CEPTest.java

package com.mycorp.flink;

import java.util.Date;
import java.util.Map;

import org.apache.flink.api.common.functions.FlatMapFunction;
import org.apache.flink.cep.CEP;
import org.apache.flink.cep.PatternSelectFunction;
import org.apache.flink.cep.PatternStream;
import org.apache.flink.cep.PatternTimeoutFunction;
import org.apache.flink.cep.pattern.Pattern;
import org.apache.flink.streaming.api.TimeCharacteristic;
import org.apache.flink.streaming.api.datastream.DataStream;
import org.apache.flink.streaming.api.environment.StreamExecutionEnvironment;
import org.apache.flink.streaming.api.functions.timestamps.AscendingTimestampExtractor;
import org.apache.flink.streaming.api.watermark.Watermark;
import org.apache.flink.streaming.api.windowing.time.Time;
import org.apache.flink.types.Either;
import org.apache.flink.util.Collector;

/**
 * <p>
 * To start an example socket text stream on your local machine run netcat from a command line:
 * <code>nc -lk 9999</code>, where the parameter specifies the port number.
 */
public class CEPTest {

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

        if (args.length != 2) {
            System.err.println("USAGE:\nCEPTest <hostname> <port>");
            return;
        }

        String hostName = args[0];
        Integer port = Integer.parseInt(args[1]);

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

        // Enable to use event time rather than processing time.
        env.setStreamTimeCharacteristic(TimeCharacteristic.EventTime);

        // The pattern.
        Pattern<Event, Event> pattern = Pattern.<Event>begin("start")
                .where(evt -> evt.key.length() > 0)
                .next("last").where(evt -> evt.key.length() > 0).within(Time.seconds(3));

        // Read lines from socket.
        DataStream<String> text = env.socketTextStream(hostName, port);

        // Add tmst, key by input line.
        DataStream<Event> tuples = text.flatMap(new EventExtractor()).keyBy("key");

        // Extract tmst, key by input key.
        DataStream<Event> withTimestampsAndWatermarks = tuples
                .assignTimestampsAndWatermarks(new AscendingTimestampExtractor<Event>() {

                    @Override
                    public long extractAscendingTimestamp(Event element) {
                        return element.tmst;
                    }
                }).keyBy("key");

        // Apply pattern filtering on stream.
        PatternStream<Event> patternStream = CEP.pattern(withTimestampsAndWatermarks, pattern);

        // Select.
        DataStream<Either<String, String>> result = patternStream.select(

                new PatternTimeoutFunction<Event, String>() {

                    @Override
                    public String timeout(Map<String, Event> arg0, long arg1) throws Exception {
                        String out = "Timeout\n";
                        for (Map.Entry<String, Event> e: arg0.entrySet()) {
                            out += String.format("%s:%s\n", e.getKey(), e.getValue());
                        }
                        return out + String.format("at: %s.", new Date(arg1));
                    }

                },

                new PatternSelectFunction<Event, String>() {

                    @Override
                    public String select(Map<String, Event> arg0) throws Exception {
                        String out = "Match\n";
                        for (Map.Entry<String, Event> e: arg0.entrySet()) {
                            out += String.format("%s:%s\n", e.getKey(), e.getValue());
                        }
                        return out;
                    }
                });

        result.print();

        env.execute("Flink CEP test.");
    }

    /**
     * Just emit (input text, tmst) tuple.
     */
    public static final class EventExtractor implements FlatMapFunction<String, Event> {

        @Override
        public void flatMap(String value, Collector<Event> out) {
            String splits[] = value.split(" ");
            out.collect(new Event(splits[0], splits[1]));
        }
    }

    /**
     * Event
     */
    public static final class Event {

        public String key;
        public String value;
        public long tmst;

        public Event() {
        }

        public Event(String key, String value) {
            this.key = key;
            this.value = value;
            this.tmst = System.currentTimeMillis();
        }

        @Override
        public String toString() {
            return String.format("key: %s, value: %s, tmst: %s", key, value, new Date(tmst));
        }

    }

}