HDFS-15430. create should work when parent dir is internalDir and fallback configured. Contributed by Uma Maheswara Rao G.

(cherry picked from commit 1f2a80b5e5)

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

@@ -41,6 +41,7 @@
 import java.util.Objects;
 import java.util.Set;
 
+import com.google.common.base.Preconditions;
 import org.apache.hadoop.classification.InterfaceAudience;
 import org.apache.hadoop.classification.InterfaceStability;
 import org.apache.hadoop.conf.Configuration;
@@ -1180,7 +1181,41 @@ public FSDataOutputStream append(final Path f, final int bufferSize,
     public FSDataOutputStream create(final Path f,
         final FsPermission permission, final boolean overwrite,
         final int bufferSize, final short replication, final long blockSize,
-        final Progressable progress) throws AccessControlException {
+        final Progressable progress) throws IOException {
+      Preconditions.checkNotNull(f, "File cannot be null.");
+      if (InodeTree.SlashPath.equals(f)) {
+        throw new FileAlreadyExistsException(
+            "/ is not a file. The directory / already exist at: "
+                + theInternalDir.fullPath);
+      }
+
+      if (this.fsState.getRootFallbackLink() != null) {
+
+        if (theInternalDir.getChildren().containsKey(f.getName())) {
+          throw new FileAlreadyExistsException(
+              "A mount path(file/dir) already exist with the requested path: "
+                  + theInternalDir.getChildren().get(f.getName()).fullPath);
+        }
+
+        FileSystem linkedFallbackFs =
+            this.fsState.getRootFallbackLink().getTargetFileSystem();
+        Path parent = Path.getPathWithoutSchemeAndAuthority(
+            new Path(theInternalDir.fullPath));
+        String leaf = f.getName();
+        Path fileToCreate = new Path(parent, leaf);
+
+        try {
+          return linkedFallbackFs
+              .create(fileToCreate, permission, overwrite, bufferSize,
+                  replication, blockSize, progress);
+        } catch (IOException e) {
+          StringBuilder msg =
+              new StringBuilder("Failed to create file:").append(fileToCreate)
+                  .append(" at fallback : ").append(linkedFallbackFs.getUri());
+          LOG.error(msg.toString(), e);
+          throw e;
+        }
+      }
       throw readOnlyMountTable("create", f);
     }
 

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

@@ -33,6 +33,8 @@
 import java.util.Map.Entry;
 
 import java.util.Set;
+
+import com.google.common.base.Preconditions;
 import org.apache.hadoop.classification.InterfaceAudience;
 import org.apache.hadoop.classification.InterfaceStability;
 import org.apache.hadoop.conf.Configuration;
@@ -919,6 +921,41 @@ public FSDataOutputStream createInternal(final Path f,
         FileAlreadyExistsException, FileNotFoundException,
         ParentNotDirectoryException, UnsupportedFileSystemException,
         UnresolvedLinkException, IOException {
+      Preconditions.checkNotNull(f, "File cannot be null.");
+      if (InodeTree.SlashPath.equals(f)) {
+        throw new FileAlreadyExistsException(
+            "/ is not a file. The directory / already exist at: "
+                + theInternalDir.fullPath);
+      }
+
+      if (this.fsState.getRootFallbackLink() != null) {
+        if (theInternalDir.getChildren().containsKey(f.getName())) {
+          throw new FileAlreadyExistsException(
+              "A mount path(file/dir) already exist with the requested path: "
+                  + theInternalDir.getChildren().get(f.getName()).fullPath);
+        }
+
+        AbstractFileSystem linkedFallbackFs =
+            this.fsState.getRootFallbackLink().getTargetFileSystem();
+        Path parent = Path.getPathWithoutSchemeAndAuthority(
+            new Path(theInternalDir.fullPath));
+        String leaf = f.getName();
+        Path fileToCreate = new Path(parent, leaf);
+
+        try {
+          return linkedFallbackFs
+              .createInternal(fileToCreate, flag, absolutePermission,
+                  bufferSize, replication, blockSize, progress, checksumOpt,
+                  true);
+        } catch (IOException e) {
+          StringBuilder msg =
+              new StringBuilder("Failed to create file:").append(fileToCreate)
+                  .append(" at fallback : ").append(linkedFallbackFs.getUri());
+          LOG.error(msg.toString(), e);
+          throw e;
+        }
+      }
+
       throw readOnlyMountTable("create", f);
     }
 

hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/fs/viewfs/TestViewFileSystemLinkFallback.java

@@ -33,6 +33,7 @@
 
 import org.apache.hadoop.conf.Configuration;
 import org.apache.hadoop.fs.FSDataOutputStream;
+import org.apache.hadoop.fs.FileAlreadyExistsException;
 import org.apache.hadoop.fs.FileStatus;
 import org.apache.hadoop.fs.FileSystem;
 import org.apache.hadoop.fs.FileSystemTestHelper;
@@ -765,4 +766,151 @@ public void testMkdirsShouldReturnFalseWhenFallbackFSNotAvailable()
       assertTrue(fsTarget.exists(test));
     }
   }
+
+  /**
+   * Tests that the create file should be successful when the parent directory
+   * is same as the existent fallback directory. The new file should be created
+   * in fallback.
+   */
+  @Test
+  public void testCreateFileOnInternalMountDirWithSameDirTreeExistInFallback()
+      throws Exception {
+    Configuration conf = new Configuration();
+    ConfigUtil.addLink(conf, "/user1/hive/warehouse/partition-0",
+        new Path(targetTestRoot.toString()).toUri());
+    Path fallbackTarget = new Path(targetTestRoot, "fallbackDir");
+    Path dir1 = new Path(fallbackTarget, "user1/hive/warehouse/partition-0");
+    fsTarget.mkdirs(dir1);
+    ConfigUtil.addLinkFallback(conf, fallbackTarget.toUri());
+
+    try (FileSystem vfs = FileSystem.get(viewFsDefaultClusterUri, conf)) {
+      Path vfsTestFile = new Path("/user1/hive/warehouse/test.file");
+      Path testFileInFallback = Path.mergePaths(fallbackTarget, vfsTestFile);
+      assertFalse(fsTarget.exists(testFileInFallback));
+      assertTrue(fsTarget.exists(testFileInFallback.getParent()));
+      vfs.create(vfsTestFile).close();
+      assertTrue(fsTarget.exists(testFileInFallback));
+    }
+  }
+
+  /**
+   * Tests the making of a new directory which is not matching to any of
+   * internal directory.
+   */
+  @Test
+  public void testCreateNewFileWithOutMatchingToMountDirOrFallbackDirPath()
+      throws Exception {
+    Configuration conf = new Configuration();
+    ConfigUtil.addLink(conf, "/user1/hive/warehouse/partition-0",
+        new Path(targetTestRoot.toString()).toUri());
+    Path fallbackTarget = new Path(targetTestRoot, "fallbackDir");
+    fsTarget.mkdirs(fallbackTarget);
+    ConfigUtil.addLinkFallback(conf, fallbackTarget.toUri());
+    try (FileSystem vfs = FileSystem.get(viewFsDefaultClusterUri, conf)) {
+      Path vfsTestFile = new Path("/user2/test.file");
+      Path testFileInFallback = Path.mergePaths(fallbackTarget, vfsTestFile);
+      assertFalse(fsTarget.exists(testFileInFallback));
+      // user2 does not exist in fallback
+      assertFalse(fsTarget.exists(testFileInFallback.getParent()));
+      vfs.create(vfsTestFile).close();
+      // /user2/test.file should be created in fallback
+      assertTrue(fsTarget.exists(testFileInFallback));
+    }
+  }
+
+  /**
+   * Tests the making of a new file on root which is not matching to any of
+   * fallback files on root.
+   */
+  @Test
+  public void testCreateFileOnRootWithFallbackEnabled() throws Exception {
+    Configuration conf = new Configuration();
+    Path fallbackTarget = new Path(targetTestRoot, "fallbackDir");
+    fsTarget.mkdirs(fallbackTarget);
+
+    ConfigUtil.addLink(conf, "/user1/hive/",
+        new Path(targetTestRoot.toString()).toUri());
+    ConfigUtil.addLinkFallback(conf, fallbackTarget.toUri());
+
+    try (FileSystem vfs = FileSystem.get(viewFsDefaultClusterUri, conf)) {
+      Path vfsTestFile = new Path("/test.file");
+      Path testFileInFallback = Path.mergePaths(fallbackTarget, vfsTestFile);
+      assertFalse(fsTarget.exists(testFileInFallback));
+      vfs.create(vfsTestFile).close();
+      // /test.file should be created in fallback
+      assertTrue(fsTarget.exists(testFileInFallback));
+    }
+  }
+
+  /**
+   * Tests the create of a file on root where the path is matching to an
+   * existing file on fallback's file on root.
+   */
+  @Test (expected = FileAlreadyExistsException.class)
+  public void testCreateFileOnRootWithFallbackWithFileAlreadyExist()
+      throws Exception {
+    Configuration conf = new Configuration();
+    Path fallbackTarget = new Path(targetTestRoot, "fallbackDir");
+    Path testFile = new Path(fallbackTarget, "test.file");
+    // pre-creating test file in fallback.
+    fsTarget.create(testFile).close();
+
+    ConfigUtil.addLink(conf, "/user1/hive/",
+        new Path(targetTestRoot.toString()).toUri());
+    ConfigUtil.addLinkFallback(conf, fallbackTarget.toUri());
+
+    try (FileSystem vfs = FileSystem.get(viewFsDefaultClusterUri, conf)) {
+      Path vfsTestFile = new Path("/test.file");
+      assertTrue(fsTarget.exists(testFile));
+      vfs.create(vfsTestFile, false).close();
+    }
+  }
+
+  /**
+   * Tests the creating of a file where the path is same as mount link path.
+   */
+  @Test(expected= FileAlreadyExistsException.class)
+  public void testCreateFileWhereThePathIsSameAsItsMountLinkPath()
+      throws Exception {
+    Configuration conf = new Configuration();
+    Path fallbackTarget = new Path(targetTestRoot, "fallbackDir");
+    fsTarget.mkdirs(fallbackTarget);
+
+    ConfigUtil.addLink(conf, "/user1/hive/",
+        new Path(targetTestRoot.toString()).toUri());
+    ConfigUtil.addLinkFallback(conf, fallbackTarget.toUri());
+
+    try (FileSystem vfs = FileSystem.get(viewFsDefaultClusterUri, conf)) {
+      Path vfsTestDir = new Path("/user1/hive");
+      assertFalse(fsTarget.exists(Path.mergePaths(fallbackTarget, vfsTestDir)));
+      vfs.create(vfsTestDir).close();
+    }
+  }
+
+  /**
+   * Tests the create of a file where the path is same as one of of the internal
+   * dir path should fail.
+   */
+  @Test
+  public void testCreateFileSameAsInternalDirPath() throws Exception {
+    Configuration conf = new Configuration();
+    Path fallbackTarget = new Path(targetTestRoot, "fallbackDir");
+    fsTarget.mkdirs(fallbackTarget);
+    ConfigUtil.addLink(conf, "/user1/hive/",
+        new Path(targetTestRoot.toString()).toUri());
+    ConfigUtil.addLinkFallback(conf, fallbackTarget.toUri());
+
+    try (FileSystem vfs = FileSystem.get(viewFsDefaultClusterUri, conf)) {
+      Path vfsTestDir = new Path("/user1");
+      assertFalse(fsTarget.exists(Path.mergePaths(fallbackTarget, vfsTestDir)));
+      try {
+        vfs.create(vfsTestDir);
+        Assert.fail("Should fail to create file as this is an internal dir.");
+      } catch (NotInMountpointException e){
+        // This tree is part of internal tree. The above exception will be
+        // thrown from getDefaultReplication, getDefaultBlockSize APIs which was
+        // called in create API.
+      }
+    }
+  }
 }

hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/fs/viewfs/TestViewFileSystemOverloadSchemeWithHdfsScheme.java

@@ -39,7 +39,6 @@
 import org.apache.hadoop.hdfs.DFSConfigKeys;
 import org.apache.hadoop.hdfs.DistributedFileSystem;
 import org.apache.hadoop.hdfs.MiniDFSCluster;
-import org.apache.hadoop.security.AccessControlException;
 import org.apache.hadoop.test.PathUtils;
 import org.junit.After;
 import org.junit.Assert;
@@ -346,33 +345,6 @@ public void testCreateOnRootShouldFailWhenMountLinkConfigured()
     }
   }
 
-  /**
-   * Create mount links as follows
-   * hdfs://localhost:xxx/HDFSUser --> hdfs://localhost:xxx/HDFSUser/
-   * hdfs://localhost:xxx/local --> file://TEST_ROOT_DIR/root/
-   * fallback --> hdfs://localhost:xxx/HDFSUser/
-   *
-   * It will find fallback link, but root is not accessible and read only.
-   */
-  @Test(expected = AccessControlException.class, timeout = 30000)
-  public void testCreateOnRootShouldFailEvenFallBackMountLinkConfigured()
-      throws Exception {
-    final Path hdfsTargetPath = new Path(defaultFSURI + HDFS_USER_FOLDER);
-    addMountLinks(defaultFSURI.getAuthority(),
-        new String[] {HDFS_USER_FOLDER, LOCAL_FOLDER,
-            Constants.CONFIG_VIEWFS_LINK_FALLBACK },
-        new String[] {hdfsTargetPath.toUri().toString(),
-            localTargetDir.toURI().toString(),
-            hdfsTargetPath.toUri().toString() },
-        conf);
-    try (FileSystem fs = FileSystem.get(conf)) {
-      fs.createNewFile(new Path("/onRootWhenFallBack"));
-      Assert.fail(
-          "It should fail as root is read only in viewFS, even when configured"
-              + " with fallback.");
-    }
-  }
-
   /**
    * Create mount links as follows
    * hdfs://localhost:xxx/HDFSUser --> hdfs://localhost:xxx/HDFSUser/

hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/fs/viewfs/TestViewFsLinkFallback.java

@@ -17,6 +17,7 @@
  */
 package org.apache.hadoop.fs.viewfs;
 
+import static org.apache.hadoop.fs.CreateFlag.CREATE;
 import static org.junit.Assert.assertFalse;
 import static org.junit.Assert.assertNotNull;
 import static org.junit.Assert.assertTrue;
@@ -24,12 +25,15 @@
 import java.io.IOException;
 import java.net.URI;
 import java.net.URISyntaxException;
+import java.util.EnumSet;
 
 import org.apache.hadoop.conf.Configuration;
 import org.apache.hadoop.fs.AbstractFileSystem;
+import org.apache.hadoop.fs.FileAlreadyExistsException;
 import org.apache.hadoop.fs.FileStatus;
 import org.apache.hadoop.fs.FileSystem;
 import org.apache.hadoop.fs.FsConstants;
+import org.apache.hadoop.fs.Options;
 import org.apache.hadoop.fs.Path;
 import org.apache.hadoop.fs.permission.FsPermission;
 import org.apache.hadoop.hdfs.DFSConfigKeys;
@@ -294,4 +298,154 @@ public void testMkdirShouldFailWhenFallbackFSNotAvailable()
     assertTrue(fsTarget.exists(test));
   }
 
+  /**
+   * Tests that the create file should be successful when the parent directory
+   * is same as the existent fallback directory. The new file should be created
+   * in fallback.
+   */
+  @Test
+  public void testCreateFileOnInternalMountDirWithSameDirTreeExistInFallback()
+      throws Exception {
+    Configuration conf = new Configuration();
+    ConfigUtil.addLink(conf, "/user1/hive/warehouse/partition-0",
+        new Path(targetTestRoot.toString()).toUri());
+    Path fallbackTarget = new Path(targetTestRoot, "fallbackDir");
+    Path dir1 = new Path(fallbackTarget, "user1/hive/warehouse/partition-0");
+    fsTarget.mkdirs(dir1);
+    ConfigUtil.addLinkFallback(conf, fallbackTarget.toUri());
+
+    AbstractFileSystem vfs =
+        AbstractFileSystem.get(viewFsDefaultClusterUri, conf);
+    Path vfsTestFile = new Path("/user1/hive/warehouse/test.file");
+    Path testFileInFallback = Path.mergePaths(fallbackTarget, vfsTestFile);
+    assertFalse(fsTarget.exists(testFileInFallback));
+    assertTrue(fsTarget.exists(testFileInFallback.getParent()));
+    vfs.create(vfsTestFile, EnumSet.of(CREATE),
+        Options.CreateOpts.perms(FsPermission.getDefault())).close();
+    assertTrue(fsTarget.exists(testFileInFallback));
+
+  }
+
+  /**
+   * Tests the making of a new directory which is not matching to any of
+   * internal directory.
+   */
+  @Test
+  public void testCreateNewFileWithOutMatchingToMountDirOrFallbackDirPath()
+      throws Exception {
+    Configuration conf = new Configuration();
+    ConfigUtil.addLink(conf, "/user1/hive/warehouse/partition-0",
+        new Path(targetTestRoot.toString()).toUri());
+    Path fallbackTarget = new Path(targetTestRoot, "fallbackDir");
+    fsTarget.mkdirs(fallbackTarget);
+    ConfigUtil.addLinkFallback(conf, fallbackTarget.toUri());
+    AbstractFileSystem vfs =
+        AbstractFileSystem.get(viewFsDefaultClusterUri, conf);
+    Path vfsTestFile = new Path("/user2/test.file");
+    Path testFileInFallback = Path.mergePaths(fallbackTarget, vfsTestFile);
+    assertFalse(fsTarget.exists(testFileInFallback));
+    // user2 does not exist in fallback
+    assertFalse(fsTarget.exists(testFileInFallback.getParent()));
+    vfs.create(vfsTestFile, EnumSet.of(CREATE),
+        Options.CreateOpts.perms(FsPermission.getDefault()),
+        Options.CreateOpts.createParent()).close();
+    // /user2/test.file should be created in fallback
+    assertTrue(fsTarget.exists(testFileInFallback));
+  }
+
+  /**
+   * Tests the making of a new file on root which is not matching to any of
+   * fallback files on root.
+   */
+  @Test
+  public void testCreateFileOnRootWithFallbackEnabled()
+      throws Exception {
+    Configuration conf = new Configuration();
+    Path fallbackTarget = new Path(targetTestRoot, "fallbackDir");
+    fsTarget.mkdirs(fallbackTarget);
+
+    ConfigUtil.addLink(conf, "/user1/hive/",
+        new Path(targetTestRoot.toString()).toUri());
+    ConfigUtil.addLinkFallback(conf, fallbackTarget.toUri());
+
+    AbstractFileSystem vfs =
+        AbstractFileSystem.get(viewFsDefaultClusterUri, conf);
+    Path vfsTestFile = new Path("/test.file");
+    Path testFileInFallback = Path.mergePaths(fallbackTarget, vfsTestFile);
+    assertFalse(fsTarget.exists(testFileInFallback));
+    vfs.create(vfsTestFile, EnumSet.of(CREATE),
+        Options.CreateOpts.perms(FsPermission.getDefault())).close();
+    // /test.file should be created in fallback
+    assertTrue(fsTarget.exists(testFileInFallback));
+
+  }
+
+  /**
+   * Tests the create of a file on root where the path is matching to an
+   * existing file on fallback's file on root.
+   */
+  @Test (expected = FileAlreadyExistsException.class)
+  public void testCreateFileOnRootWithFallbackWithFileAlreadyExist()
+      throws Exception {
+    Configuration conf = new Configuration();
+    Path fallbackTarget = new Path(targetTestRoot, "fallbackDir");
+    Path testFile = new Path(fallbackTarget, "test.file");
+    // pre-creating test file in fallback.
+    fsTarget.create(testFile).close();
+
+    ConfigUtil.addLink(conf, "/user1/hive/",
+        new Path(targetTestRoot.toString()).toUri());
+    ConfigUtil.addLinkFallback(conf, fallbackTarget.toUri());
+
+    AbstractFileSystem vfs =
+        AbstractFileSystem.get(viewFsDefaultClusterUri, conf);
+    Path vfsTestFile = new Path("/test.file");
+    assertTrue(fsTarget.exists(testFile));
+    vfs.create(vfsTestFile, EnumSet.of(CREATE),
+        Options.CreateOpts.perms(FsPermission.getDefault())).close();
+  }
+
+  /**
+   * Tests the creating of a file where the path is same as mount link path.
+   */
+  @Test(expected= FileAlreadyExistsException.class)
+  public void testCreateFileWhereThePathIsSameAsItsMountLinkPath()
+      throws Exception {
+    Configuration conf = new Configuration();
+    Path fallbackTarget = new Path(targetTestRoot, "fallbackDir");
+    fsTarget.mkdirs(fallbackTarget);
+
+    ConfigUtil.addLink(conf, "/user1/hive/",
+        new Path(targetTestRoot.toString()).toUri());
+    ConfigUtil.addLinkFallback(conf, fallbackTarget.toUri());
+
+    AbstractFileSystem vfs =
+        AbstractFileSystem.get(viewFsDefaultClusterUri, conf);
+    Path vfsTestDir = new Path("/user1/hive");
+    assertFalse(fsTarget.exists(Path.mergePaths(fallbackTarget, vfsTestDir)));
+    vfs.create(vfsTestDir, EnumSet.of(CREATE),
+        Options.CreateOpts.perms(FsPermission.getDefault())).close();
+  }
+
+  /**
+   * Tests the create of a file where the path is same as one of of the internal
+   * dir path should fail.
+   */
+  @Test(expected = FileAlreadyExistsException.class)
+  public void testCreateFileSameAsInternalDirPath()
+      throws Exception {
+    Configuration conf = new Configuration();
+    Path fallbackTarget = new Path(targetTestRoot, "fallbackDir");
+    fsTarget.mkdirs(fallbackTarget);
+    ConfigUtil.addLink(conf, "/user1/hive/",
+        new Path(targetTestRoot.toString()).toUri());
+    ConfigUtil.addLinkFallback(conf, fallbackTarget.toUri());
+
+    AbstractFileSystem vfs =
+        AbstractFileSystem.get(viewFsDefaultClusterUri, conf);
+    Path vfsTestDir = new Path("/user1");
+    assertFalse(fsTarget.exists(Path.mergePaths(fallbackTarget, vfsTestDir)));
+    vfs.create(vfsTestDir, EnumSet.of(CREATE),
+        Options.CreateOpts.perms(FsPermission.getDefault())).close();
+  }
 }