import org.apache.hadoop.hdfs.server.namenode.FSEditLogLoader.EditLogValidation; //导入依赖的package包/类
static FSEditLogLoader.EditLogValidation validateEditLog(File file)
    throws IOException {
  EditLogFileInputStream in;
  try {
    in = new EditLogFileInputStream(file);
    in.getVersion(true); // causes us to read the header
  } catch (LogHeaderCorruptException e) {
    // If the header is malformed or the wrong value, this indicates a corruption
    LOG.warn("Log file " + file + " has no valid header", e);
    return new FSEditLogLoader.EditLogValidation(0,
        HdfsConstants.INVALID_TXID, true);
  }
  
  try {
    return FSEditLogLoader.validateEditLog(in);
  } finally {
    IOUtils.closeStream(in);
  }
}
 

import org.apache.hadoop.hdfs.server.namenode.FSEditLogLoader.EditLogValidation; //导入依赖的package包/类
/**
 * @param file          File being scanned and validated.
 * @param maxTxIdToScan Maximum Tx ID to try to scan.
 *                      The scan returns after reading this or a higher
 *                      ID. The file portion beyond this ID is
 *                      potentially being updated.
 * @return Result of the validation
 * @throws IOException
 */
static FSEditLogLoader.EditLogValidation scanEditLog(File file,
    long maxTxIdToScan, boolean verifyVersion)
    throws IOException {
  EditLogFileInputStream in;
  try {
    in = new EditLogFileInputStream(file);
    // read the header, initialize the inputstream, but do not check the
    // layoutversion
    in.getVersion(verifyVersion);
  } catch (LogHeaderCorruptException e) {
    LOG.warn("Log file " + file + " has no valid header", e);
    return new FSEditLogLoader.EditLogValidation(0,
        HdfsServerConstants.INVALID_TXID, true);
  }

  try {
    return FSEditLogLoader.scanEditLog(in, maxTxIdToScan);
  } finally {
    IOUtils.closeStream(in);
  }
}
 

import org.apache.hadoop.hdfs.server.namenode.FSEditLogLoader.EditLogValidation; //导入依赖的package包/类
@Test
public void testValidateEditLogWithCorruptHeader() throws IOException {
  File testDir = new File(TEST_DIR, "testValidateEditLogWithCorruptHeader");
  SortedMap<Long, Long> offsetToTxId = Maps.newTreeMap();
  File logFile = prepareUnfinalizedTestEditLog(testDir, 2, offsetToTxId);
  RandomAccessFile rwf = new RandomAccessFile(logFile, "rw");
  try {
    rwf.seek(0);
    rwf.writeLong(42); // corrupt header
  } finally {
    rwf.close();
  }
  EditLogValidation validation =
      EditLogFileInputStream.scanEditLog(logFile, Long.MAX_VALUE, true);
  assertTrue(validation.hasCorruptHeader());
}
 

import org.apache.hadoop.hdfs.server.namenode.FSEditLogLoader.EditLogValidation; //导入依赖的package包/类
@Test
public void testValidateEditLogWithCorruptHeader() throws IOException {
  File testDir = new File(TEST_DIR, "testValidateEditLogWithCorruptHeader");
  SortedMap<Long, Long> offsetToTxId = Maps.newTreeMap();
  File logFile = prepareUnfinalizedTestEditLog(testDir, 2, offsetToTxId);
  RandomAccessFile rwf = new RandomAccessFile(logFile, "rw");
  try {
    rwf.seek(0);
    rwf.writeLong(42); // corrupt header
  } finally {
    rwf.close();
  }
  EditLogValidation validation = EditLogFileInputStream.validateEditLog(logFile);
  assertTrue(validation.hasCorruptHeader());
}
 

import org.apache.hadoop.hdfs.server.namenode.FSEditLogLoader.EditLogValidation; //导入依赖的package包/类
@Test
public void testValidateEmptyEditLog() throws IOException {
  File testDir = new File(TEST_DIR, "testValidateEmptyEditLog");
  SortedMap<Long, Long> offsetToTxId = Maps.newTreeMap();
  File logFile = prepareUnfinalizedTestEditLog(testDir, 0, offsetToTxId);
  // Truncate the file so that there is nothing except the header and
  // layout flags section.
  truncateFile(logFile, 8);
  EditLogValidation validation =
      EditLogFileInputStream.validateEditLog(logFile);
  assertTrue(!validation.hasCorruptHeader());
  assertEquals(HdfsConstants.INVALID_TXID, validation.getEndTxId());
}
 

import org.apache.hadoop.hdfs.server.namenode.FSEditLogLoader.EditLogValidation; //导入依赖的package包/类
@Test
public void testValidateEmptyEditLog() throws IOException {
  File testDir = new File(TEST_DIR, "testValidateEmptyEditLog");
  SortedMap<Long, Long> offsetToTxId = Maps.newTreeMap();
  File logFile = prepareUnfinalizedTestEditLog(testDir, 0, offsetToTxId);
  // Truncate the file so that there is nothing except the header and
  // layout flags section.
  truncateFile(logFile, 8);
  EditLogValidation validation =
      EditLogFileInputStream.scanEditLog(logFile, Long.MAX_VALUE, true);
  assertTrue(!validation.hasCorruptHeader());
  assertEquals(HdfsServerConstants.INVALID_TXID, validation.getEndTxId());
}
 

import org.apache.hadoop.hdfs.server.namenode.FSEditLogLoader.EditLogValidation; //导入依赖的package包/类
@Test
public void testPreallocation() throws IOException {
  Configuration conf = new Configuration();
  MiniDFSCluster cluster = new MiniDFSCluster(conf, 0, true, null);

  StorageDirectory sd = cluster.getNameNode().getFSImage()
    .storage.getStorageDir(0);
  File editLog = NNStorage.getInProgressEditsFile(sd, 0);

  EditLogValidation validation = EditLogFileInputStream.validateEditLog(editLog);
  assertEquals("Edit log should contain a header as valid length",
      HEADER_LEN, validation.getValidLength());
  assertEquals(1, validation.getNumTransactions());
  assertEquals("Edit log should have 1MB pre-allocated",
      PREALLOCATION_LENGTH, editLog.length());
  

  cluster.getFileSystem().mkdirs(new Path("/tmp"),
      new FsPermission((short)777));

  long oldLength = validation.getValidLength();
  validation = EditLogFileInputStream.validateEditLog(editLog);
  assertTrue("Edit log should have more valid data after writing a txn " +
      "(was: " + oldLength + " now: " + validation.getValidLength() + ")",
      validation.getValidLength() > oldLength);
  assertEquals(2, validation.getNumTransactions());

  assertEquals("Edit log should be 1MB long, plus 4 bytes for the version number",
      PREALLOCATION_LENGTH, editLog.length());
}
 

import org.apache.hadoop.hdfs.server.namenode.FSEditLogLoader.EditLogValidation; //导入依赖的package包/类
@Test
public void testValidateEmptyEditLog() throws IOException {
  File testDir = new File(TEST_DIR, "testValidateEmptyEditLog");
  SortedMap<Long, Long> offsetToTxId = Maps.newTreeMap();
  File logFile = prepareUnfinalizedTestEditLog(testDir, 0, offsetToTxId);
  // Truncate the file so that there is nothing except the header
  truncateFile(logFile, 4);
  EditLogValidation validation =
      EditLogFileInputStream.validateEditLog(logFile);
  assertTrue(!validation.hasCorruptHeader());
  assertEquals(HdfsConstants.INVALID_TXID, validation.getEndTxId());
}
 

import org.apache.hadoop.hdfs.server.namenode.FSEditLogLoader.EditLogValidation; //导入依赖的package包/类
/** 
 * Count the number of valid transactions in a log.
 * This will update the lastTxId of the EditLogFile or
 * mark it as corrupt if it is.
 */
public void validateLog() throws IOException {
  EditLogValidation val = EditLogFileInputStream.validateEditLog(file);
  if (val.getNumTransactions() == 0) {
    markCorrupt();
  } else {
    this.lastTxId = val.getEndTxId();
  }
}
 

import org.apache.hadoop.hdfs.server.namenode.FSEditLogLoader.EditLogValidation; //导入依赖的package包/类
static FSEditLogLoader.EditLogValidation scanEditLog(File file)
    throws IOException {
  EditLogFileInputStream in;
  try {
    in = new EditLogFileInputStream(file);
    // read the header, initialize the inputstream, but do not check the
    // layoutversion
    in.getVersion(false);
  } catch (LogHeaderCorruptException e) {
    LOG.warn("Log file " + file + " has no valid header", e);
    return new FSEditLogLoader.EditLogValidation(0,
        HdfsConstants.INVALID_TXID, true);
  }

  long lastPos = 0;
  long lastTxId = HdfsConstants.INVALID_TXID;
  long numValid = 0;
  try {
    while (true) {
      long txid = HdfsConstants.INVALID_TXID;
      lastPos = in.getPosition();
      try {
        if ((txid = in.scanNextOp()) == HdfsConstants.INVALID_TXID) {
          break;
        }
      } catch (Throwable t) {
        FSImage.LOG.warn("Caught exception after scanning through "
            + numValid + " ops from " + in
            + " while determining its valid length. Position was "
            + lastPos, t);
        in.resync();
        FSImage.LOG.warn("After resync, position is " + in.getPosition());
        continue;
      }
      if (lastTxId == HdfsConstants.INVALID_TXID || txid > lastTxId) {
        lastTxId = txid;
      }
      numValid++;
    }
    return new EditLogValidation(lastPos, lastTxId, false);
  } finally {
    IOUtils.closeStream(in);
  }
}
 

import org.apache.hadoop.hdfs.server.namenode.FSEditLogLoader.EditLogValidation; //导入依赖的package包/类
/** 
 * Find out where the edit log ends.
 * This will update the lastTxId of the EditLogFile or
 * mark it as corrupt if it is.
 */
public void validateLog() throws IOException {
  EditLogValidation val = EditLogFileInputStream.validateEditLog(file);
  this.lastTxId = val.getEndTxId();
  this.hasCorruptHeader = val.hasCorruptHeader();
}
 

import org.apache.hadoop.hdfs.server.namenode.FSEditLogLoader.EditLogValidation; //导入依赖的package包/类
public void scanLog() throws IOException {
  EditLogValidation val = EditLogFileInputStream.scanEditLog(file);
  this.lastTxId = val.getEndTxId();
  this.hasCorruptHeader = val.hasCorruptHeader();
}