解決在windows的eclipse上面運行WordCount程序出現的一系列問題詳解

一．簡介

   要在Windows下的 Eclipse上調試Hadoop2代碼，所以我們在windows下的Eclipse配置hadoop-eclipse-plugin- 2.6.0.jar插件，並在運行Hadoop的WordCount代碼時出現了一系列的問題，搞了好幾天終於能運行起代碼。接下來我們來看看問題並怎么解決，提供給跟我同樣遇到的問題作為參考。

Hadoop2的WordCount.java統計代碼如下：

import java.io.IOException;
import java.util.StringTokenizer;

import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.fs.Path;
import org.apache.hadoop.io.IntWritable;
import org.apache.hadoop.io.Text;
import org.apache.hadoop.mapreduce.Job;
import org.apache.hadoop.mapreduce.Mapper;
import org.apache.hadoop.mapreduce.Reducer;
import org.apache.hadoop.mapreduce.lib.input.FileInputFormat;
import org.apache.hadoop.mapreduce.lib.output.FileOutputFormat;

public class WordCount {

  public static class TokenizerMapper
       extends Mapper<Object, Text, Text, IntWritable>{

    private final static IntWritable one = new IntWritable(1);
    private Text word = new Text();

    public void map(Object key, Text value, Context context
                    ) throws IOException, InterruptedException {
      StringTokenizer itr = new StringTokenizer(value.toString());
      while (itr.hasMoreTokens()) {
        word.set(itr.nextToken());
        context.write(word, one);
      }
    }
  }

  public static class IntSumReducer
       extends Reducer<Text,IntWritable,Text,IntWritable> {
    private IntWritable result = new IntWritable();

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

  public static void main(String[] args) throws Exception {
    Configuration conf = new Configuration();
　　 conf.set("mapred.job.tracker", "hadoopmaster:9001");//在windows下面必須設置
    conf.set("fs.default.name", "hdfs://hadoopmaster:9000");
    Job job = Job.getInstance(conf, "word count");
    job.setJarByClass(WordCount.class);
    job.setMapperClass(TokenizerMapper.class);
    job.setCombinerClass(IntSumReducer.class);
    job.setReducerClass(IntSumReducer.class);
    job.setOutputKeyClass(Text.class);
    job.setOutputValueClass(IntWritable.class);
    FileInputFormat.addInputPath(job, new Path(args[0]));
    FileOutputFormat.setOutputPath(job, new Path(args[1]));
    System.exit(job.waitForCompletion(true) ? 0 : 1);
  }
}

問題一.An internal error occurred during: "Map/Reducelocation status updater".java.lang.NullPointerException

把hadoop-eclipse-plugin-2.6.0.jar放到Eclipse的plugins目錄下，我們的Eclipse目錄是 F:\tool\eclipse-jee-juno-SR2\eclipse-jee-juno-SR2\plugins，重啟一下Eclipse，然 后，打開Window-->Preferens，可以看到Hadoop Map/Reduc選項，然后點擊出現了An internal error occurredduring: "Map/Reduce location status updater".java.lang.NullPointerException，如圖所示：

解決：

我們發現剛配置部署的Hadoop2還沒創建輸入和輸出目錄，先在hdfs上建個文件夾 。

#bin/hdfs dfs -mkdir –p /user/root/input

#bin/hdfs dfs -mkdir -p  /user/root/output

 我們在Eclipse的DFS Locations目錄下看到我們這兩個目錄，如圖所示：

問題二.Exception in thread "main" java.lang.NullPointerException atjava.lang.ProcessBuilder.start(Unknown Source)

運行Hadoop2的WordCount.java代碼時出現了這樣錯誤：

log4j:WARNPlease initialize the log4j system properly.
log4j:WARN Seehttp://logging.apache.org/log4j/1.2/faq.html#noconfig for more info.
Exception in thread "main" java.lang.NullPointerException
       atjava.lang.ProcessBuilder.start(Unknown Source)
       atorg.apache.hadoop.util.Shell.runCommand(Shell.java:482)
       atorg.apache.hadoop.util.Shell.run(Shell.java:455)
       atorg.apache.hadoop.util.Shell$ShellCommandExecutor.execute(Shell.java:715)
       atorg.apache.hadoop.util.Shell.execCommand(Shell.java:808)
       atorg.apache.hadoop.util.Shell.execCommand(Shell.java:791)
       at

分析：下載Hadoop2以上版本時，在Hadoop2的bin目錄下沒有winutils.exe

解決：

1.下載https://codeload.github.com/srccodes/hadoop-common-2.2.0-bin/zip /master下載hadoop-common-2.2.0-bin-master.zip，然后解壓后，把hadoop-common-2.2.0- bin-master下的bin全部復制放到我們下載的Hadoop2的binHadoop2/bin目錄下。如圖所示：

2.Eclipse-》window-》Preferences 下的Hadoop Map/Peduce 把下載放在我們的磁盤的Hadoop目錄引進來，如圖所示：

3.Hadoop2配置變量環境HADOOP_HOME 和path，如圖所示：

問題三.Exception in thread "main"java.lang.UnsatisfiedLinkError:org.apache.hadoop.io.nativeio.NativeIO$Windows.access0(Ljava/lang/String;I)Z

當我們解決了問題三時，在運行WordCount.java代碼時，出現這樣的問題:

log4j:WARN No appenders could be found forlogger (org.apache.hadoop.metrics2.lib.MutableMetricsFactory).
log4j:WARN Please initialize the log4jsystem properly.
log4j:WARN Seehttp://logging.apache.org/log4j/1.2/faq.html#noconfig for more info.
Exception in thread "main"java.lang.UnsatisfiedLinkError:org.apache.hadoop.io.nativeio.NativeIO$Windows.access0(Ljava/lang/String;I)Z
       atorg.apache.hadoop.io.nativeio.NativeIO$Windows.access0(Native Method)
       atorg.apache.hadoop.io.nativeio.NativeIO$Windows.access(NativeIO.java:557)
       atorg.apache.hadoop.fs.FileUtil.canRead(FileUtil.java:977)
       atorg.apache.hadoop.util.DiskChecker.checkAccessByFileMethods(DiskChecker.java:187)
       atorg.apache.hadoop.util.DiskChecker.checkDirAccess(DiskChecker.java:174)
       atorg.apache.hadoop.util.DiskChecker.checkDir(DiskChecker.java:108)
       atorg.apache.hadoop.fs.LocalDirAllocator$AllocatorPerContext.confChanged(LocalDirAllocator.java:285)
       atorg.apache.hadoop.fs.LocalDirAllocator$AllocatorPerContext.getLocalPathForWrite(LocalDirAllocator.java:344)
       atorg.apache.hadoop.fs.LocalDirAllocator.getLocalPathForWrite(LocalDirAllocator.java:150)
       atorg.apache.hadoop.fs.LocalDirAllocator.getLocalPathForWrite(LocalDirAllocator.java:131)
       atorg.apache.hadoop.fs.LocalDirAllocator.getLocalPathForWrite(LocalDirAllocator.java:115)
       atorg.apache.hadoop.mapred.LocalDistributedCacheManager.setup(LocalDistributedCacheManager.

分析：C:\Windows\System32下缺少hadoop.dll,把這個文件拷貝到C:\Windows\System32下面即可。

解決：hadoop-common-2.2.0-bin-master下的bin的hadoop.dll放到C:\Windows\System32下，然后重啟電腦，也許還沒那么簡單，還是出現這樣的問題。

我們在繼續分析：我們在出現錯誤的的atorg.apache.hadoop.io.nativeio.NativeIO$Windows.access(NativeIO.java:557)我們來看這個類NativeIO的557行，如圖所示：

Windows的唯一方法用於檢查當前進程的請求，在給定的路徑的訪問權限，所以我們先給以能進行訪問，我們自己先修改源代碼，return true 時允許訪問。我們下載對應hadoop源代碼，hadoop-2.6.0-src.tar.gz解壓，hadoop-2.6.0-src\hadoop- common-project\hadoop-common\src\main\java\org\apache\hadoop\io\nativeio 下NativeIO.java 復制到對應的Eclipse的project，然后修改557行為return true如圖所示：

問題四：org.apache.hadoop.security.AccessControlException: Permissiondenied: user=zhengcy, access=WRITE,inode="/user/root/output":root:supergroup:drwxr-xr-x

我們在執行運行WordCount.java代碼時，出現這樣的問題:

2014-12-18 16:03:24,092  WARN (org.apache.hadoop.mapred.LocalJobRunner:560) - job_local374172562_0001
org.apache.hadoop.security.AccessControlException: Permission denied: user=zhengcy, access=WRITE, inode="/user/root/output":root:supergroup:drwxr-xr-x
    at org.apache.hadoop.hdfs.server.namenode.FSPermissionChecker.checkFsPermission(FSPermissionChecker.java:271)
    at org.apache.hadoop.hdfs.server.namenode.FSPermissionChecker.check(FSPermissionChecker.java:257)
    at org.apache.hadoop.hdfs.server.namenode.FSPermissionChecker.check(FSPermissionChecker.java:238)
    at org.apache.hadoop.hdfs.server.namenode.FSPermissionChecker.checkPermission(FSPermissionChecker.java:179)
    at org.apache.hadoop.hdfs.server.namenode.FSNamesystem.checkPermission(FSNamesystem.java:6512)
    at org.apache.hadoop.hdfs.server.namenode.FSNamesystem.checkPermission(FSNamesystem.java:6494)
    at org.apache.hadoop.hdfs.server.namenode.FSNamesystem.checkAncestorAccess(FSNamesystem.java:6446)
    at org.apache.hadoop.hdfs.server.namenode.FSNamesystem.mkdirsInternal(FSNamesystem.java:4248)
    at org.apache.hadoop.hdfs.server.namenode.FSNamesystem.mkdirsInt(FSNamesystem.java:4218)
    at org.apache.hadoop.hdfs.server.namenode.FSNamesystem.mkdirs(FSNamesystem.java:4191)
    at org.apache.hadoop.hdfs.server.namenode.NameNodeRpcServer.mkdirs(NameNodeRpcServer.java:8

分析：我們沒權限訪問output目錄。

解決：我們 在設置hdfs配置的目錄是在hdfs-site.xml配置hdfs文件存放的地方,我們在這個etc/hadoop下的hdfs-site.xml添加

<property> 
     <name>dfs.permissions</name> 
     <value>false</value> 
  </property>

設置沒有權限，不過我們在正式的 服務器上不能這樣設置。

問題五：File/usr/root/input/file01._COPYING_ could only be replicated to 0 nodes instead ofminRepLication (=1) There are 0 datanode(s) running and no node(s) are excludedin this operation

如圖所示：

分析：  我們在第一次執行#hadoop namenode –format 完然后在執行#sbin/start-all.sh 再執行#jps，能看到Datanode，在執行#hadoop namenode –format然后執行#jps這時看不到Datanode ,如圖所示：

然后我們想把文本放到輸入目錄執行bin/hdfs dfs -put/usr/local/hadoop/hadoop-2.6.0/test/* /user/root/input  把/test/*文件上傳到hdfs的/user/root/input中,出現這樣的問題。

 解決：是我們執行太多次了hadoopnamenode –format，創建了多個，去我們對應的hdfs目錄刪除hdfs-site.xml配置的保存datanode和namenode目錄即可解決。