HADOOP-10020. Disable symlinks temporarily (branch-2.1-beta only change). Contributed by Sanjay Radia.

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2.1-beta@1529712 13f79535-47bb-0310-9956-ffa450edef68

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

@@ -19,6 +19,9 @@ Release 2.1.2 - UNRELEASED
 
   INCOMPATIBLE CHANGES
 
+    HADOOP-10020. Disable symlinks temporarily (branch-2.1-beta only change)
+    (sanjay via suresh)
+
   NEW FEATURES
 
     HDFS-4817.  Make HDFS advisory caching configurable on a per-file basis.

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

@@ -1339,11 +1339,15 @@ public final class FileContext {
    *           <code>target</code> or <code>link</code> is not supported
    * @throws IOException If an I/O error occurred
    */
+  @SuppressWarnings("deprecation")
   public void createSymlink(final Path target, final Path link,
       final boolean createParent) throws AccessControlException,
       FileAlreadyExistsException, FileNotFoundException,
       ParentNotDirectoryException, UnsupportedFileSystemException, 
       IOException { 
+    if (!FileSystem.isSymlinksEnabled()) {
+      throw new UnsupportedOperationException("Symlinks not supported");
+    }
     final Path nonRelLink = fixRelativePart(link);
     new FSLinkResolver<Void>() {
       @Override

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

@@ -2807,4 +2807,24 @@ public abstract class FileSystem extends Configured implements Closeable {
                          ": " + pair.getValue());
     }
   }
+  
+  // Symlinks are temporarily disabled - see Hadoop-10020
+  private static boolean symlinkEnabled = false;
+  private static Configuration conf = null;
+  
+  @Deprecated
+  @VisibleForTesting
+  public static boolean isSymlinksEnabled() {
+    if (conf == null) {
+      Configuration conf = new Configuration();
+      symlinkEnabled = conf.getBoolean("test.SymlinkEnabledForTesting", false); 
+    }
+    return symlinkEnabled;
+  }
+  
+  @Deprecated
+  @VisibleForTesting
+  public static void enableSymlinks() {
+    symlinkEnabled = true;
+  }
 }

hadoop-common-project/hadoop-common/src/test/resources/core-site.xml

@@ -78,4 +78,9 @@
   <name>nfs3.mountd.port</name>
   <value>4272</value>
 </property>
+
+<property>
+  <name>test.SymlinkEnabledForTesting</name>
+  <value>true</value>
+</property>
 </configuration>

hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/DistributedFileSystem.java

@@ -1118,12 +1118,16 @@ public class DistributedFileSystem extends FileSystem {
     }.resolve(this, absF);
   }
 
+  @SuppressWarnings("deprecation")
   @Override
   public void createSymlink(final Path target, final Path link,
       final boolean createParent) throws AccessControlException,
       FileAlreadyExistsException, FileNotFoundException,
       ParentNotDirectoryException, UnsupportedFileSystemException, 
       IOException {
+    if (!FileSystem.isSymlinksEnabled()) {
+      throw new UnsupportedOperationException("Symlinks not supported");
+    }
     statistics.incrementWriteOps(1);
     final Path absF = fixRelativePart(link);
     new FileSystemLinkResolver<Void>() {

hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/FSEditLogLoader.java

@@ -32,6 +32,7 @@ import org.apache.commons.logging.Log;
 import org.apache.commons.logging.LogFactory;
 import org.apache.hadoop.classification.InterfaceAudience;
 import org.apache.hadoop.classification.InterfaceStability;
+import org.apache.hadoop.fs.FileSystem;
 import org.apache.hadoop.hdfs.protocol.Block;
 import org.apache.hadoop.hdfs.protocol.HdfsConstants;
 import org.apache.hadoop.hdfs.protocol.HdfsFileStatus;
@@ -501,6 +502,9 @@ public class FSEditLogLoader {
       break;
     }
     case OP_SYMLINK: {
+      if (!FileSystem.isSymlinksEnabled()) {
+        throw new IOException("Symlinks not supported - please remove symlink before upgrading to this version of HDFS");
+      }
       SymlinkOp symlinkOp = (SymlinkOp)op;
       inodeId = getAndUpdateLastInodeId(symlinkOp.inodeId, logVersion,
           lastInodeId);

hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/FSImageFormat.java

@@ -40,6 +40,7 @@ import org.apache.hadoop.HadoopIllegalArgumentException;
 import org.apache.hadoop.classification.InterfaceAudience;
 import org.apache.hadoop.classification.InterfaceStability;
 import org.apache.hadoop.conf.Configuration;
+import org.apache.hadoop.fs.FileSystem;
 import org.apache.hadoop.fs.Path;
 import org.apache.hadoop.fs.PathIsNotDirectoryException;
 import org.apache.hadoop.fs.UnresolvedLinkException;
@@ -627,6 +628,7 @@ public class FSImageFormat {
    * @param counter Counter to increment for namenode startup progress
    * @return an inode
    */
+  @SuppressWarnings("deprecation")
   INode loadINode(final byte[] localName, boolean isSnapshotINode,
       DataInput in, Counter counter) throws IOException {
     final int imgVersion = getLayoutVersion();
@@ -724,6 +726,9 @@ public class FSImageFormat {
           : dir;
     } else if (numBlocks == -2) {
       //symlink
+      if (!FileSystem.isSymlinksEnabled()) {
+        throw new IOException("Symlinks not supported - please remove symlink before upgrading to this version of HDFS");
+      }
 
       final String symlink = Text.readString(in);
       final PermissionStatus permissions = PermissionStatus.read(in);

hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/FSNamesystem.java

@@ -125,6 +125,7 @@ import org.apache.hadoop.fs.ContentSummary;
 import org.apache.hadoop.fs.CreateFlag;
 import org.apache.hadoop.fs.FileAlreadyExistsException;
 import org.apache.hadoop.fs.FileStatus;
+import org.apache.hadoop.fs.FileSystem;
 import org.apache.hadoop.fs.FsServerDefaults;
 import org.apache.hadoop.fs.InvalidPathException;
 import org.apache.hadoop.fs.Options;
@@ -1769,9 +1770,13 @@ public class FSNamesystem implements Namesystem, FSClusterStats,
   /**
    * Create a symbolic link.
    */
+  @SuppressWarnings("deprecation")
   void createSymlink(String target, String link,
       PermissionStatus dirPerms, boolean createParent) 
       throws IOException, UnresolvedLinkException {
+    if (!FileSystem.isSymlinksEnabled()) {
+      throw new UnsupportedOperationException("Symlinks not supported");
+    }
     if (!DFSUtil.isValidName(link)) {
       throw new InvalidPathException("Invalid link name: " + link);
     }

hadoop-hdfs-project/hadoop-hdfs/src/test/resources/hdfs-site.xml

@@ -31,4 +31,8 @@
     <value>0</value>
   </property>
 
+ <property>
+   <name>test.SymlinkEnabledForTesting</name>
+   <value>true</value>
+ </property>
 </configuration>