HADOOP-9527. Add symlink support to LocalFileSystem on Windows. Contributed by Arpit Agarwal.

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/trunk@1511118 13f79535-47bb-0310-9956-ffa450edef68

hadoop-common-project/hadoop-common/CHANGES.txt

@@ -347,6 +347,9 @@ Release 2.1.1-beta - UNRELEASED
     HADOOP-9806 PortmapInterface should check if the procedure is out-of-range
     (brandonli)
 
+    HADOOP-9527. Add symlink support to LocalFileSystem on Windows.
+    (Arpit Agarwal via cnauroth)
+
 Release 2.1.0-beta - 2013-08-06
 
   INCOMPATIBLE CHANGES

hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/fs/FileUtil.java

@@ -142,7 +142,28 @@ public static boolean fullyDelete(final File dir, boolean tryGrantPermissions) {
     }
     return deleteImpl(dir, true);
   }
-  
+
+  /**
+   * Returns the target of the given symlink. Returns the empty string if
+   * the given path does not refer to a symlink or there is an error
+   * accessing the symlink.
+   * @param f File representing the symbolic link.
+   * @return The target of the symbolic link, empty string on error or if not
+   *         a symlink.
+   */
+  public static String readLink(File f) {
+    /* NB: Use readSymbolicLink in java.nio.file.Path once available. Could
+     * use getCanonicalPath in File to get the target of the symlink but that
+     * does not indicate if the given path refers to a symlink.
+     */
+    try {
+      return Shell.execCommand(
+          Shell.getReadlinkCommand(f.toString())).trim();
+    } catch (IOException x) {
+      return "";
+    }
+  }
+
   /*
    * Pure-Java implementation of "chmod +rwx f".
    */
@@ -737,15 +758,18 @@ public static class HardLink extends org.apache.hadoop.fs.HardLink {
    * On Windows, when symlink creation fails due to security
    * setting, we will log a warning. The return code in this
    * case is 2.
+   *
    * @param target the target for symlink 
    * @param linkname the symlink
-   * @return value returned by the command
+   * @return 0 on success
    */
   public static int symLink(String target, String linkname) throws IOException{
     // Run the input paths through Java's File so that they are converted to the
     // native OS form
-    File targetFile = new File(target);
-    File linkFile = new File(linkname);
+    File targetFile = new File(
+        Path.getPathWithoutSchemeAndAuthority(new Path(target)).toString());
+    File linkFile = new File(
+        Path.getPathWithoutSchemeAndAuthority(new Path(linkname)).toString());
 
     // If not on Java7+, copy a file instead of creating a symlink since
     // Java6 has close to no support for symlinks on Windows. Specifically
@@ -757,9 +781,16 @@ public static int symLink(String target, String linkname) throws IOException{
     // is symlinked under userlogs and userlogs are generated afterwards).
     if (Shell.WINDOWS && !Shell.isJava7OrAbove() && targetFile.isFile()) {
       try {
-        LOG.info("FileUtil#symlink: On Java6, copying file instead "
-            + linkname + " -> " + target);
-        org.apache.commons.io.FileUtils.copyFile(targetFile, linkFile);
+        LOG.warn("FileUtil#symlink: On Windows+Java6, copying file instead " +
+            "of creating a symlink. Copying " + target + " -> " + linkname);
+
+        if (!linkFile.getParentFile().exists()) {
+          LOG.warn("Parent directory " + linkFile.getParent() +
+              " does not exist.");
+          return 1;
+        } else {
+          org.apache.commons.io.FileUtils.copyFile(targetFile, linkFile);
+        }
       } catch (IOException ex) {
         LOG.warn("FileUtil#symlink failed to copy the file with error: "
             + ex.getMessage());
@@ -769,10 +800,23 @@ public static int symLink(String target, String linkname) throws IOException{
       return 0;
     }
 
-    String[] cmd = Shell.getSymlinkCommand(targetFile.getPath(),
-        linkFile.getPath());
-    ShellCommandExecutor shExec = new ShellCommandExecutor(cmd);
+    String[] cmd = Shell.getSymlinkCommand(
+        targetFile.toString(),
+        linkFile.toString());
+
+    ShellCommandExecutor shExec;
     try {
+      if (Shell.WINDOWS &&
+          linkFile.getParentFile() != null &&
+          !new Path(target).isAbsolute()) {
+        // Relative links on Windows must be resolvable at the time of
+        // creation. To ensure this we run the shell command in the directory
+        // of the link.
+        //
+        shExec = new ShellCommandExecutor(cmd, linkFile.getParentFile());
+      } else {
+        shExec = new ShellCommandExecutor(cmd);
+      }
       shExec.execute();
     } catch (Shell.ExitCodeException ec) {
       int returnVal = ec.getExitCode();
@@ -795,7 +839,7 @@ public static int symLink(String target, String linkname) throws IOException{
     }
     return shExec.getExitCode();
   }
-  
+
   /**
    * Change the permissions on a filename.
    * @param filename the name of the file to change

hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/fs/RawLocalFileSystem.java

@@ -682,31 +682,13 @@ public void createSymlink(Path target, Path link, boolean createParent)
     if (createParent) {
       mkdirs(link.getParent());
     }
-    // NB: Use createSymbolicLink in java.nio.file.Path once available
-    try {
-      Shell.execCommand(Shell.getSymlinkCommand(
-        Path.getPathWithoutSchemeAndAuthority(target).toString(),
-        Path.getPathWithoutSchemeAndAuthority(makeAbsolute(link)).toString()));
-    } catch (IOException x) {
-      throw new IOException("Unable to create symlink: "+x.getMessage());
-    }
-  }
 
-  /**
-   * Returns the target of the given symlink. Returns the empty string if
-   * the given path does not refer to a symlink or there is an error
-   * accessing the symlink.
-   */
-  private String readLink(Path p) {
-    /* NB: Use readSymbolicLink in java.nio.file.Path once available. Could
-     * use getCanonicalPath in File to get the target of the symlink but that
-     * does not indicate if the given path refers to a symlink.
-     */
-    try {
-      final String path = p.toUri().getPath();
-      return Shell.execCommand(Shell.READ_LINK_COMMAND, path).trim();
-    } catch (IOException x) {
-      return "";
+    // NB: Use createSymbolicLink in java.nio.file.Path once available
+    int result = FileUtil.symLink(target.toString(),
+        makeAbsolute(link).toString());
+    if (result != 0) {
+      throw new IOException("Error " + result + " creating symlink " +
+          link + " to " + target);
     }
   }
 
@@ -729,7 +711,7 @@ public FileStatus getFileLinkStatus(final Path f) throws IOException {
   }
 
   private FileStatus getFileLinkStatusInternal(final Path f) throws IOException {
-    String target = readLink(f);
+    String target = FileUtil.readLink(new File(f.toString()));
 
     try {
       FileStatus fs = getFileStatus(f);

hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/fs/local/RawLocalFs.java

@@ -17,6 +17,7 @@
  */
 package org.apache.hadoop.fs.local;
 
+import java.io.File;
 import java.io.FileNotFoundException;
 import java.io.IOException;
 import java.net.URI;
@@ -28,12 +29,12 @@
 import org.apache.hadoop.fs.AbstractFileSystem;
 import org.apache.hadoop.fs.DelegateToFileSystem;
 import org.apache.hadoop.fs.FileStatus;
+import org.apache.hadoop.fs.FileUtil;
 import org.apache.hadoop.fs.FsConstants;
 import org.apache.hadoop.fs.FsServerDefaults;
 import org.apache.hadoop.fs.Path;
 import org.apache.hadoop.fs.RawLocalFileSystem;
 import org.apache.hadoop.fs.permission.FsPermission;
-import org.apache.hadoop.util.Shell;
 
 /**
  * The RawLocalFs implementation of AbstractFileSystem.
@@ -75,47 +76,29 @@ public FsServerDefaults getServerDefaults() throws IOException {
   @Override
   public boolean supportsSymlinks() {
     return true;
-  }  
-  
+  }
+
   @Override
-  public void createSymlink(Path target, Path link, boolean createParent) 
+  public void createSymlink(Path target, Path link, boolean createParent)
       throws IOException {
     final String targetScheme = target.toUri().getScheme();
     if (targetScheme != null && !"file".equals(targetScheme)) {
       throw new IOException("Unable to create symlink to non-local file "+
-                            "system: "+target.toString());
+          "system: "+target.toString());
     }
+
     if (createParent) {
       mkdir(link.getParent(), FsPermission.getDirDefault(), true);
     }
+
     // NB: Use createSymbolicLink in java.nio.file.Path once available
-    try {
-      Shell.execCommand(Shell.getSymlinkCommand(
-        Path.getPathWithoutSchemeAndAuthority(target).toString(),
-        Path.getPathWithoutSchemeAndAuthority(link).toString()));
-    } catch (IOException x) {
-      throw new IOException("Unable to create symlink: "+x.getMessage());
+    int result = FileUtil.symLink(target.toString(), link.toString());
+    if (result != 0) {
+      throw new IOException("Error " + result + " creating symlink " +
+          link + " to " + target);
     }
   }
 
-  /** 
-   * Returns the target of the given symlink. Returns the empty string if  
-   * the given path does not refer to a symlink or there is an error 
-   * acessing the symlink.
-   */
-  private String readLink(Path p) {
-    /* NB: Use readSymbolicLink in java.nio.file.Path once available. Could
-     * use getCanonicalPath in File to get the target of the symlink but that 
-     * does not indicate if the given path refers to a symlink.
-     */
-    try {
-      final String path = p.toUri().getPath();
-      return Shell.execCommand(Shell.READ_LINK_COMMAND, path).trim(); 
-    } catch (IOException x) {
-      return "";
-    }
-  }
-  
   /**
    * Return a FileStatus representing the given path. If the path refers 
    * to a symlink return a FileStatus representing the link rather than
@@ -123,7 +106,7 @@ private String readLink(Path p) {
    */
   @Override
   public FileStatus getFileLinkStatus(final Path f) throws IOException {
-    String target = readLink(f);
+    String target = FileUtil.readLink(new File(f.toString()));
     try {
       FileStatus fs = getFileStatus(f);
       // If f refers to a regular file or directory      

hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/util/Shell.java

@@ -123,6 +123,12 @@ public static String[] getSymlinkCommand(String target, String link) {
                    : new String[] { "ln", "-s", target, link };
   }
 
+  /** Return a command to read the target of the a symbolic link*/
+  public static String[] getReadlinkCommand(String link) {
+    return WINDOWS ? new String[] { WINUTILS, "readlink", link }
+        : new String[] { "readlink", link };
+  }
+
   /** Return a command for determining if process with specified pid is alive. */
   public static String[] getCheckProcessIsAliveCommand(String pid) {
     return Shell.WINDOWS ?

hadoop-common-project/hadoop-common/src/test/java/org/apache/hadoop/fs/FSTestWrapper.java

@@ -71,7 +71,8 @@ public Path getTestRootPath(String pathString) {
 
   public String getAbsoluteTestRootDir() throws IOException {
     if (absTestRootDir == null) {
-      if (testRootDir.startsWith("/")) {
+      Path testRootPath = new Path(testRootDir);
+      if (testRootPath.isAbsolute()) {
         absTestRootDir = testRootDir;
       } else {
         absTestRootDir = getWorkingDirectory().toString() + "/"

hadoop-common-project/hadoop-common/src/test/java/org/apache/hadoop/fs/SymlinkBaseTest.java

@@ -20,13 +20,10 @@
 import java.io.*;
 import java.net.URI;
 import java.util.EnumSet;
-import org.apache.hadoop.fs.FileContext;
+
 import org.apache.hadoop.fs.Options.CreateOpts;
 import org.apache.hadoop.fs.Options.Rename;
 import org.apache.hadoop.fs.permission.FsPermission;
-import org.apache.hadoop.fs.CreateFlag;
-import org.apache.hadoop.fs.Path;
-import org.apache.hadoop.fs.FSDataOutputStream;
 import org.apache.hadoop.test.GenericTestUtils;
 
 import static org.junit.Assert.*;
@@ -51,6 +48,13 @@ public abstract class SymlinkBaseTest {
   abstract protected String testBaseDir2() throws IOException;
   abstract protected URI testURI();
 
+  // Returns true if the filesystem is emulating symlink support. Certain
+  // checks will be bypassed if that is the case.
+  //
+  protected boolean emulatingSymlinksOnWindows() {
+    return false;
+  }
+
   protected IOException unwrapException(IOException e) {
     return e;
   }
@@ -156,8 +160,11 @@ public void testCreateLinkCanCreateParent() throws IOException {
   @Test(timeout=10000)
   /** Try to create a directory given a path that refers to a symlink */
   public void testMkdirExistingLink() throws IOException {
+    Path file = new Path(testBaseDir1() + "/targetFile");
+    createAndWriteFile(file);
+
     Path dir  = new Path(testBaseDir1()+"/link");
-    wrapper.createSymlink(new Path("/doesNotExist"), dir, false);
+    wrapper.createSymlink(file, dir, false);
     try {
       wrapper.mkdir(dir, FileContext.DEFAULT_PERM, false);
       fail("Created a dir where a symlink exists");
@@ -224,6 +231,7 @@ public void testOpenResolvesLinks() throws IOException {
   @Test(timeout=10000)
   /** Stat a link to a file */
   public void testStatLinkToFile() throws IOException {
+    assumeTrue(!emulatingSymlinksOnWindows());
     Path file = new Path(testBaseDir1()+"/file");
     Path linkToFile = new Path(testBaseDir1()+"/linkToFile");
     createAndWriteFile(file);
@@ -232,8 +240,7 @@ public void testStatLinkToFile() throws IOException {
     assertTrue(wrapper.isSymlink(linkToFile));
     assertTrue(wrapper.isFile(linkToFile));
     assertFalse(wrapper.isDir(linkToFile));
-    assertEquals(file.toUri().getPath(),
-                 wrapper.getLinkTarget(linkToFile).toString());
+    assertEquals(file, wrapper.getLinkTarget(linkToFile));
     // The local file system does not fully resolve the link
     // when obtaining the file status
     if (!"file".equals(getScheme())) {
@@ -277,8 +284,7 @@ public void testStatLinkToDir() throws IOException {
     assertFalse(wrapper.isFile(linkToDir));
     assertTrue(wrapper.isDir(linkToDir));
 
-    assertEquals(dir.toUri().getPath(),
-                 wrapper.getLinkTarget(linkToDir).toString());
+    assertEquals(dir, wrapper.getLinkTarget(linkToDir));
   }
 
   @Test(timeout=10000)
@@ -351,6 +357,12 @@ public void testRecursiveLinks() throws IOException {
   /* Assert that the given link to a file behaves as expected. */
   private void checkLink(Path linkAbs, Path expectedTarget, Path targetQual)
       throws IOException {
+
+    // If we are emulating symlinks then many of these checks will fail
+    // so we skip them.
+    //
+    assumeTrue(!emulatingSymlinksOnWindows());
+
     Path dir = new Path(testBaseDir1());
     // isFile/Directory
     assertTrue(wrapper.isFile(linkAbs));
@@ -400,7 +412,7 @@ else if (wrapper instanceof FileSystemTestWrapper) {
       failureExpected = false;
     }
     try {
-      readFile(new Path(getScheme()+"://"+testBaseDir1()+"/linkToFile"));
+      readFile(new Path(getScheme()+":///"+testBaseDir1()+"/linkToFile"));
       assertFalse(failureExpected);
     } catch (Exception e) {
       if (!failureExpected) {
@@ -646,6 +658,7 @@ public void testCreateDirViaSymlink() throws IOException {
   @Test(timeout=10000)
   /** Create symlink through a symlink */
   public void testCreateLinkViaLink() throws IOException {
+    assumeTrue(!emulatingSymlinksOnWindows());
     Path dir1        = new Path(testBaseDir1());
     Path file        = new Path(testBaseDir1(), "file");
     Path linkToDir   = new Path(testBaseDir2(), "linkToDir");
@@ -688,6 +701,7 @@ public void testListStatusUsingLink() throws IOException {
   @Test(timeout=10000)
   /** Test create symlink using the same path */
   public void testCreateLinkTwice() throws IOException {
+    assumeTrue(!emulatingSymlinksOnWindows());
     Path file = new Path(testBaseDir1(), "file");
     Path link = new Path(testBaseDir1(), "linkToFile");
     createAndWriteFile(file);
@@ -783,7 +797,7 @@ public void testCreateLinkToDotDot() throws IOException {
     Path linkToDir   = new Path(testBaseDir2(), "linkToDir");
     Path fileViaLink = new Path(linkToDir,      "test/file");
     // Symlink to .. is not a problem since the .. is squashed early
-    assertEquals(testBaseDir1(), dotDot.toString());
+    assertEquals(new Path(testBaseDir1()), dotDot);
     createAndWriteFile(file);
     wrapper.createSymlink(dotDot, linkToDir, false);
     readFile(fileViaLink);
@@ -876,7 +890,8 @@ public void testRenameSymlinkViaSymlink() throws IOException {
     assertFalse(wrapper.exists(linkViaLink));
     // Check that we didn't rename the link target
     assertTrue(wrapper.exists(file));
-    assertTrue(wrapper.getFileLinkStatus(linkNewViaLink).isSymlink());
+    assertTrue(wrapper.getFileLinkStatus(linkNewViaLink).isSymlink() ||
+        emulatingSymlinksOnWindows());
     readFile(linkNewViaLink);
   }
 
@@ -1014,7 +1029,8 @@ public void testRenameSymlinkNonExistantDest() throws IOException {
     createAndWriteFile(file);
     wrapper.createSymlink(file, link1, false);
     wrapper.rename(link1, link2);
-    assertTrue(wrapper.getFileLinkStatus(link2).isSymlink());
+    assertTrue(wrapper.getFileLinkStatus(link2).isSymlink() ||
+        emulatingSymlinksOnWindows());
     readFile(link2);
     readFile(file);
     assertFalse(wrapper.exists(link1));
@@ -1038,8 +1054,11 @@ public void testRenameSymlinkToExistingFile() throws IOException {
     }
     wrapper.rename(link, file1, Rename.OVERWRITE);
     assertFalse(wrapper.exists(link));
-    assertTrue(wrapper.getFileLinkStatus(file1).isSymlink());
-    assertEquals(file2, wrapper.getLinkTarget(file1));
+
+    if (!emulatingSymlinksOnWindows()) {
+      assertTrue(wrapper.getFileLinkStatus(file1).isSymlink());
+      assertEquals(file2, wrapper.getLinkTarget(file1));
+    }
   }
 
   @Test(timeout=10000)
@@ -1078,16 +1097,21 @@ public void testRenameSymlinkToExistingDir() throws IOException {
   @Test(timeout=10000)
   /** Rename a symlink to itself */
   public void testRenameSymlinkToItself() throws IOException {
+    Path file = new Path(testBaseDir1(), "file");
+    createAndWriteFile(file);
+
     Path link = new Path(testBaseDir1(), "linkToFile1");
-    wrapper.createSymlink(new Path("/doestNotExist"), link, false);
+    wrapper.createSymlink(file, link, false);
     try {
       wrapper.rename(link, link);
+      fail("Failed to get expected IOException");
     } catch (IOException e) {
       assertTrue(unwrapException(e) instanceof FileAlreadyExistsException);
     }
     // Fails with overwrite as well
     try {
       wrapper.rename(link, link, Rename.OVERWRITE);
+      fail("Failed to get expected IOException");
     } catch (IOException e) {
       assertTrue(unwrapException(e) instanceof FileAlreadyExistsException);
     }
@@ -1096,6 +1120,7 @@ public void testRenameSymlinkToItself() throws IOException {
   @Test(timeout=10000)
   /** Rename a symlink */
   public void testRenameSymlink() throws IOException {
+    assumeTrue(!emulatingSymlinksOnWindows());
     Path file  = new Path(testBaseDir1(), "file");
     Path link1 = new Path(testBaseDir1(), "linkToFile1");
     Path link2 = new Path(testBaseDir1(), "linkToFile2");
@@ -1193,6 +1218,7 @@ public void testRenameSymlinkToDirItLinksTo() throws IOException {
   @Test(timeout=10000)
   /** Test rename the symlink's target */
   public void testRenameLinkTarget() throws IOException {
+    assumeTrue(!emulatingSymlinksOnWindows());
     Path file    = new Path(testBaseDir1(), "file");
     Path fileNew = new Path(testBaseDir1(), "fileNew");
     Path link    = new Path(testBaseDir1(), "linkToFile");

hadoop-common-project/hadoop-common/src/test/java/org/apache/hadoop/fs/TestSymlinkLocalFS.java

@@ -30,6 +30,7 @@
 import java.net.URISyntaxException;
 
 import org.apache.hadoop.fs.permission.FsPermission;
+import org.apache.hadoop.util.Shell;
 import org.junit.Test;
 
 /**
@@ -61,6 +62,16 @@ protected URI testURI() {
     }
   }
 
+  @Override
+  protected boolean emulatingSymlinksOnWindows() {
+    // Java 6 on Windows has very poor symlink support. Specifically
+    // Specifically File#length and File#renameTo do not work as expected.
+    // (see HADOOP-9061 for additional details)
+    // Hence some symlink tests will be skipped.
+    //
+    return (Shell.WINDOWS && !Shell.isJava7OrAbove());
+  }
+
   @Override
   public void testCreateDanglingLink() throws IOException {
     // Dangling symlinks are not supported on Windows local file system.
@@ -171,6 +182,7 @@ public void testDanglingLink() throws IOException {
    * file scheme (eg file://host/tmp/test).
    */  
   public void testGetLinkStatusPartQualTarget() throws IOException {
+    assumeTrue(!emulatingSymlinksOnWindows());
     Path fileAbs  = new Path(testBaseDir1()+"/file");
     Path fileQual = new Path(testURI().toString(), fileAbs);
     Path dir      = new Path(testBaseDir1());
@@ -205,4 +217,14 @@ public void testGetLinkStatusPartQualTarget() throws IOException {
       // Excpected.
     }
   }
+
+  /** Test create symlink to . */
+  @Override
+  public void testCreateLinkToDot() throws IOException {
+    try {
+      super.testCreateLinkToDot();
+    } catch (IllegalArgumentException iae) {
+      // Expected.
+    }
+  }
 }

hadoop-common-project/hadoop-common/src/test/java/org/apache/hadoop/fs/TestSymlinkLocalFSFileContext.java

@@ -17,8 +17,13 @@
  */
 package org.apache.hadoop.fs;
 
+import org.apache.hadoop.util.Shell;
 import org.junit.BeforeClass;
 
+import java.io.IOException;
+
+import static org.junit.Assume.assumeTrue;
+
 public class TestSymlinkLocalFSFileContext extends TestSymlinkLocalFS {
 
   @BeforeClass
@@ -27,4 +32,9 @@ public static void testSetup() throws Exception {
     wrapper = new FileContextTestWrapper(context);
   }
 
+  @Override
+  public void testRenameFileWithDestParentSymlink() throws IOException {
+    assumeTrue(!Shell.WINDOWS);
+    super.testRenameFileWithDestParentSymlink();
+  }
 }

hadoop-common-project/hadoop-common/src/test/java/org/apache/hadoop/fs/TestSymlinkLocalFSFileSystem.java

@@ -17,13 +17,20 @@
  */
 package org.apache.hadoop.fs;
 
+import java.io.FileNotFoundException;
 import java.io.IOException;
 
 import org.apache.hadoop.conf.Configuration;
+import org.apache.hadoop.fs.Options.Rename;
+import org.apache.hadoop.util.Shell;
 import org.junit.BeforeClass;
 import org.junit.Ignore;
 import org.junit.Test;
 
+import static org.junit.Assert.assertTrue;
+import static org.junit.Assert.fail;
+import static org.junit.Assume.assumeTrue;
+
 public class TestSymlinkLocalFSFileSystem extends TestSymlinkLocalFS {
 
   @BeforeClass
@@ -54,4 +61,36 @@ public void testCreateFileDirExistingLink() throws IOException {}
   @Override
   @Test(timeout=1000)
   public void testAccessFileViaInterSymlinkAbsTarget() throws IOException {}
+
+  @Override
+  public void testRenameFileWithDestParentSymlink() throws IOException {
+    assumeTrue(!Shell.WINDOWS);
+    super.testRenameFileWithDestParentSymlink();
+  }
+
+  @Override
+  @Test(timeout=10000)
+  /** Rename a symlink to itself */
+  public void testRenameSymlinkToItself() throws IOException {
+    Path file = new Path(testBaseDir1(), "file");
+    createAndWriteFile(file);
+
+    Path link = new Path(testBaseDir1(), "linkToFile1");
+    wrapper.createSymlink(file, link, false);
+    try {
+      wrapper.rename(link, link);
+      fail("Failed to get expected IOException");
+    } catch (IOException e) {
+      assertTrue(unwrapException(e) instanceof FileAlreadyExistsException);
+    }
+    // Fails with overwrite as well
+    try {
+      wrapper.rename(link, link, Rename.OVERWRITE);
+      fail("Failed to get expected IOException");
+    } catch (IOException e) {
+      // Todo: Fix this test when HADOOP-9819 is fixed.
+      assertTrue(unwrapException(e) instanceof FileAlreadyExistsException ||
+                 unwrapException(e) instanceof FileNotFoundException);
+    }
+  }
 }