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

public static FSDataInputStream getPreviousJobHistoryFileStream(
    Configuration conf, ApplicationAttemptId applicationAttemptId)
    throws IOException {
  FSDataInputStream in = null;
  Path historyFile = null;
  String jobId =
      TypeConverter.fromYarn(applicationAttemptId.getApplicationId())
        .toString();
  String jobhistoryDir =
      JobHistoryUtils.getConfiguredHistoryStagingDirPrefix(conf, jobId);
  Path histDirPath =
      FileContext.getFileContext(conf).makeQualified(new Path(jobhistoryDir));
  FileContext fc = FileContext.getFileContext(histDirPath.toUri(), conf);
  // read the previous history file
  historyFile =
      fc.makeQualified(JobHistoryUtils.getStagingJobHistoryFile(histDirPath,
        jobId, (applicationAttemptId.getAttemptId() - 1)));
  LOG.info("History file is at " + historyFile);
  in = fc.open(historyFile);
  return in;
}
 

public static FSDataInputStream getPreviousJobHistoryFileStream(
    Configuration conf, ApplicationAttemptId applicationAttemptId)
    throws IOException {
  FSDataInputStream in = null;
  Path historyFile = null;
  String jobId =
      TypeConverter.fromYarn(applicationAttemptId.getApplicationId())
        .toString();
  String jobhistoryDir =
      JobHistoryUtils.getConfiguredHistoryStagingDirPrefix(conf, jobId);
  Path histDirPath =
      FileContext.getFileContext(conf).makeQualified(new Path(jobhistoryDir));
  FileContext fc = FileContext.getFileContext(histDirPath.toUri(), conf);
  // read the previous history file
  historyFile =
      fc.makeQualified(JobHistoryUtils.getStagingJobHistoryFile(histDirPath,
        jobId, (applicationAttemptId.getAttemptId() - 1)));
  LOG.info("History file is at " + historyFile);
  in = fc.open(historyFile);
  return in;
}
 

private void testCopyPartialHelper(int dataSize, int offset, long size) throws IOException
  {
    FileUtils.deleteQuietly(new File("target/IOUtilsTest"));
    File file = new File("target/IOUtilsTest/testCopyPartial/input");
    createDataFile(file, dataSize);

    FileContext fileContext = FileContext.getFileContext();
    DataInputStream inputStream = fileContext.open(new Path(file.getAbsolutePath()));

    Path output = new Path("target/IOUtilsTest/testCopyPartial/output");
    DataOutputStream outputStream = fileContext.create(output, EnumSet
        .of(CreateFlag.CREATE, CreateFlag.OVERWRITE), Options.CreateOpts.CreateParent.createParent());

    if (offset == 0) {
      IOUtils.copyPartial(inputStream, size, outputStream);
    } else {
      IOUtils.copyPartial(inputStream, offset, size, outputStream);
    }

    outputStream.close();

    Assert.assertTrue("output exists", fileContext.util().exists(output));
    Assert.assertEquals("output size", size, fileContext.getFileStatus(output).getLen());
//    FileUtils.deleteQuietly(new File("target/IOUtilsTest"));
  }
 

public LogReader(Configuration conf, Path remoteAppLogFile)
    throws IOException {
  FileContext fileContext =
      FileContext.getFileContext(remoteAppLogFile.toUri(), conf);
  this.fsDataIStream = fileContext.open(remoteAppLogFile);
  reader =
      new TFile.Reader(this.fsDataIStream, fileContext.getFileStatus(
          remoteAppLogFile).getLen(), conf);
  this.scanner = reader.createScanner();
}
 

private String getJobSummary(FileContext fc, Path path) throws IOException {
  Path qPath = fc.makeQualified(path);
  FSDataInputStream in = fc.open(qPath);
  String jobSummaryString = in.readUTF();
  in.close();
  return jobSummaryString;
}
 

private static String getJobSummary(FileContext fc, Path path)
    throws IOException {
  Path qPath = fc.makeQualified(path);
  FSDataInputStream in = fc.open(qPath);
  String jobSummaryString = in.readUTF();
  in.close();
  return jobSummaryString;
}
 

public LogReader(Configuration conf, Path remoteAppLogFile)
    throws IOException {
  FileContext fileContext = FileContext.getFileContext(conf);
  this.fsDataIStream = fileContext.open(remoteAppLogFile);
  reader =
      new TFile.Reader(this.fsDataIStream, fileContext.getFileStatus(
          remoteAppLogFile).getLen(), conf);
  this.scanner = reader.createScanner();
}
 

private String getJobSummary(FileContext fc, Path path) throws IOException {
  Path qPath = fc.makeQualified(path);
  FSDataInputStream in = fc.open(qPath);
  String jobSummaryString = in.readUTF();
  in.close();
  return jobSummaryString;
}
 

private static String getJobSummary(FileContext fc, Path path)
    throws IOException {
  Path qPath = fc.makeQualified(path);
  FSDataInputStream in = fc.open(qPath);
  String jobSummaryString = in.readUTF();
  in.close();
  return jobSummaryString;
}
 

@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);
  }
}
 

@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);
  }
}