hadoop上的FileNotFoundException

Question

在我的map函数中，我试图从distributedcache中读取一个文件，将其内容加载到哈希映射中。

MapReduce作业的sys输出日志打印HashMap的内容。这表明它已经找到了文件，已经加载到数据结构中并执行了所需的操作。它遍历列表并打印其内容。从而证明手术是成功的。

13/01/27 18:44:21 INFO mapred.JobClient: Task Id : attempt_201301271841_0001_m_000001_2, Status : FAILED
java.io.FileNotFoundException: File does not exist: /app/hadoop/jobs/nw_single_pred_in/predict
    at org.apache.hadoop.hdfs.DFSClient$DFSInputStream.openInfo(DFSClient.java:1843)
    at org.apache.hadoop.hdfs.DFSClient$DFSInputStream.(DFSClient.java:1834)
    at org.apache.hadoop.hdfs.DFSClient.open(DFSClient.java:578)
    at org.apache.hadoop.hdfs.DistributedFileSystem.open(DistributedFileSystem.java:154)
    at org.apache.hadoop.fs.FileSystem.open(FileSystem.java:427)
    at org.apache.hadoop.mapreduce.lib.input.LineRecordReader.initialize(LineRecordReader.java:67)
    at org.apache.hadoop.mapred.MapTask$NewTrackingRecordReader.initialize(MapTask.java:522)
    at org.apache.hadoop.mapred.MapTask.runNewMapper(MapTask.java:763)
    at org.apache.hadoop.mapred.MapTask.run(MapTask.java:370)
    at org.apache.hadoop.mapred.Child$4.run(Child.java:255)
    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:1121)
    at org.apache.hadoop.mapred.Child.main(Child.java:249)

    // inside main, surrounded by try catch block, yet no exception thrown here
        Configuration conf = new Configuration();
        // rest of the stuff that relates to conf
        Path knowledgefilepath = new Path(args[3]); // args[3] = /app/hadoop/jobs/nw_single_pred_in/predict/knowledge.txt
        DistributedCache.addCacheFile(knowledgefilepath.toUri(), conf);
        job.setJarByClass(NBprediction.class);
        // rest of job settings 
        job.waitForCompletion(true); // kick off load

    try {
    System.out.println("Inside try !!");
    Path files[]= DistributedCache.getLocalCacheFiles(context.getConfiguration());
    Path cfile = new Path(files[0].toString()); // only one file
    System.out.println("File path : "+cfile.toString());
    CSVReader reader = new CSVReader(new FileReader(cfile.toString()),'\t');
    while ((nline=reader.readNext())!=null)
    data.put(nline[0],Double.parseDouble(nline[1])); // load into a hashmap
    }
    catch (Exception e)
    {// handle exception }

感谢帮助。

干杯！

Answer 1

重新安装hadoop并使用相同的jar运行该作业后，问题就消失了。似乎是一个bug而不是编程错误。