org.apache.hadoop.fs.FileContext#rename ( )源码实例Demo

@Override
public void move(Directory fromDir, Directory toDir, String fileName, IOContext ioContext) throws IOException {
  
  Directory baseFromDir = getBaseDir(fromDir);
  Directory baseToDir = getBaseDir(toDir);
  
  if (baseFromDir instanceof HdfsDirectory && baseToDir instanceof HdfsDirectory) {
    Path dir1 = ((HdfsDirectory) baseFromDir).getHdfsDirPath();
    Path dir2 = ((HdfsDirectory) baseToDir).getHdfsDirPath();
    Path file1 = new Path(dir1, fileName);
    Path file2 = new Path(dir2, fileName);
    FileContext fileContext = FileContext.getFileContext(getConf(dir1));
    fileContext.rename(file1, file2);
    return;
  }

  super.move(fromDir, toDir, fileName, ioContext);
}
 

/**
 * Tests that an edits log created using CreateEditsLog is valid and can be
 * loaded successfully by a namenode.
 */
@Test(timeout=60000)
public void testCanLoadCreatedEditsLog() throws Exception {
  // Format namenode.
  HdfsConfiguration conf = new HdfsConfiguration();
  File nameDir = new File(HDFS_DIR, "name");
  conf.set(DFS_NAMENODE_NAME_DIR_KEY, Util.fileAsURI(nameDir).toString());
  DFSTestUtil.formatNameNode(conf);

  // Call CreateEditsLog and move the resulting edits to the name dir.
  CreateEditsLog.main(new String[] { "-f", "1000", "0", "1", "-d",
    TEST_DIR.getAbsolutePath() });
  Path editsWildcard = new Path(TEST_DIR.getAbsolutePath(), "*");
  FileContext localFc = FileContext.getLocalFSFileContext();
  for (FileStatus edits: localFc.util().globStatus(editsWildcard)) {
    Path src = edits.getPath();
    Path dst = new Path(new File(nameDir, "current").getAbsolutePath(),
      src.getName());
    localFc.rename(src, dst);
  }

  // Start a namenode to try to load the edits.
  cluster = new MiniDFSCluster.Builder(conf)
    .format(false)
    .manageNameDfsDirs(false)
    .waitSafeMode(false)
    .build();
  cluster.waitClusterUp();

  // Test successful, because no exception thrown.
}
 

/**
 * Tests that an edits log created using CreateEditsLog is valid and can be
 * loaded successfully by a namenode.
 */
@Test(timeout=60000)
public void testCanLoadCreatedEditsLog() throws Exception {
  // Format namenode.
  HdfsConfiguration conf = new HdfsConfiguration();
  File nameDir = new File(HDFS_DIR, "name");
  conf.set(DFS_NAMENODE_NAME_DIR_KEY, Util.fileAsURI(nameDir).toString());
  DFSTestUtil.formatNameNode(conf);

  // Call CreateEditsLog and move the resulting edits to the name dir.
  CreateEditsLog.main(new String[] { "-f", "1000", "0", "1", "-d",
    TEST_DIR.getAbsolutePath() });
  Path editsWildcard = new Path(TEST_DIR.getAbsolutePath(), "*");
  FileContext localFc = FileContext.getLocalFSFileContext();
  for (FileStatus edits: localFc.util().globStatus(editsWildcard)) {
    Path src = edits.getPath();
    Path dst = new Path(new File(nameDir, "current").getAbsolutePath(),
      src.getName());
    localFc.rename(src, dst);
  }

  // Start a namenode to try to load the edits.
  cluster = new MiniDFSCluster.Builder(conf)
    .format(false)
    .manageNameDfsDirs(false)
    .waitSafeMode(false)
    .build();
  cluster.waitClusterUp();

  // Test successful, because no exception thrown.
}
 

@Override
public void commit() throws IOException {
    checkIsNotTmp();
    // FileContext supports atomic rename, whereas FileSystem doesn't
    FileContext fc = FileContext.getFileContext(_hadoopConf);
    Path dest = new Path(_path.getParent(), BLOBSTORE_DATA_FILE);
    if (_mustBeNew) {
        fc.rename(_path, dest);
    } else {
        fc.rename(_path, dest, Options.Rename.OVERWRITE);
    }
    // Note, we could add support for setting the replication factor
}
 

@Override
public Object restore() throws IOException
{
  FileContext fc = FileContext.getFileContext(fs.getUri());

  // recover from wherever it was left
  if (fc.util().exists(snapshotBackupPath)) {
    LOG.warn("Incomplete checkpoint, reverting to {}", snapshotBackupPath);
    fc.rename(snapshotBackupPath, snapshotPath, Rename.OVERWRITE);

    // combine logs (w/o append, create new file)
    Path tmpLogPath = new Path(basedir, "log.combined");
    try (FSDataOutputStream fsOut = fc.create(tmpLogPath, EnumSet.of(CreateFlag.CREATE, CreateFlag.OVERWRITE))) {
      try (FSDataInputStream fsIn = fc.open(logBackupPath)) {
        IOUtils.copy(fsIn, fsOut);
      }

      try (FSDataInputStream fsIn = fc.open(logPath)) {
        IOUtils.copy(fsIn, fsOut);
      }
    }

    fc.rename(tmpLogPath, logPath, Rename.OVERWRITE);
    fc.delete(logBackupPath, false);
  } else {
    // we have log backup, but no checkpoint backup
    // failure between log rotation and writing checkpoint
    if (fc.util().exists(logBackupPath)) {
      LOG.warn("Found {}, did checkpointing fail?", logBackupPath);
      fc.rename(logBackupPath, logPath, Rename.OVERWRITE);
    }
  }

  if (!fc.util().exists(snapshotPath)) {
    LOG.debug("No existing checkpoint.");
    return null;
  }

  LOG.debug("Reading checkpoint {}", snapshotPath);
  InputStream is = fc.open(snapshotPath);
  // indeterministic class loading behavior
  // http://stackoverflow.com/questions/9110677/readresolve-not-working-an-instance-of-guavas-serializedform-appears
  final ClassLoader loader = Thread.currentThread().getContextClassLoader();
  try (ObjectInputStream ois = new ObjectInputStream(is)
  {
    @Override
    protected Class<?> resolveClass(ObjectStreamClass objectStreamClass)
        throws IOException, ClassNotFoundException
    {
      return Class.forName(objectStreamClass.getName(), true, loader);
    }
  }) {
    return ois.readObject();
  } catch (ClassNotFoundException cnfe) {
    throw new IOException("Failed to read checkpointed state", cnfe);
  }
}
 

public void renameWithOverwrite(Directory dir, String fileName, String toName) throws IOException {
  String hdfsDirPath = getPath(dir);
  FileContext fileContext = FileContext.getFileContext(getConf(new Path(hdfsDirPath)));
  fileContext.rename(new Path(hdfsDirPath, fileName), new Path(hdfsDirPath, toName), Options.Rename.OVERWRITE);
}
 

@Override
public Object restore() throws IOException
{
  FileContext fc = FileContext.getFileContext(fs.getUri());

  // recover from wherever it was left
  if (fc.util().exists(snapshotBackupPath)) {
    LOG.warn("Incomplete checkpoint, reverting to {}", snapshotBackupPath);
    fc.rename(snapshotBackupPath, snapshotPath, Rename.OVERWRITE);

    // combine logs (w/o append, create new file)
    Path tmpLogPath = new Path(basedir, "log.combined");
    try (FSDataOutputStream fsOut = fc.create(tmpLogPath, EnumSet.of(CreateFlag.CREATE, CreateFlag.OVERWRITE))) {
      try (FSDataInputStream fsIn = fc.open(logBackupPath)) {
        IOUtils.copy(fsIn, fsOut);
      }

      try (FSDataInputStream fsIn = fc.open(logPath)) {
        IOUtils.copy(fsIn, fsOut);
      }
    }

    fc.rename(tmpLogPath, logPath, Rename.OVERWRITE);
    fc.delete(logBackupPath, false);
  } else {
    // we have log backup, but no checkpoint backup
    // failure between log rotation and writing checkpoint
    if (fc.util().exists(logBackupPath)) {
      LOG.warn("Found {}, did checkpointing fail?", logBackupPath);
      fc.rename(logBackupPath, logPath, Rename.OVERWRITE);
    }
  }

  if (!fc.util().exists(snapshotPath)) {
    LOG.debug("No existing checkpoint.");
    return null;
  }

  LOG.debug("Reading checkpoint {}", snapshotPath);
  InputStream is = fc.open(snapshotPath);
  // indeterministic class loading behavior
  // http://stackoverflow.com/questions/9110677/readresolve-not-working-an-instance-of-guavas-serializedform-appears
  final ClassLoader loader = Thread.currentThread().getContextClassLoader();
  try (ObjectInputStream ois = new ObjectInputStream(is)
  {
    @Override
    protected Class<?> resolveClass(ObjectStreamClass objectStreamClass)
        throws IOException, ClassNotFoundException
    {
      return Class.forName(objectStreamClass.getName(), true, loader);
    }
  }) {
    return ois.readObject();
  } catch (ClassNotFoundException cnfe) {
    throw new IOException("Failed to read checkpointed state", cnfe);
  }
}
 

/**
 * A wrapper around {@link FileContext#rename(Path, Path, Options.Rename...)}}.
 */
public static void renamePath(FileContext fc, Path oldName, Path newName, boolean overwrite)
    throws IOException {
  Options.Rename renameOptions = (overwrite) ? Options.Rename.OVERWRITE : Options.Rename.NONE;
  fc.rename(oldName, newName, renameOptions);
}
 

public static void main(String[] args) throws IOException {
    FileContext fileContext = FileContext.getFileContext(new Configuration());

    Path src = new Path("/tmp/garmadon/test");
    Path dst = new Path("/tmp/garmadon/test2");

    fileContext.mkdir(src, FsPermission.getDefault(), true);

    fileContext.rename(src, dst, Options.Rename.OVERWRITE);

    fileContext.listStatus(dst);

    fileContext.delete(dst, false);
}