Question

出于某种原因，我在尝试使用Cassandra作为Hadoop的输入时遇到以下异常

Exception in thread "main" java.lang.NoClassDefFoundError: com/datastax/driver/core/policies/LoadBalancingPolicy

这是代码

public class CDriver extends Configured implements Tool{

public static void main(String[] args) throws IOException, InterruptedException, ClassNotFoundException, Exception
{
    Configuration conf = new Configuration();

    ToolRunner.run(new CDriver(), args);
}

@Override
public int run(String[] args) throws Exception {

    String output = args[0];

    Configuration conf = super.getConf();

    Job job = new Job(conf);

    job.setJarByClass(CDriver.class);
    job.setJobName("Cassandra as input");

    ConfigHelper.setInputInitialAddress(conf, "127.0.0.1");
    ConfigHelper.setInputColumnFamily(conf, "basketball", "nba");
    ConfigHelper.setInputPartitioner(conf, "Murmur3Partitioner");
    CqlConfigHelper.setInputCQLPageRowSize(conf, "3");
    job.setInputFormatClass(CqlInputFormat.class);

    FileOutputFormat.setOutputPath(job, new Path(output));

    job.setMapperClass(CMapper.class);
    job.setReducerClass(CReducer.class);

    job.setMapOutputKeyClass(Text.class);
    job.setMapOutputValueClass(IntWritable.class);

    job.setOutputKeyClass(Text.class);
    job.setOutputValueClass(IntWritable.class);

    job.waitForCompletion(true);

    return 0;
}

}

以下一行

CqlConfigHelper.setInputCQLPageRowSize(conf, "3");

以下是Maven依赖项：

    <?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>com.nissatech</groupId>
    <artifactId>TestingCassandra</artifactId>
    <version>1.0-SNAPSHOT</version>
    <packaging>jar</packaging>
    <properties>
        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
        <maven.compiler.source>1.7</maven.compiler.source>
        <maven.compiler.target>1.7</maven.compiler.target>
    </properties>
    <dependencies>
        <dependency>
            <groupId>org.apache.hadoop</groupId>
            <artifactId>hadoop-core</artifactId>
            <version>1.2.1</version>
        </dependency>
        <dependency>
            <groupId>org.apache.cassandra</groupId>
            <artifactId>cassandra-all</artifactId>
            <version>2.1.5</version>
        </dependency>
    </dependencies>
    <build>
        <plugins>
            <plugin>
                <artifactId>maven-assembly-plugin</artifactId>
                <configuration>
                    <archive>
                        <manifest>
                            <mainClass>com.nissatech.testingcassandra.CDriver</mainClass>
                        </manifest>
                    </archive>
                    <descriptorRefs>
                        <descriptorRef>
                            jar-with-dependencies
                        </descriptorRef>
                    </descriptorRefs>
                </configuration>
                <executions>
                    <execution>
                        <id>make-assembly</id>
                        <phase>package</phase>
                        <goals>
                            <goal>single</goal>
                        </goals>
                    </execution>
                </executions>
            </plugin>
        </plugins>
    </build>
</project>

任何人都可以解释是什么问题？我让Cassandra在localhost上运行。

Answer 1

您还需要在pom.xml中包含Datastax Java驱动程序作为第三方依赖项。见https://github.com/datastax/java-driver#maven。如果你将它作为传递依赖，请确保使用正确的版本。

Cassandra作为Hadoop作业异常的输入

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