13:10:04