Yongjun Zhang created HDFS-9670:
-----------------------------------

             Summary: DistCp throws NPE when source is root "/"
                 Key: HDFS-9670
                 URL: https://issues.apache.org/jira/browse/HDFS-9670
             Project: Hadoop HDFS
          Issue Type: Bug
            Reporter: Yongjun Zhang
            Assignee: Yongjun Zhang


Symptom:

[root@vb0724 ~]# hadoop distcp hdfs://X:8020/ hdfs://Y:8020/
16/01/20 11:33:33 INFO tools.DistCp: Input Options: 
DistCpOptions{atomicCommit=false, syncFolder=false, deleteMissing=false, 
ignoreFailures=false, maxMaps=20, sslConfigurationFile='null', 
copyStrategy='uniformsize', sourceFileListing=null, 
sourcePaths=[hdfs://X:8020/], targetPath=hdfs://Y:8020/, targetPathExists=true, 
preserveRawXattrs=false, filtersFile='null'}
16/01/20 11:33:33 INFO client.RMProxy: Connecting to ResourceManager at Z:8032
16/01/20 11:33:33 ERROR tools.DistCp: Exception encountered 
java.lang.NullPointerException
  at 
org.apache.hadoop.tools.util.DistCpUtils.getRelativePath(DistCpUtils.java:144)
  at 
org.apache.hadoop.tools.SimpleCopyListing.writeToFileListing(SimpleCopyListing.java:598)
  at 
org.apache.hadoop.tools.SimpleCopyListing.writeToFileListingRoot(SimpleCopyListing.java:583)
  at 
org.apache.hadoop.tools.SimpleCopyListing.doBuildListing(SimpleCopyListing.java:313)
  at 
org.apache.hadoop.tools.SimpleCopyListing.doBuildListing(SimpleCopyListing.java:174)
  at org.apache.hadoop.tools.CopyListing.buildListing(CopyListing.java:86)
  at 
org.apache.hadoop.tools.GlobbedCopyListing.doBuildListing(GlobbedCopyListing.java:90)
  at org.apache.hadoop.tools.CopyListing.buildListing(CopyListing.java:86)
  at org.apache.hadoop.tools.DistCp.createInputFileListing(DistCp.java:365)
  at org.apache.hadoop.tools.DistCp.execute(DistCp.java:171)
  at org.apache.hadoop.tools.DistCp.run(DistCp.java:122)
  at org.apache.hadoop.util.ToolRunner.run(ToolRunner.java:70)
  at org.apache.hadoop.tools.DistCp.main(DistCp.java:429)
{code}

Relevant code:
{code}
  private Path computeSourceRootPath(FileStatus sourceStatus,
                                     DistCpOptions options) throws IOException {

    Path target = options.getTargetPath();
    FileSystem targetFS = target.getFileSystem(getConf());
    final boolean targetPathExists = options.getTargetPathExists();

    boolean solitaryFile = options.getSourcePaths().size() == 1
                                                && !sourceStatus.isDirectory();

    if (solitaryFile) {
      if (targetFS.isFile(target) || !targetPathExists) {
        return sourceStatus.getPath();
      } else {
        return sourceStatus.getPath().getParent();
      }
    } else {
      boolean specialHandling = (options.getSourcePaths().size() == 1 && 
!targetPathExists) ||
          options.shouldSyncFolder() || options.shouldOverwrite();

      return specialHandling && sourceStatus.isDirectory() ? 
sourceStatus.getPath() :
          sourceStatus.getPath().getParent();
    }
  }
{code}

We can see that it could return NULL at the end when doing 
{{sourceStatus.getPath().getParent()}}




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