在本地/远程集群上运行java hadoop作业

Question

我正在尝试在本地/远程集群上运行 hadoop 作业。将来这项工作将通过网络应用程序执行。我正在尝试从 eclipse 执行这段代码：

public class TestHadoop {

    private final static String host = "localhost";

    public static void main(String[] args) throws IOException, InterruptedException, ClassNotFoundException {
        run();
    }

    static void run() throws IOException, InterruptedException, ClassNotFoundException {
        Configuration conf = new Configuration();

        // run on other machine/cluster
        conf.set("fs.default.name", "hdfs://" + host + ":8020");
        conf.set("mapred.job.tracker", "hdfs://" + host + ":8021");

        Job job = new Job(conf, "Wordcount");
        job.setJarByClass(TestHadoop.class);

        FileInputFormat.addInputPath(job, new Path("/user/hue/jobsub/sample_data/midsummer.txt"));
        FileOutputFormat.setOutputPath(job, new Path("/tmp/hadoop-out2"));

        job.setMapperClass(Map.class);
        job.setReducerClass(Reduce.class);

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

        job.setInputFormatClass(TextInputFormat.class);
        job.setOutputFormatClass(TextOutputFormat.class);

        job.waitForCompletion(true);
    }

    static class Map extends Mapper<LongWritable, Text, Text, IntWritable> { 
        private final static IntWritable one = new IntWritable(1);
        private Text word = new Text();

        @Override
        public void map(LongWritable key, Text value, Context context) throws IOException, InterruptedException {
            String line = value.toString();
            StringTokenizer tokenizer = new StringTokenizer(line);
            while (tokenizer.hasMoreTokens()) {
                word.set(tokenizer.nextToken());
                context.write(word, one);
            }
        }
    }

    static class Reduce extends Reducer<Text, IntWritable, Text, IntWritable> { 

        @Override
        public void reduce(Text key, Iterable<IntWritable> values, Context context) throws IOException,
                InterruptedException {
            int sum = 0;
            for (IntWritable val : values) {
                sum += val.get();
            }
            context.write(key, new IntWritable(sum));
        }
    }
}

但是出现以下错误：

2011-09-30 16:32:39,000 WARN org.apache.hadoop.mapred.Child: Error running child
java.lang.RuntimeException: java.lang.ClassNotFoundException: org.mmm.hadoop.TestHadoop$Map
at org.apache.hadoop.conf.Configuration.getClass(Configuration.java:996)
at org.apache.hadoop.mapreduce.JobContext.getMapperClass(JobContext.java:212)
at org.apache.hadoop.mapred.MapTask.runNewMapper(MapTask.java:602)
at org.apache.hadoop.mapred.MapTask.run(MapTask.java:323)
at org.apache.hadoop.mapred.Child$4.run(Child.java:270)
at java.security.AccessController.doPrivileged(Native Method)
at javax.security.auth.Subject.doAs(Subject.java:396)
at org.apache.hadoop.security.UserGroupInformation.doAs(UserGroupInformation.java:1127)
at org.apache.hadoop.mapred.Child.main(Child.java:264)
Caused by: java.lang.ClassNotFoundException: org.mmm.hadoop.TestHadoop$Map
at java.net.URLClassLoader$1.run(URLClassLoader.java:202)
at java.security.AccessController.doPrivileged(Native Method)
at java.net.URLClassLoader.findClass(URLClassLoader.java:190)
at java.lang.ClassLoader.loadClass(ClassLoader.java:306)
at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:301)
at java.lang.ClassLoader.loadClass(ClassLoader.java:247)
at java.lang.Class.forName0(Native Method)
at java.lang.Class.forName(Class.java:247)
at org.apache.hadoop.conf.Configuration.getClassByName(Configuration.java:943)
at org.apache.hadoop.conf.Configuration.getClass(Configuration.java:994)
... 8 more

16:33:01.209 [LeaseChecker] DEBUG org.apache.hadoop.hdfs.DFSClient - LeaseChecker is interrupted.
java.lang.InterruptedException: sleep interrupted
    at java.lang.Thread.sleep(Native Method) [na:1.7.0]
    at org.apache.hadoop.hdfs.DFSClient$LeaseChecker.run(DFSClient.java:1167) ~[hadoop-core-0.20.2-cdh3u1.jar:na]
    at java.lang.Thread.run(Thread.java:722) [na:1.7.0]

我正在将 CDH3 与 Hue 一起使用。作业出现在作业列表中，并带有上述正在运行的子错误。

Answer 1

您必须将自定义映射器/减速器实现捆绑在 jar 中。

job.setJarByClass(TestHadoop.class); 

然后将查找该 jar 并将其传输到集群。

Answer 2

我知道我可能已经太晚了，但也尝试将 Map 和 Reduce 声明为公共。

Answer 3

mapred.job.tracker url应该是http而不是hdfs...

并使Mapper和Reducer公开..

//error 
conf.set("mapred.job.tracker", "hdfs://" + host + ":8021");