Flink CEP No Results Printed

Question

I am trying to print out a string if Hello and world are found using the Flink CEP library. My source is Kafka and using the console-producer to input the data. That part is working. I can print out what I enter into the topic. However, it will not print out my final message "The world is so nice!". It will not even print out that it entered the lambda. Below is the class

package kafka;

import org.apache.flink.cep.CEP;
import org.apache.flink.cep.PatternStream;
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.windowing.time.Time;
import org.apache.flink.streaming.connectors.kafka.FlinkKafkaConsumer08;
import org.apache.flink.streaming.util.serialization.SimpleStringSchema;
import org.apache.flink.util.Collector;

import java.util.Map;
import java.util.Properties;

/**
 * Created by crackerman on 9/16/16.
*/
public class WordCount {

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

    Properties properties = new Properties();
    properties.put("bootstrap.servers", "localhost:9092");
    properties.put("zookeeper.connect", "localhost:2181");
    properties.put("group.id", "test");
    StreamExecutionEnvironment see = StreamExecutionEnvironment.getExecutionEnvironment();
    see.setStreamTimeCharacteristic(TimeCharacteristic.EventTime);

    DataStream<String> src = see.addSource(new FlinkKafkaConsumer08<>("complexString",
                                                                      new SimpleStringSchema(),
                                                                      properties));

    src.print();


    Pattern<String, String> pattern = Pattern.<String>begin("first")
            .where(evt -> evt.contains("Hello"))
            .followedBy("second")
            .where(evt -> evt.contains("World"));

    PatternStream<String> patternStream = CEP.pattern(src, pattern);

    DataStream<String> alerts = patternStream.flatSelect(
            (Map<String, String> in, Collector<String> out) -> {
                System.out.println("Made it to the lambda");
                String first = in.get("first");
                String second = in.get("second");
                System.out.println("First: " + first);
                System.out.println("Second: " + second);

                if (first.equals("Hello") && second.equals("World")) {

                    out.collect("The world is so nice!");
                }


            });

    alerts.print();

    see.execute();
}

}

Any help would be greatly appreciated.

Thanks!

score 1 · Answer 1 · answered Sep 19 '16 at 16:08

1

The issue is the following line

 see.setStreamTimeCharacteristic(TimeCharacteristic.EventTime);

If that is removed, it works the way I expected it to.

answered Sep 19 '16 at 16:08

Crackerman

717
1
9
22

2

Did you assign timestamps and watermarks? Event-time mode does only work if you tell Flink the time of each record and how much time has passed. Without this information, Flink is not able to process data in event-time. Event-time is required to produce consistent results if your data arrives out-of-order or if you have time-based operations (e.g. windows). – Fabian Hueske Sep 19 '16 at 18:10
1

I did not assign timestamps and watermarks. I have gone back and implemented this. Thanks for the info! – Crackerman Sep 21 '16 at 15:43

Flink CEP No Results Printed

1 Answers1