David Williams David Williams - 7 months ago 101
Scala Question

Kafka Quickstart: What Dependencies do I need?

I am working through the kafka quickstart:

http://kafka.apache.org/07/quickstart.html

and the basic Consumer Group example:

https://cwiki.apache.org/confluence/display/KAFKA/Consumer+Group+Example

I have coded up the Consumer and ConsumerThreadPool as above:

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

public class Consumer implements Runnable {

private KafkaStream m_stream;
private Integer m_threadNumber;

public Consumer(KafkaStream a_stream, Integer a_threadNumber) {
m_threadNumber = a_threadNumber;
m_stream = a_stream;
}

public void run() {
ConsumerIterator<byte[], byte[]> it = m_stream.iterator();
while (it.hasNext()) {
System.out.println("Thread " + m_threadNumber + ": " + new String(it.next().message()));

}
System.out.println("Shutting down Thread: " + m_threadNumber);
}
}


A couple of other facets: I am using spring to manage my zookeeper:

import javax.inject.Named;
import java.util.Properties;
import kafka.consumer.ConsumerConfig;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.ComponentScan;
import org.springframework.context.annotation.Configuration;

@Configuration
@ComponentScan("com.truecar.inventory.worker.core")
public class AppConfig {

@Bean
@Named("consumerConfig")
private static ConsumerConfig createConsumerConfig() {
String zookeeperAddress = "127.0.0.1:2181";
String groupId = "inventory";
Properties props = new Properties();
props.put("zookeeper.connect", zookeeperAddress);
props.put("group.id", groupId);
props.put("zookeeper.session.timeout.ms", "400");
props.put("zookeeper.sync.time.ms", "200");
props.put("auto.commit.interval.ms", "1000");
return new ConsumerConfig(props);
}
}


And I am compiling with Maven and the OneJar Maven plugin. However, I compile and then run the resulting one jar I get the following error:

Aug 26, 2013 6:15:41 PM org.springframework.context.annotation.ClassPathScanningCandidateComponentProvider registerDefaultFilters
INFO: JSR-330 'javax.inject.Named' annotation found and supported for component scanning
Exception in thread "main" java.lang.reflect.InvocationTargetException
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:606)
at com.simontuffs.onejar.Boot.run(Boot.java:340)
at com.simontuffs.onejar.Boot.main(Boot.java:166)
Caused by: java.lang.NoClassDefFoundError: scala/ScalaObject
at java.lang.ClassLoader.defineClass1(Native Method)
at java.lang.ClassLoader.defineClass(ClassLoader.java:792)
at com.simontuffs.onejar.JarClassLoader.defineClass(JarClassLoader.java:803)
at com.simontuffs.onejar.JarClassLoader.findClass(JarClassLoader.java:710)
at java.lang.ClassLoader.loadClass(ClassLoader.java:424)
at com.simontuffs.onejar.JarClassLoader.loadClass(JarClassLoader.java:630)
at java.lang.ClassLoader.loadClass(ClassLoader.java:357)
at java.lang.Class.getDeclaredMethods0(Native Method)
at java.lang.Class.privateGetDeclaredMethods(Class.java:2521)
at java.lang.Class.getDeclaredMethods(Class.java:1845)
at org.springframework.core.type.StandardAnnotationMetadata.getAnnotatedMethods(StandardAnnotationMetadata.java:180)
at org.springframework.context.annotation.ConfigurationClassParser.doProcessConfigurationClass(ConfigurationClassParser.java:222)
at org.springframework.context.annotation.ConfigurationClassParser.processConfigurationClass(ConfigurationClassParser.java:165)
at org.springframework.context.annotation.ConfigurationClassParser.parse(ConfigurationClassParser.java:140)
at org.springframework.context.annotation.ConfigurationClassPostProcessor.processConfigBeanDefinitions(ConfigurationClassPostProcessor.java:282)
at org.springframework.context.annotation.ConfigurationClassPostProcessor.postProcessBeanDefinitionRegistry(ConfigurationClassPostProcessor.java:223)
at org.springframework.context.support.AbstractApplicationContext.invokeBeanFactoryPostProcessors(AbstractApplicationContext.java:630)
at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:461)
at org.springframework.context.annotation.AnnotationConfigApplicationContext.<init>(AnnotationConfigApplicationContext.java:73)
at com.truecar.inventory.worker.core.consumer.ConsumerThreadPool.<clinit>(ConsumerThreadPool.java:31)
at com.truecar.inventory.worker.core.application.Starter.main(Starter.java:20)
... 6 more
Caused by: java.lang.ClassNotFoundException: scala.ScalaObject
at com.simontuffs.onejar.JarClassLoader.findClass(JarClassLoader.java:713)
at java.lang.ClassLoader.loadClass(ClassLoader.java:424)
at com.simontuffs.onejar.JarClassLoader.loadClass(JarClassLoader.java:630)
at java.lang.ClassLoader.loadClass(ClassLoader.java:357)
... 27 more


Now, I know little about Kafka, and nothing about Scala. How do I fix this? What should i try next? Is this a known issue? Do I need other dependencies? Here is the kafka version in my pom.xml:

<dependency>
<groupId>org.apache.kafka</groupId>
<artifactId>kafka_2.9.2</artifactId>
<version>0.8.0-beta1</version>
</dependency>


Update: I contacted the Kafka dev mailing list, and they let me know some specific version requirements for the scala dependencies. However, there is also an undocumented log4j dependency, which results in another runtime, not compile time, exception.

Exception in thread "main" java.lang.reflect.InvocationTargetException
Caused by: java.lang.NoSuchMethodError: ch.qos.logback.classic.Logger.filterAndLog(Ljava/lang/String;Lorg/slf4j/Marker;Lch/qos/logback/classic/Level;Ljava/lang/String;[Ljava/lang/Object;Ljava/lang/Throwable;)V
at org.apache.log4j.Category.log(Category.java:333)
at org.apache.commons.logging.impl.Log4JLogger.debug(Log4JLogger.java:177)


Another Update:

I found the correct log4j dependency:

<dependency>
<groupId>log4j</groupId>
<artifactId>log4j</artifactId>
<version>1.2.17</version>
</dependency>


But now I am met with an even more cryptic runtime exception:

Exception in thread "main" java.lang.reflect.InvocationTargetException
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:606)
at com.simontuffs.onejar.Boot.run(Boot.java:340)
at com.simontuffs.onejar.Boot.main(Boot.java:166)
Caused by: java.lang.NoClassDefFoundError: org/I0Itec/zkclient/IZkStateListener
at kafka.javaapi.consumer.ZookeeperConsumerConnector.<init>(ZookeeperConsumerConnector.scala:64)
at kafka.javaapi.consumer.ZookeeperConsumerConnector.<init>(ZookeeperConsumerConnector.scala:66)
at kafka.consumer.Consumer$.createJavaConsumerConnector(ConsumerConnector.scala:100)
at kafka.consumer.Consumer.createJavaConsumerConnector(ConsumerConnector.scala)


At this point I got the WTF kind of feeling. So I added another dependency:

<dependency>
<groupId>com.101tec</groupId>
<artifactId>zkclient</artifactId>
<version>0.3</version>
</dependency>


But this exposed yet another runtime exception:

Exception in thread "main" java.lang.reflect.InvocationTargetException
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:606)
at com.simontuffs.onejar.Boot.run(Boot.java:340)
at com.simontuffs.onejar.Boot.main(Boot.java:166)
Caused by: java.lang.NoClassDefFoundError: com/yammer/metrics/core/Gauge
at kafka.consumer.ZookeeperConsumerConnector.createFetcher(ZookeeperConsumerConnector.scala:146)
at kafka.consumer.ZookeeperConsumerConnector.<init>(ZookeeperConsumerConnector.scala:113)
at kafka.javaapi.consumer.ZookeeperConsumerConnector.<init>(ZookeeperConsumerConnector.scala:64)
at kafka.javaapi.consumer.ZookeeperConsumerConnector.<init>(ZookeeperConsumerConnector.scala:66)
at kafka.consumer.Consumer$.createJavaConsumerConnector(ConsumerConnector.scala:100)
at kafka.consumer.Consumer.createJavaConsumerConnector(ConsumerConnector.scala)


I am hoping to be able to get this baby example up and running, but maybe this is the price to pay for using beta products? Maybe I should switch to Apache Active MQ. But that sounds less fun. Am I missing something?

Answer Source

The problem is that kafka beta was built in a way that pom generated with a jar isn't valid and maven could not recognize it and parse properly, thus fetching transitive dependencies. We've managed to mitigate this problem by enlisting all of the dependencies from that pom (scala, zk, etc) in our pom definition. We're waiting for next beta builds of kafka, in which problem will be fixed.

Full dependencies list is below. Note that you have to change scala version dependency accordingly to the postfix of your kafka artifact.

<dependency>
            <groupId>org.scala-lang</groupId>
            <artifactId>scala-library</artifactId>
            <version>2.8.0</version>
        </dependency>
        <dependency>
            <groupId>log4j</groupId>
            <artifactId>log4j</artifactId>
            <version>1.2.15</version>
            <exclusions>
                <exclusion>
                    <groupId>com.sun.jmx</groupId>
                    <artifactId>jmxri</artifactId>
                </exclusion>
                <exclusion>
                    <groupId>com.sun.jdmk</groupId>
                    <artifactId>jmxtools</artifactId>
                </exclusion>
                <exclusion>
                    <groupId>javax.jms</groupId>
                    <artifactId>jms</artifactId>
                </exclusion>
            </exclusions>
        </dependency>
        <dependency>
            <groupId>net.sf.jopt-simple</groupId>
            <artifactId>jopt-simple</artifactId>
            <version>3.2</version>
        </dependency>
        <dependency>
            <groupId>org.slf4j</groupId>
            <artifactId>slf4j-simple</artifactId>
            <version>1.6.4</version>
        </dependency>
        <dependency>
            <groupId>org.scala-lang</groupId>
            <artifactId>scala-compiler</artifactId>
            <version>2.8.0</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>
        <dependency>
            <groupId>com.yammer.metrics</groupId>
            <artifactId>metrics-annotation</artifactId>
            <version>2.2.0</version>
        </dependency>
        <dependency>
            <groupId>org.easymock</groupId>
            <artifactId>easymock</artifactId>
            <version>3.0</version>
            <scope>test</scope>
        </dependency>
        <dependency>
            <groupId>org.scalatest</groupId>
            <artifactId>scalatest</artifactId>
            <version>1.2</version>
            <scope>test</scope>
        </dependency>

As for the

Maybe I should switch to Apache Active MQ. But that sounds less fun. Am I missing something?

Well, don't you forget that this is the beta release? Some bad things are happening, indeed, but currently we're running kafka 0.7 without any efforts.

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