无法创建多个流消费者

无法创建多个流消费者

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Kafka:无法创建多个流消费者

本文介绍了Kafka:无法创建多个流消费者的处理方法，对大家解决问题具有一定的参考价值，需要的朋友们下面随着小编来一起学习吧！

问题描述

我刚刚启动并运行了 Kafka 0.8 beta 1.我有一个非常简单的示例启动并运行，问题是，我只能让一个消息消费者工作，而不是几个.也就是说， runSingleWorker() 方法有效.run() 方法不起作用:

I just got up and running with Kafka 0.8 beta 1. I have a really simple example up and running, the problem is, I can only get one message consumer to work, not several. That is, the runSingleWorker() method WORKS. The run() method DOES NOT WORK:

import kafka.consumer.ConsumerIterator;
import kafka.consumer.KafkaStream;
import kafka.consumer.ConsumerConfig;
import kafka.javaapi.consumer.ConsumerConnector;

import java.util.Map;
import java.util.List;
import java.util.HashMap;
import java.util.concurrent.Executors;
import java.util.concurrent.ExecutorService;

import org.springframework.context.ApplicationContext;
import org.springframework.context.annotation.AnnotationConfigApplicationContext;

import com.truecar.inventory.worker.core.application.config.AppConfig;

public class ConsumerThreadPool {

    private final ConsumerConnector consumer;
    private final String topic;

    private ExecutorService executor;
    private static ApplicationContext context = new AnnotationConfigApplicationContext(AppConfig.class);

    public ConsumerThreadPool(String topic) {
        consumer = kafka.consumer.Consumer.createJavaConsumerConnector((ConsumerConfig)context.getBean("consumerConfig"));
        this.topic = topic;
    }

    public void shutdown() {
        if (consumer != null) consumer.shutdown();
        if (executor != null) executor.shutdown();
    }

    public void run(Integer numThreads) {
        Map<String, Integer> topicCountMap = new HashMap<String, Integer>();

        topicCountMap.put(topic, numThreads);
        Map<String, List<KafkaStream<byte[], byte[]>>> consumerMap = consumer.createMessageStreams(topicCountMap);
        List<KafkaStream<byte[], byte[]>> topicListeners = consumerMap.get(topic);

        executor = Executors.newFixedThreadPool(numThreads);

        for(Integer i = 0; i < numThreads; i++ ){
            KafkaStream<byte[], byte[]> stream =  topicListeners.get(i);
            executor.submit(new Consumer(stream, i));
        }
    }


    public void runSingleWorker(Integer numThreads) {
        Map<String, Integer> topicCountMap = new HashMap<String, Integer>();

        topicCountMap.put(topic, new Integer(1));

        Map<String, List<KafkaStream<byte[], byte[]>>> consumerMap = consumer.createMessageStreams(topicCountMap);

        KafkaStream<byte[], byte[]> stream =  consumerMap.get(topic).get(0);
        ConsumerIterator<byte[], byte[]> it = stream.iterator();
        while(true) {
            try {
                Thread.sleep(1000);
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
            while(it.hasNext()){
                System.out.println(new String(it.next().message()));

            }
        }
    }
}

在我的玩具消费者内部:

And inside my toy consumer:

import kafka.consumer.KafkaStream;
import kafka.consumer.ConsumerIterator;

public class Consumer implements Runnable {

    private KafkaStream kafkaStream;
    private Integer threadNumber;

    public Consumer(KafkaStream kafkaStream, Integer threadNumber) {
        this.threadNumber = threadNumber;
        this.kafkaStream = kafkaStream;
    }

    public void run() {
        ConsumerIterator<byte[], byte[]> it = kafkaStream.iterator();
        System.out.println("Created iterator " + it.toString() + " thread number " + threadNumber);
        while(true) {

            try {
                Thread.sleep(1000);
            } catch (InterruptedException e) {
                break;
            }

            while(it.hasNext()) {
                System.out.println("Thread " + threadNumber + ": " + new String(it.next().message()));
            }
        }
        System.out.println("Shutting down Thread: " + threadNumber);
    }
}

问题是，worker 池不接收消息:

The problem is, the pool of workers does not pick up messages:

Created iterator empty iterator thread number 3
Created iterator empty iterator thread number 6
Created iterator empty iterator thread number 9
Created iterator empty iterator thread number 7
Created iterator empty iterator thread number 0
Created iterator empty iterator thread number 0
Created iterator empty iterator thread number 8
Created iterator empty iterator thread number 3
etc...

当我通过生产命令行添加消息时，在单线程工作版本下打印消息，但在多流情况下不打印消息.这里发生了什么?我该如何解决这个问题?

When I add messages via the produce command line, the messages are printed under the single threaded worker version, but messages are not printed under the multi-stream situation. Whats going on here? How can I fix this?

顺便说一句，kafka 0.8 的 pom.xml 不是有效的 pom，不会获取依赖，所以这里是一个完全依赖的 pom.

Btw, the pom.xml for kafka 0.8 is not a valid pom and will not acquire dependencies, so here is a pom with complete dependencies.

<?xml version="1.0" encoding="UTF-8"?>
<project
xmlns="http://maven.apache.org/POM/4.0.0"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="
    http://maven.apache.org/POM/4.0.0
    http://maven.apache.org/xsd/maven-4.0.0.xsd">
<modelVersion>4.0.0</modelVersion>
<groupId>group1</groupId>
<artifactId>artifact1</artifactId>
<version>0.1.0</version>
<packaging>jar</packaging>
<properties>
    <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
    <org.springframework.version>3.2.4.RELEASE</org.springframework.version>
</properties>
<dependencies>
    <dependency>
        <groupId>org.springframework</groupId>
        <artifactId>spring-core</artifactId>
        <version>3.2.4.RELEASE</version>
    </dependency>
    <dependency>
        <groupId>org.springframework</groupId>
        <artifactId>spring-context</artifactId>
        <version>3.2.4.RELEASE</version>
    </dependency>
    <dependency>
        <groupId>org.apache.kafka</groupId>
        <artifactId>kafka_2.9.2</artifactId>
        <version>0.8.0-beta1</version>
    </dependency>
    <dependency>
        <groupId>javax.inject</groupId>
        <artifactId>javax.inject</artifactId>
        <version>1</version>
    </dependency>
    <dependency>
        <groupId>org.scala-lang</groupId>
        <artifactId>scala-library</artifactId>
        <version>2.9.2</version>
    </dependency>
    <dependency>
        <groupId>log4j</groupId>
        <artifactId>log4j</artifactId>
        <version>1.2.17</version>
    </dependency>
    <dependency>
        <groupId>com.101tec</groupId>
        <artifactId>zkclient</artifactId>
        <version>0.3</version>
    </dependency>
    <dependency>
        <groupId>com.yammer.metrics</groupId>
        <artifactId>metrics-core</artifactId>
        <version>2.2.0</version>
    </dependency>
</dependencies>
<build>
    <finalName>inventory-core</finalName>
    <plugins>
        <plugin>
            <groupId>org.apache.maven.plugins</groupId>
            <artifactId>maven-compiler-plugin</artifactId>
            <version>3.0</version>
            <configuration>
                <source>1.7</source>
                <target>1.7</target>
            </configuration>
        </plugin>
        <plugin>
            <groupId>org.apache.maven.plugins</groupId>
            <artifactId>maven-jar-plugin</artifactId>
            <configuration>
                <archive>
                    <manifest>
                        <mainClass>com.truecar.inventory.worker.core.application.Starter</mainClass>
                    </manifest>
                </archive>
            </configuration>
        </plugin>
        <plugin>
            <groupId>org.dstovall</groupId>
            <artifactId>onejar-maven-plugin</artifactId>
            <version>1.4.4</version>
            <executions>
                <execution>
                    <configuration>
                        <onejarVersion>0.97</onejarVersion>
                        <classifier>onejar</classifier>
                    </configuration>
                    <goals>
                        <goal>one-jar</goal>
                    </goals>
                </execution>
            </executions>
        </plugin>
    </plugins>
</build>
<pluginRepositories>
    <pluginRepository>
        <id>onejar-maven-plugin.googlecode.com</id>
        <url>http://onejar-maven-plugin.googlecode.com/svn/mavenrepo</url>
    </pluginRepository>
</pluginRepositories>
</project>

推荐答案

对于提问者来说可能为时已晚，但可能对其他开发人员有用.似乎您只为几个消费者使用了一个分区——这是错误的.引用自 文档:

Maybe too late for questioner but could be useful to other developers.Seems you have used only one Partition for couple of Consumers – that's wrong.Quote from Documentation:

由于有许多分区，这仍然可以平衡许多消费者实例的负载.但是请注意，消费者实例不能多于分区.

所以当你考虑消费者时，你应该考虑如何按分区划分消息.在大多数情况下，您应该对其使用一些高级分组，甚至默认情况下让它是随机的.

So when you think about Consumers you should think how to divide messages by partitions.In most cases you should use some high-level grouping to it or even let it be random by default.

这篇关于Kafka:无法创建多个流消费者的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持！

07-28 03:05
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