Kafka Streams开发入门(3)

 背景

上一篇我们介绍了Kafka Streams中的消息过滤操作filter,今天我们展示一个对消息进行转换Key的操作,依然是结合一个具体的实例展开介绍。所谓转换Key是指对流处理中每条消息的Key进行变换操作,以方便后面进行各种groupByKey操作。

 演示功能说明

本篇演示selectKey的用法,即根据指定的Key选择逻辑对每条消息的Key进行变换操作。今天使用的输入topic消息格式如下:

ID | First Name | Last Name | Phone Number

比如这样:

3 | San | Zhang | 13910010000

我们的目标是提取出手机号的号段(比如1391)作为消息的新Key,然后输出到一个新的Kafka主题上。

 初始化项目  

 创建项目目录:

mkdir selectKey-streams
cd selectKey-streams/

 配置项目

在selectKey-streams目录下创建build.gradle文件,内容如下:

buildscript {

    repositories {

        jcenter()

    }

    dependencies {

        classpath 'com.github.jengelman.gradle.plugins:shadow:4.0.2'

    }

}

 

plugins {

    id 'java'

}

apply plugin: 'com.github.johnrengelman.shadow'

 

repositories {

    mavenCentral()

    jcenter()

 

    maven {

        url 'http://packages.confluent.io/maven'

    }

}

 

group 'huxihx.kafkastreams'

 

sourceCompatibility = 1.8

targetCompatibility = '1.8'

version = '0.0.1'

 

dependencies {

    implementation 'org.slf4j:slf4j-simple:1.7.26'

    implementation 'org.apache.kafka:kafka-streams:2.3.0'

    testCompile group: 'junit', name: 'junit', version: '4.12'

}

 

jar {

    manifest {

        attributes(

                'Class-Path': configurations.compile.collect { it.getName() }.join(' '),

                'Main-Class': 'huxihx.kafkastreams.SelectKeyStreamsApp'

        )

    }

}

 

shadowJar {

    archiveName = "kstreams-transform-standalone-${version}.${extension}"

}

 然后执行下列命令下载Gradle的wrapper套件:

gradle wrapper

之后在selectKey-streams目录下创建一个名为configuration的文件夹用于保存我们的参数配置文件:

mkdir configuration

创建一个名为dev.properties的文件:

application.id=selectKey-app
bootstrap.servers=localhost:9092

input.topic.name=nonkeyed-records
input.topic.partitions=1
input.topic.replication.factor=1

output.topic.name=keyed-records
output.topic.partitions=1
output.topic.replication.factor=1

 开发主流程

 创建src/main/java/huxihx/kafkastreams目录,并在该目录下创建SelectKeyStreamsApp.java文件:

 

package huxihx.kafkastreams;

import org.apache.kafka.clients.admin.AdminClient;
import org.apache.kafka.clients.admin.NewTopic;
import org.apache.kafka.common.serialization.Serdes;
import org.apache.kafka.streams.KafkaStreams;
import org.apache.kafka.streams.StreamsBuilder;
import org.apache.kafka.streams.StreamsConfig;
import org.apache.kafka.streams.Topology;
import org.apache.kafka.streams.kstream.Consumed;

import java.io.FileInputStream;
import java.io.IOException;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.Properties;
import java.util.Set;
import java.util.concurrent.CountDownLatch;

public class SelectKeyStreamsApp {

    public static void main(String[] args) throws Exception {
        if (args.length < 1) {
            throw new IllegalArgumentException("Environment configuration file must be specified.");
        }

        SelectKeyStreamsApp app = new SelectKeyStreamsApp();
        Properties envProps = app.loadEnvProperties(args[0]);
        Properties streamProps = app.buildStreamsProperties(envProps);

        app.preCreateTopics(envProps);

        Topology topology = app.buildTopology(envProps);

        final KafkaStreams streams = new KafkaStreams(topology, streamProps);
        final CountDownLatch latch = new CountDownLatch(1);

        Runtime.getRuntime().addShutdownHook(new Thread("streams-jvm-shutdown-hook") {
            @Override
            public void run() {
                streams.close();
                latch.countDown();
            }
        });

        try {
            streams.start();
            latch.await();
        } catch (Exception e) {
            System.exit(1);
        }
        System.exit(0);
    }

    private Topology buildTopology(Properties envProps) {
        final StreamsBuilder builder = new StreamsBuilder();

        final String inputTopic = envProps.getProperty("input.topic.name");
        final String outputTopic = envProps.getProperty("output.topic.name");

        builder.stream(inputTopic, Consumed.with(Serdes.String(), Serdes.String()))
                .selectKey((noKey, value) -> {
                    String[] fields = value.split("\\|");
                    return fields[fields.length - 1].trim().substring(0, 4);
                })
                .to(outputTopic);
        return builder.build();
    }

    private Properties buildStreamsProperties(Properties envProps) {
        Properties props = new Properties();
        props.put(StreamsConfig.APPLICATION_ID_CONFIG, envProps.getProperty("application.id"));
        props.put(StreamsConfig.BOOTSTRAP_SERVERS_CONFIG, envProps.getProperty("bootstrap.servers"));
        props.put(StreamsConfig.DEFAULT_KEY_SERDE_CLASS_CONFIG, Serdes.String().getClass());
        props.put(StreamsConfig.DEFAULT_VALUE_SERDE_CLASS_CONFIG, Serdes.String().getClass());
        return props;
    }

    private void preCreateTopics(Properties envProps) throws Exception {
        Map<String, Object> config = new HashMap<>();
        config.put("bootstrap.servers", envProps.getProperty("bootstrap.servers"));
        try (AdminClient client = AdminClient.create(config)) {
            Set<String> existingTopics = client.listTopics().names().get();

            List<NewTopic> topics = new ArrayList<>();
            String inputTopic = envProps.getProperty("input.topic.name");
            if (!existingTopics.contains(inputTopic)) {
                topics.add(new NewTopic(inputTopic,
                        Integer.parseInt(envProps.getProperty("input.topic.partitions")),
                        Short.parseShort(envProps.getProperty("input.topic.replication.factor"))));

            }

            String outputTopic = envProps.getProperty("output.topic.name");
            if (!existingTopics.contains(outputTopic)) {
                topics.add(new NewTopic(outputTopic,
                        Integer.parseInt(envProps.getProperty("output.topic.partitions")),
                        Short.parseShort(envProps.getProperty("output.topic.replication.factor"))));
            }

            client.createTopics(topics);
        }
    }

    private Properties loadEnvProperties(String filePath) throws IOException {
        Properties envProps = new Properties();
        try (FileInputStream input = new FileInputStream(filePath)) {
            envProps.load(input);
        }
        return envProps;
    }
}

 测试

首先我们运行下列命令构建项目:

./gradlew clean shadowJar

然后启动Kafka集群,之后运行Kafka Streams应用:

java -jar build/libs/kstreams-transform-standalone-0.0.1.jar configuration/dev.properties

之后启动一个Console Consumer去测试输出topic的Key值是否真的设置了我们的手机号段:

bin/kafka-console-consumer.sh --bootstrap-server localhost:9092 --topic keyed-records --property print.key=true

最后启动一个Console Producer按照规定的事件格式去生成对应的消息:

bin/kafka-console-producer.sh --broker-list localhost:9092 --topic nonkeyed-records

>1 | Wang | Wu | 18601234567
>2 | Li | Si | 13901234567
>3 | Zhang | San | 13921234567
>4 | Alice | Joe | 13901234568

如果一切正常,你应该可以在Console Consumer的输出中看到:

1860 1 | Wang | Wu | 18601234567
1390 2 | Li | Si | 13901234567
1390 3 | Zhang | San | 13921234567
1390 4 | Alice | Joe | 13901234568

前面的4位数字就是我们提取的手机号段信息。后面你可以使用这个Key进行各种groupBy操作,比如统计各个号段的人数等。

总结

很多场合下我们都需要修改原始消息中的Key值,方便后续进行统计操作。本例演示了如何使用selectKey函数方便地对消息Key进行变换。

posted @ 2019-10-12 14:35  huxihx  阅读(674)  评论(0编辑  收藏  举报