[jira] [Created] (HADOOP-18904) get local file system fails with a casting error

["ConfX (Jira)" <ji...@apache.org>]

ConfX created HADOOP-18904:
------------------------------

             Summary: get local file system fails with a casting error
                 Key: HADOOP-18904
                 URL: https://issues.apache.org/jira/browse/HADOOP-18904
             Project: Hadoop Common
          Issue Type: Bug
            Reporter: ConfX


h2. What happened

After setting {{{}fs.file.impl=org.apache.hadoop.fs.RawLocalFileSystem{}}}, trying to acquire local file system using the {{getLocal}} in {{org.apache.hadoop.fs}} fails with {{java.lang.ClassCastException}}
h2. Where's the bug

In the function {{getLocal}} of {{FileSystem}} in HCommon:
{code:java}
  public static LocalFileSystem getLocal(Configuration conf)
    throws IOException {
    return (LocalFileSystem)get(LocalFileSystem.NAME, conf);
  } {code}
the returned file system is directly cast to LocalFileSystem without checking. If the user set the implementation of the local filesystem to be Raw rather than Checksum, this type cast would fail.
h2. How to reproduce
 # Set {{fs.file.impl=org.apache.hadoop.fs.RawLocalFileSystem}}
 # Run the following test in HBase: {{org.apache.hadoop.hbase.TestHBaseTestingUtility#testMiniDFSCluster}}
and the following exception should be observed:

{code:java}
java.lang.ClassCastException: class org.apache.hadoop.fs.RawLocalFileSystem cannot be cast to class org.apache.hadoop.fs.LocalFileSystem (org.apache.hadoop.fs.RawLocalFileSystem and org.apache.hadoop.fs.LocalFileSystem are in unnamed module of loader 'app')
	at org.apache.hadoop.fs.FileSystem.getLocal(FileSystem.java:441)
	at org.apache.hadoop.hbase.HBaseTestingUtility.getNewDataTestDirOnTestFS(HBaseTestingUtility.java:550)
...{code}
Or simply set the configuration parameter and call the method using a {{Configuration}} object and the exception would be triggered.



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