├── LICENSE ├── README.md ├── pom.xml └── src └── main ├── java └── com │ └── shapira │ └── examples │ └── streams │ └── wordcount │ └── WordCountExample.java └── resources └── log4j.properties /LICENSE: -------------------------------------------------------------------------------- 1 | Apache License 2 | Version 2.0, January 2004 3 | http://www.apache.org/licenses/ 4 | 5 | TERMS AND CONDITIONS FOR USE, REPRODUCTION, AND DISTRIBUTION 6 | 7 | 1. Definitions. 8 | 9 | "License" shall mean the terms and conditions for use, reproduction, 10 | and distribution as defined by Sections 1 through 9 of this document. 11 | 12 | "Licensor" shall mean the copyright owner or entity authorized by 13 | the copyright owner that is granting the License. 14 | 15 | "Legal Entity" shall mean the union of the acting entity and all 16 | other entities that control, are controlled by, or are under common 17 | control with that entity. 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It is based on Confluent's wordcount example, with very minor changes. You can find the original here: 2 | https://github.com/confluentinc/examples/blob/3.1.x/kafka-streams/src/main/java/io/confluent/examples/streams/WordCountLambdaExample.java 3 | 4 | To run this example: 5 | 6 | 0. Build the project with `mvn package`, this will generate an uber-jar with the streams app and all its dependencies. 7 | 1. Create a wordcount-input topic: 8 | 9 | `bin/kafka-topics.sh --bootstrap-server localhost:9092 --create --topic wordcount-input --partitions 1 --replication-factor 1` 10 | 11 | 2. Produce some text to the topic. Don't forget to repeat words (so we can count higher than 1) and to use the word "the", so we can filter it. 12 | 13 | `bin/kafka-console-producer.sh --broker-list localhost:9092 --topic wordcount-input` 14 | 15 | 3. Run the app: 16 | 17 | `java -cp target/uber-kafka-streams-wordcount-1.0-SNAPSHOT.jar com.shapira.examples.streams.wordcount.WordCountExample` 18 | 19 | 4. Take a look at the results: 20 | 21 | `bin/kafka-console-consumer.sh --topic wordcount-output --from-beginning --bootstrap-server localhost:9092 --property print.key=true` 22 | 23 | If you want to reset state and re-run the application (maybe with some changes?) on existing input topic, you can: 24 | 25 | 1. Reset internal topics (used for shuffle and state-stores): 26 | 27 | `bin/kafka-streams-application-reset.sh --application-id wordcount --bootstrap-servers localhost:9092 --input-topics wordcount-input` 28 | 29 | 2. (optional) Delete the output topic: 30 | 31 | `bin/kafka-topics.sh --bootstrap-server localhost:9092 --delete --topic wordcount-output` 32 | 33 | 34 | 35 | 36 | 37 | -------------------------------------------------------------------------------- /pom.xml: -------------------------------------------------------------------------------- 1 | 2 | 5 | 4.0.0 6 | 7 | streams-wordcount 8 | kafka-streams-wordcount 9 | 1.0-SNAPSHOT 10 | 11 | 12 | 13 | org.apache.kafka 14 | kafka-streams 15 | 2.8.0 16 | 17 | 18 | 19 | 20 | 21 | org.apache.maven.plugins 22 | maven-compiler-plugin 23 | 3.5.1 24 | 25 | 1.8 26 | 1.8 27 | 28 | 29 | 30 | org.apache.maven.plugins 31 | maven-shade-plugin 32 | 33 | 34 | package 35 | 36 | shade 37 | 38 | 39 | 40 | 41 | uber-${artifactId}-${version} 42 | 43 | 44 | 45 | 46 | 47 | -------------------------------------------------------------------------------- /src/main/java/com/shapira/examples/streams/wordcount/WordCountExample.java: -------------------------------------------------------------------------------- 1 | package com.shapira.examples.streams.wordcount; 2 | 3 | 4 | import org.apache.kafka.clients.CommonClientConfigs; 5 | import org.apache.kafka.clients.consumer.ConsumerConfig; 6 | import org.apache.kafka.common.serialization.Serdes; 7 | import org.apache.kafka.streams.KafkaStreams; 8 | import org.apache.kafka.streams.KeyValue; 9 | import org.apache.kafka.streams.StreamsConfig; 10 | import org.apache.kafka.streams.kstream.KStream; 11 | import org.apache.kafka.streams.StreamsBuilder; 12 | import java.util.Arrays; 13 | import java.util.Properties; 14 | import java.util.regex.Pattern; 15 | 16 | public class WordCountExample { 17 | 18 | public static void main(String[] args) throws Exception{ 19 | 20 | Properties props = new Properties(); 21 | props.put(StreamsConfig.APPLICATION_ID_CONFIG, "wordcount"); 22 | props.put(StreamsConfig.BOOTSTRAP_SERVERS_CONFIG, "localhost:9092"); 23 | props.put(StreamsConfig.DEFAULT_KEY_SERDE_CLASS_CONFIG, Serdes.String().getClass().getName()); 24 | props.put(StreamsConfig.DEFAULT_VALUE_SERDE_CLASS_CONFIG, Serdes.String().getClass().getName()); 25 | 26 | // setting offset reset to earliest so that we can re-run the demo code with the same pre-loaded data 27 | // Note: To re-run the demo, you need to use the offset reset tool: 28 | // https://cwiki.apache.org/confluence/display/KAFKA/Kafka+Streams+Application+Reset+Tool 29 | props.put(ConsumerConfig.AUTO_OFFSET_RESET_CONFIG, "earliest"); 30 | 31 | // work-around for an issue around timing of creating internal topics 32 | // Fixed in Kafka 0.10.2.0 33 | // don't use in large production apps - this increases network load 34 | // props.put(CommonClientConfigs.METADATA_MAX_AGE_CONFIG, 500); 35 | 36 | StreamsBuilder builder = new StreamsBuilder(); 37 | 38 | KStream source = builder.stream("wordcount-input"); 39 | 40 | 41 | final Pattern pattern = Pattern.compile("\\W+"); 42 | KStream counts = source.flatMapValues(value-> Arrays.asList(pattern.split(value.toLowerCase()))) 43 | .map((key, value) -> new KeyValue(value, value)) 44 | .filter((key, value) -> (!value.equals("the"))) 45 | .groupByKey() 46 | .count().mapValues(value->Long.toString(value)).toStream(); 47 | counts.to("wordcount-output"); 48 | 49 | KafkaStreams streams = new KafkaStreams(builder.build(), props); 50 | 51 | // This is for reset to work. Don't use in production - it causes the app to re-load the state from Kafka on every start 52 | streams.cleanUp(); 53 | 54 | streams.start(); 55 | 56 | // usually the stream application would be running forever, 57 | // in this example we just let it run for some time and stop since the input data is finite. 58 | Thread.sleep(5000L); 59 | 60 | streams.close(); 61 | 62 | } 63 | } 64 | -------------------------------------------------------------------------------- /src/main/resources/log4j.properties: -------------------------------------------------------------------------------- 1 | log4j.rootLogger=TRACE, stderr 2 | 3 | log4j.appender.stderr=org.apache.log4j.ConsoleAppender 4 | log4j.appender.stderr.layout=org.apache.log4j.PatternLayout 5 | log4j.appender.stderr.layout.ConversionPattern=[%d] %p %m (%c)%n 6 | log4j.appender.stderr.Target=System.err --------------------------------------------------------------------------------