import org.apache.hadoop.hdfs.server.namenode.FSEditLogLoader; //导入依赖的package包/类
/**
 * Construct BookKeeper edit log input stream. 
 * Starts reading from firstBookKeeperEntry. This allows the stream
 * to take a shortcut during recovery, as it doesn't have to read
 * every edit log transaction to find out what the last one is.
 */
BookKeeperEditLogInputStream(LedgerHandle lh, EditLogLedgerMetadata metadata,
                             long firstBookKeeperEntry) 
    throws IOException {
  this.lh = lh;
  this.firstTxId = metadata.getFirstTxId();
  this.lastTxId = metadata.getLastTxId();
  this.logVersion = metadata.getDataLayoutVersion();
  this.inProgress = metadata.isInProgress();

  if (firstBookKeeperEntry < 0
      || firstBookKeeperEntry > lh.getLastAddConfirmed()) {
    throw new IOException("Invalid first bk entry to read: "
        + firstBookKeeperEntry + ", LAC: " + lh.getLastAddConfirmed());
  }
  BufferedInputStream bin = new BufferedInputStream(
      new LedgerInputStream(lh, firstBookKeeperEntry));
  tracker = new FSEditLogLoader.PositionTrackingInputStream(bin);
  DataInputStream in = new DataInputStream(tracker);

  reader = new FSEditLogOp.Reader(in, tracker, logVersion);
}
 

import org.apache.hadoop.hdfs.server.namenode.FSEditLogLoader; //导入依赖的package包/类
/**
 * Construct BookKeeper edit log input stream. 
 * Starts reading from firstBookKeeperEntry. This allows the stream
 * to take a shortcut during recovery, as it doesn't have to read
 * every edit log transaction to find out what the last one is.
 */
BookKeeperEditLogInputStream(LedgerHandle lh, EditLogLedgerMetadata metadata,
                             long firstBookKeeperEntry) 
    throws IOException {
  this.lh = lh;
  this.firstTxId = metadata.getFirstTxId();
  this.lastTxId = metadata.getLastTxId();
  this.logVersion = metadata.getDataLayoutVersion();
  this.inProgress = metadata.isInProgress();

  if (firstBookKeeperEntry < 0
      || firstBookKeeperEntry > lh.getLastAddConfirmed()) {
    throw new IOException("Invalid first bk entry to read: "
        + firstBookKeeperEntry + ", LAC: " + lh.getLastAddConfirmed());
  }
  BufferedInputStream bin = new BufferedInputStream(
      new LedgerInputStream(lh, firstBookKeeperEntry));
  tracker = new FSEditLogLoader.PositionTrackingInputStream(bin);
  DataInputStream in = new DataInputStream(tracker);

  reader = FSEditLogOp.Reader.create(in, tracker, logVersion);
}
 

import org.apache.hadoop.hdfs.server.namenode.FSEditLogLoader; //导入依赖的package包/类
public static FSEditLogLoader.EditLogValidation validateEditLog(
    LedgerHandleProvider ledgerProvider,
    EditLogLedgerMetadata ledgerMetadata) throws IOException {
  BookKeeperEditLogInputStream in;
  try {
    in = new BookKeeperEditLogInputStream(ledgerProvider,
        ledgerMetadata.getLedgerId(), 0, ledgerMetadata.getFirstTxId(),
        ledgerMetadata.getLastTxId(), ledgerMetadata.getLastTxId() == -1);
  } catch (LedgerHeaderCorruptException e) {
    LOG.warn("Log at ledger id" + ledgerMetadata.getLedgerId() +
        " has no valid header", e);
    return new FSEditLogLoader.EditLogValidation(0,
        HdfsConstants.INVALID_TXID, HdfsConstants.INVALID_TXID, true);
  }

  try {
    return FSEditLogLoader.validateEditLog(in);
  } finally {
    IOUtils.closeStream(in);
  }
}
 

import org.apache.hadoop.hdfs.server.namenode.FSEditLogLoader; //导入依赖的package包/类
long validateAndGetEndTxId(EditLogLedgerMetadata ledger, boolean fence)
    throws IOException {
  FSEditLogLoader.EditLogValidation val;
  if (!fence) {
    val = BookKeeperEditLogInputStream.validateEditLog(this, ledger);
  } else {
    val = BookKeeperEditLogInputStream.validateEditLog(
        new FencingLedgerHandleProvider(), ledger);
  }
  InjectionHandler.processEvent(InjectionEvent.BKJM_VALIDATELOGSEGMENT,
      val);
  if (val.getNumTransactions() == 0) {
    return HdfsConstants.INVALID_TXID; // Ledger is corrupt
  }
  return val.getEndTxId();
}
 

import org.apache.hadoop.hdfs.server.namenode.FSEditLogLoader; //导入依赖的package包/类
@Test
public void testFailoverRetryStandbyQuiesce() throws Exception {
  setUp("testFailoverRetryBlocksMisMatch", false);
  int totalBlocks = 50;
  DFSTestUtil.createFile(fs, new Path("/testFailoverRetryBlocksMisMatch"),
      (long) totalBlocks * 1024, (short) 3, System.currentTimeMillis());
  // This should shutdown the standby.
  cluster.getStandbyAvatar(0).avatar
      .quiesceStandby(FSEditLogLoader.TXID_IGNORE);
  while (!restartDone) {
    LOG.info("Waiting for restart..");
    Thread.sleep(1000);
  }
  try {
    tryConnect(cluster.getStandbyAvatar(0).avatar);
    fail("Did not throw exception");
  } catch (Exception e) {
    LOG.warn("Expected exception : ", e);
  }
}
 

import org.apache.hadoop.hdfs.server.namenode.FSEditLogLoader; //导入依赖的package包/类
URLLogInputStream(AsyncLogger logger, long firstTxId, int httpTimeout)
    throws LogHeaderCorruptException, IOException {
  log = new URLLog(logger, firstTxId, httpTimeout);
  fStream = log.getInputStream(0);
  
  lastValidTxId = log.getLastValidTxId();
  super.setIsInProgress(log.getIsInProgress());

  BufferedInputStream bin = new BufferedInputStream(fStream);  
  tracker = new FSEditLogLoader.PositionTrackingInputStream(bin);  
  DataInputStream in = new DataInputStream(tracker);

  try {
    logVersion = readLogVersion(in);
  } catch (EOFException eofe) {
    throw new LogHeaderCorruptException("No header found in log");
  }
  reader = new FSEditLogOp.Reader(in, logVersion);
  this.firstTxId = firstTxId;
  this.disabled = false;
  // set initial position (version is 4 bytes)
  this.currentPosition = tracker.getPos();
}
 

import org.apache.hadoop.hdfs.server.namenode.FSEditLogLoader; //导入依赖的package包/类
@Override
protected void _processEvent(InjectionEventI event, Object... args) {
  if (event == InjectionEvent.BKJM_STARTLOGSEGMENT) {
    ledgerForStartedSegment = (EditLogLedgerMetadata) args[0];
  } else if (event == InjectionEvent.BKJM_VALIDATELOGSEGMENT) {
    logValidation = (FSEditLogLoader.EditLogValidation) args[0];
  }
}
 

import org.apache.hadoop.hdfs.server.namenode.FSEditLogLoader; //导入依赖的package包/类
protected static TestAvatarCheckpointingHandler testQuiesceInterruption(
    InjectionEvent stopOnEvent, InjectionEvent waitUntilEvent, boolean scf,
    boolean testCancellation, boolean rollAfterQuiesce,
    boolean enableQJM) throws Exception {
  LOG.info("TEST Quiesce during checkpoint : " + stopOnEvent
      + " waiting on: " + waitUntilEvent);
  TestAvatarCheckpointingHandler h = new TestAvatarCheckpointingHandler(
      stopOnEvent, waitUntilEvent, scf);
  InjectionHandler.set(h);
  setUp(3, "testQuiesceInterruption", false, enableQJM); //simulate interruption, no ckpt failure   
  
  AvatarNode primary = cluster.getPrimaryAvatar(0).avatar;
  AvatarNode standby = cluster.getStandbyAvatar(0).avatar;
  createEdits(40);

  while (!h.receivedEvents.contains(stopOnEvent)) {
    LOG.info("Waiting for event : " + stopOnEvent);
    Thread.sleep(1000);
  }
  
  if (!enableQJM) {
  	standby.quiesceStandby(getCurrentTxId(primary)-1);
  	// only assert this for FileJournalManager.
  	// edits + SLS + ELS + SLS (checkpoint fails, but roll happened)
   assertEquals(43, getCurrentTxId(primary));
   
   // if quiesce happened before roll, the standby will be behind by 1 transaction
   // which will be reclaimed by opening the log after
   long extraTransaction = rollAfterQuiesce ? 1 : 0;
   assertEquals(getCurrentTxId(primary), getCurrentTxId(standby) + extraTransaction);
  } else {
  	standby.quiesceStandby(FSEditLogLoader.TXID_IGNORE);
  }
  
  // make sure the checkpoint indeed failed
  assertTrue(h.receivedEvents
      .contains(InjectionEvent.STANDBY_EXIT_CHECKPOINT_EXCEPTION));
  if (testCancellation) {
    assertTrue(h.receivedEvents
        .contains(InjectionEvent.SAVE_NAMESPACE_CONTEXT_EXCEPTION));
  }
  return h;
}