HDFS-7528. Consolidate symlink-related implementation into a single class. Contributed by Haohui Mai.

hadoop-hdfs-project/hadoop-hdfs/CHANGES.txt

@@ -205,6 +205,9 @@ Release 2.7.0 - UNRELEASED
     HDFS-7536. Remove unused CryptoCodec in org.apache.hadoop.fs.Hdfs.
     (Yi Liu via wheat9)
 
+    HDFS-7528. Consolidate symlink-related implementation into a single class.
+    (wheat9)
+
   OPTIMIZATIONS
 
     HDFS-7454. Reduce memory footprint for AclEntries in NameNode.

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

@@ -0,0 +1,128 @@
+/**
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.apache.hadoop.hdfs.server.namenode;
+
+import org.apache.hadoop.fs.InvalidPathException;
+import org.apache.hadoop.fs.UnresolvedLinkException;
+import org.apache.hadoop.fs.permission.FsAction;
+import org.apache.hadoop.fs.permission.FsPermission;
+import org.apache.hadoop.fs.permission.PermissionStatus;
+import org.apache.hadoop.hdfs.DFSUtil;
+import org.apache.hadoop.hdfs.protocol.HdfsFileStatus;
+import org.apache.hadoop.hdfs.protocol.QuotaExceededException;
+
+import java.io.IOException;
+
+import static org.apache.hadoop.util.Time.now;
+
+class FSDirSymlinkOp {
+
+  static HdfsFileStatus createSymlinkInt(
+      FSNamesystem fsn, String target, final String linkArg,
+      PermissionStatus dirPerms, boolean createParent, boolean logRetryCache)
+      throws IOException {
+    FSDirectory fsd = fsn.getFSDirectory();
+    String link = linkArg;
+    if (!DFSUtil.isValidName(link)) {
+      throw new InvalidPathException("Invalid link name: " + link);
+    }
+    if (FSDirectory.isReservedName(target) || target.isEmpty()) {
+      throw new InvalidPathException("Invalid target name: " + target);
+    }
+
+    if (NameNode.stateChangeLog.isDebugEnabled()) {
+      NameNode.stateChangeLog.debug("DIR* NameSystem.createSymlink: target="
+          + target + " link=" + link);
+    }
+
+    FSPermissionChecker pc = fsn.getPermissionChecker();
+    byte[][] pathComponents = FSDirectory.getPathComponentsForReservedPath(link);
+    fsd.writeLock();
+    try {
+      link = fsd.resolvePath(pc, link, pathComponents);
+      final INodesInPath iip = fsd.getINodesInPath4Write(link, false);
+      if (!createParent) {
+        fsd.verifyParentDir(iip, link);
+      }
+      if (!fsd.isValidToCreate(link, iip)) {
+        throw new IOException(
+            "failed to create link " + link +
+                " either because the filename is invalid or the file exists");
+      }
+      if (fsd.isPermissionEnabled()) {
+        fsd.checkAncestorAccess(pc, iip, FsAction.WRITE);
+      }
+      // validate that we have enough inodes.
+      fsn.checkFsObjectLimit();
+
+      // add symbolic link to namespace
+      addSymlink(fsd, link, iip, target, dirPerms, createParent, logRetryCache);
+    } finally {
+      fsd.writeUnlock();
+    }
+    NameNode.getNameNodeMetrics().incrCreateSymlinkOps();
+    return fsd.getAuditFileInfo(link, false);
+  }
+
+  static INodeSymlink unprotectedAddSymlink(
+      FSDirectory fsd, INodesInPath iip, long id, String target, long mtime,
+      long atime, PermissionStatus perm)
+      throws UnresolvedLinkException, QuotaExceededException {
+    assert fsd.hasWriteLock();
+    final INodeSymlink symlink = new INodeSymlink(id, null, perm, mtime, atime,
+        target);
+    return fsd.addINode(iip, symlink) ? symlink : null;
+  }
+
+  /**
+   * Add the given symbolic link to the fs. Record it in the edits log.
+   */
+  private static INodeSymlink addSymlink(
+      FSDirectory fsd, String path, INodesInPath iip, String target,
+      PermissionStatus dirPerms, boolean createParent, boolean logRetryCache)
+      throws IOException {
+    final long mtime = now();
+    if (createParent) {
+      INodesInPath parentIIP = iip.getParentINodesInPath();
+      if (parentIIP == null || (parentIIP = FSDirMkdirOp.mkdirsRecursively(
+          fsd,
+          parentIIP, dirPerms, true, mtime)) == null) {
+        return null;
+      } else {
+        iip = INodesInPath.append(parentIIP, null, iip.getLastLocalName());
+      }
+    }
+    final String userName = dirPerms.getUserName();
+    long id = fsd.allocateNewInodeId();
+    PermissionStatus perm = new PermissionStatus(
+        userName, null, FsPermission.getDefault());
+    INodeSymlink newNode =
+        unprotectedAddSymlink(fsd, iip, id, target, mtime, mtime, perm);
+    if (newNode == null) {
+      NameNode.stateChangeLog.info("addSymlink: failed to add " + path);
+      return null;
+    }
+    fsd.getEditLog().logSymlink(path, target, mtime, mtime, newNode,
+        logRetryCache);
+
+    if(NameNode.stateChangeLog.isDebugEnabled()) {
+      NameNode.stateChangeLog.debug("addSymlink: " + path + " is added");
+    }
+    return newNode;
+  }
+}

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

@@ -860,7 +860,7 @@ public class FSDirectory implements Closeable {
    * @param iip the INodesInPath instance containing all the ancestral INodes
    * @throws QuotaExceededException is thrown if it violates quota limit
    */
-  private boolean addINode(INodesInPath iip, INode child)
+  boolean addINode(INodesInPath iip, INode child)
       throws QuotaExceededException, UnresolvedLinkException {
     child.setLocalName(iip.getLastLocalName());
     cacheName(child);
@@ -1192,29 +1192,6 @@ public class FSDirectory implements Closeable {
     }
   }
 
-  /**
-   * Add the specified path into the namespace.
-   */
-  INodeSymlink addSymlink(INodesInPath iip, long id, String target,
-                          long mtime, long atime, PermissionStatus perm)
-          throws UnresolvedLinkException, QuotaExceededException {
-    writeLock();
-    try {
-      return unprotectedAddSymlink(iip, id, target, mtime, atime, perm);
-    } finally {
-      writeUnlock();
-    }
-  }
-
-  INodeSymlink unprotectedAddSymlink(INodesInPath iip, long id, String target,
-      long mtime, long atime, PermissionStatus perm)
-      throws UnresolvedLinkException, QuotaExceededException {
-    assert hasWriteLock();
-    final INodeSymlink symlink = new INodeSymlink(id, null, perm, mtime, atime,
-        target);
-    return addINode(iip, symlink) ? symlink : null;
-  }
-
   boolean isInAnEZ(INodesInPath iip)
       throws UnresolvedLinkException, SnapshotAccessControlException {
     readLock();

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

@@ -361,12 +361,12 @@ public class FSEditLogLoader {
         // add to the file tree
         inodeId = getAndUpdateLastInodeId(addCloseOp.inodeId, logVersion,
             lastInodeId);
-        newFile = fsDir.unprotectedAddFile(inodeId,
-            iip, addCloseOp.permissions, addCloseOp.aclEntries,
-            addCloseOp.xAttrs,
-            replication, addCloseOp.mtime, addCloseOp.atime,
-            addCloseOp.blockSize, true, addCloseOp.clientName,
-            addCloseOp.clientMachine, addCloseOp.storagePolicyId);
+        newFile = fsDir.unprotectedAddFile(
+            inodeId, iip, addCloseOp.permissions, addCloseOp.aclEntries,
+            addCloseOp.xAttrs, replication, addCloseOp.mtime,
+            addCloseOp.atime, addCloseOp.blockSize, true,
+            addCloseOp.clientName, addCloseOp.clientMachine,
+            addCloseOp.storagePolicyId);
         iip = INodesInPath.replace(iip, iip.length() - 1, newFile);
         fsNamesys.leaseManager.addLease(addCloseOp.clientName, path);
 
@@ -591,9 +591,9 @@ public class FSEditLogLoader {
       final String path = renameReservedPathsOnUpgrade(symlinkOp.path,
           logVersion);
       final INodesInPath iip = fsDir.getINodesInPath(path, false);
-      fsDir.unprotectedAddSymlink(iip, inodeId,
-          symlinkOp.value, symlinkOp.mtime, symlinkOp.atime,
-          symlinkOp.permissionStatus);
+      FSDirSymlinkOp.unprotectedAddSymlink(fsDir, iip, inodeId, symlinkOp.value,
+                                           symlinkOp.mtime, symlinkOp.atime,
+                                           symlinkOp.permissionStatus);
       
       if (toAddRetryCache) {
         fsNamesys.addCacheEntry(symlinkOp.rpcClientId, symlinkOp.rpcCallId);

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

@@ -172,7 +172,6 @@ import org.apache.hadoop.hdfs.HAUtil;
 import org.apache.hadoop.hdfs.HdfsConfiguration;
 import org.apache.hadoop.hdfs.UnknownCryptoProtocolVersionException;
 import org.apache.hadoop.hdfs.XAttrHelper;
-import org.apache.hadoop.hdfs.protocol.AclException;
 import org.apache.hadoop.hdfs.protocol.AlreadyBeingCreatedException;
 import org.apache.hadoop.hdfs.protocol.Block;
 import org.apache.hadoop.hdfs.protocol.CacheDirectiveEntry;
@@ -1912,60 +1911,22 @@ public class FSNamesystem implements Namesystem, FSNamesystemMBean,
     if (!FileSystem.areSymlinksEnabled()) {
       throw new UnsupportedOperationException("Symlinks not supported");
     }
-    if (!DFSUtil.isValidName(link)) {
-      throw new InvalidPathException("Invalid link name: " + link);
-    }
-    if (FSDirectory.isReservedName(target)) {
-      throw new InvalidPathException("Invalid target name: " + target);
-    }
-
-    try {
-      createSymlinkInt(target, link, dirPerms, createParent, logRetryCache);
-    } catch (AccessControlException e) {
-      logAuditEvent(false, "createSymlink", link, target, null);
-      throw e;
-    }
-  }
-
-  private void createSymlinkInt(String target, final String linkArg,
-      PermissionStatus dirPerms, boolean createParent, boolean logRetryCache) 
-      throws IOException {
-    String link = linkArg;
-    if (NameNode.stateChangeLog.isDebugEnabled()) {
-      NameNode.stateChangeLog.debug("DIR* NameSystem.createSymlink: target="
-          + target + " link=" + link);
-    }
-    HdfsFileStatus resultingStat = null;
-    FSPermissionChecker pc = getPermissionChecker();
+    HdfsFileStatus auditStat = null;
     checkOperation(OperationCategory.WRITE);
-    byte[][] pathComponents = FSDirectory.getPathComponentsForReservedPath(link);
     writeLock();
     try {
       checkOperation(OperationCategory.WRITE);
       checkNameNodeSafeMode("Cannot create symlink " + link);
-      link = dir.resolvePath(pc, link, pathComponents);
-      final INodesInPath iip = dir.getINodesInPath4Write(link, false);
-      if (!createParent) {
-        dir.verifyParentDir(iip, link);
-      }
-      if (!dir.isValidToCreate(link, iip)) {
-        throw new IOException("failed to create link " + link 
-            +" either because the filename is invalid or the file exists");
-      }
-      if (isPermissionEnabled) {
-        dir.checkAncestorAccess(pc, iip, FsAction.WRITE);
-      }
-      // validate that we have enough inodes.
-      checkFsObjectLimit();
-
-      // add symbolic link to namespace
-      addSymlink(link, iip, target, dirPerms, createParent, logRetryCache);
-      resultingStat = getAuditFileInfo(link, false);
+      auditStat = FSDirSymlinkOp.createSymlinkInt(this, target, link, dirPerms,
+                                                  createParent, logRetryCache);
+    } catch (AccessControlException e) {
+      logAuditEvent(false, "createSymlink", link, target, null);
+      throw e;
     } finally {
       writeUnlock();
     }
     getEditLog().logSync();
-    logAuditEvent(true, "createSymlink", linkArg, target, resultingStat);
+    logAuditEvent(true, "createSymlink", link, target, auditStat);
   }
 
   /**
@@ -4360,43 +4321,6 @@ public class FSNamesystem implements Namesystem, FSNamesystemMBean,
     }
   }
 
-  /**
-   * Add the given symbolic link to the fs. Record it in the edits log.
-   */
-  private INodeSymlink addSymlink(String path, INodesInPath iip, String target,
-                                  PermissionStatus dirPerms,
-                                  boolean createParent, boolean logRetryCache)
-      throws UnresolvedLinkException, FileAlreadyExistsException,
-      QuotaExceededException, SnapshotAccessControlException, AclException {
-    waitForLoadingFSImage();
-
-    final long modTime = now();
-    if (createParent) {
-      INodesInPath parentIIP = iip.getParentINodesInPath();
-      if (parentIIP == null || (parentIIP = FSDirMkdirOp.mkdirsRecursively(dir,
-          parentIIP, dirPerms, true, modTime)) == null) {
-        return null;
-      } else {
-        iip = INodesInPath.append(parentIIP, null, iip.getLastLocalName());
-      }
-    }
-    final String userName = dirPerms.getUserName();
-    long id = dir.allocateNewInodeId();
-    INodeSymlink newNode = dir.addSymlink(iip, id, target, modTime, modTime,
-            new PermissionStatus(userName, null, FsPermission.getDefault()));
-    if (newNode == null) {
-      NameNode.stateChangeLog.info("addSymlink: failed to add " + path);
-      return null;
-    }
-    getEditLog().logSymlink(path, target, modTime, modTime, newNode,
-        logRetryCache);
-
-    if(NameNode.stateChangeLog.isDebugEnabled()) {
-      NameNode.stateChangeLog.debug("addSymlink: " + path + " is added");
-    }
-    return newNode;
-  }
-
   /**
    * Periodically calls hasAvailableResources of NameNodeResourceChecker, and if
    * there are found to be insufficient resources available, causes the NN to

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

@@ -1137,8 +1137,7 @@ class NameNodeRpcServer implements NamenodeProtocols {
       return; // Return previous response
     }
 
-    metrics.incrCreateSymlinkOps();
-    /* We enforce the MAX_PATH_LENGTH limit even though a symlink target 
+    /* We enforce the MAX_PATH_LENGTH limit even though a symlink target
      * URI may refer to a non-HDFS file system. 
      */
     if (!checkPathLength(link)) {
@@ -1146,9 +1145,7 @@ class NameNodeRpcServer implements NamenodeProtocols {
                             " character limit");
                             
     }
-    if ("".equals(target)) {
-      throw new IOException("Invalid symlink target");
-    }
+
     final UserGroupInformation ugi = getRemoteUser();
 
     boolean success = false;