hadoop JournalManager 源码

haddop JournalManager 代码

文件路径：/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/JournalManager.java

/**
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.apache.hadoop.hdfs.server.namenode;

import java.io.Closeable;
import java.io.IOException;

import org.apache.hadoop.classification.InterfaceAudience;
import org.apache.hadoop.classification.InterfaceStability;
import org.apache.hadoop.hdfs.server.common.Storage;
import org.apache.hadoop.hdfs.server.common.Storage.FormatConfirmable;
import org.apache.hadoop.hdfs.server.common.StorageInfo;
import org.apache.hadoop.hdfs.server.protocol.NamespaceInfo;

/**
 * A JournalManager is responsible for managing a single place of storing
 * edit logs. It may correspond to multiple files, a backup node, etc.
 * Even when the actual underlying storage is rolled, or failed and restored,
 * each conceptual place of storage corresponds to exactly one instance of
 * this class, which is created when the EditLog is first opened.
 */
@InterfaceAudience.Private
@InterfaceStability.Evolving
public interface JournalManager extends Closeable, FormatConfirmable,
    LogsPurgeable {

  /**
   * Format the underlying storage, removing any previously
   * stored data.
   */
  void format(NamespaceInfo ns, boolean force) throws IOException;

  /**
   * Begin writing to a new segment of the log stream, which starts at
   * the given transaction ID.
   */
  EditLogOutputStream startLogSegment(long txId, int layoutVersion)
      throws IOException;

  /**
   * Mark the log segment that spans from firstTxId to lastTxId
   * as finalized and complete.
   */
  void finalizeLogSegment(long firstTxId, long lastTxId) throws IOException;

  /**
   * Set the amount of memory that this stream should use to buffer edits
   */
  void setOutputBufferCapacity(int size);

  /**
   * Recover segments which have not been finalized.
   */
  void recoverUnfinalizedSegments() throws IOException;
  
  /**
   * Perform any steps that must succeed across all JournalManagers involved in
   * an upgrade before proceeding onto the actual upgrade stage. If a call to
   * any JM's doPreUpgrade method fails, then doUpgrade will not be called for
   * any JM.
   */
  void doPreUpgrade() throws IOException;
  
  /**
   * Perform the actual upgrade of the JM. After this is completed, the NN can
   * begin to use the new upgraded metadata. This metadata may later be either
   * finalized or rolled back to the previous state.
   * 
   * @param storage info about the new upgraded versions.
   */
  void doUpgrade(Storage storage) throws IOException;
  
  /**
   * Finalize the upgrade. JMs should purge any state that they had been keeping
   * around during the upgrade process. After this is completed, rollback is no
   * longer allowed.
   */
  void doFinalize() throws IOException;
  
  /**
   * Return true if this JM can roll back to the previous storage state, false
   * otherwise. The NN will refuse to run the rollback operation unless at least
   * one JM or fsimage storage directory can roll back.
   * 
   * @param storage the storage info for the current state
   * @param prevStorage the storage info for the previous (unupgraded) state
   * @param targetLayoutVersion the layout version we intend to roll back to
   * @return true if this JM can roll back, false otherwise.
   */
  boolean canRollBack(StorageInfo storage, StorageInfo prevStorage,
      int targetLayoutVersion) throws IOException;
  
  /**
   * Perform the rollback to the previous FS state. JMs which do not need to
   * roll back their state should just return without error.
   */
  void doRollback() throws IOException;

  /**
   * Discard the segments whose first txid is {@literal >=} the given txid.
   * @param startTxId The given txid should be right at the segment boundary, 
   * i.e., it should be the first txid of some segment, if segment corresponding
   * to the txid exists.
   */
  void discardSegments(long startTxId) throws IOException;

  /**
   * @return the CTime of the journal manager.
   */
  long getJournalCTime() throws IOException;

  /**
   * Close the journal manager, freeing any resources it may hold.
   */
  @Override
  void close() throws IOException;
  
  /** 
   * Indicate that a journal is cannot be used to load a certain range of 
   * edits.
   * This exception occurs in the case of a gap in the transactions, or a
   * corrupt edit file.
   */
  public static class CorruptionException extends IOException {
    static final long serialVersionUID = -4687802717006172702L;
    
    public CorruptionException(String reason) {
      super(reason);
    }
  }

}

相关信息

hadoop 源码目录

相关文章

hadoop AclEntryStatusFormat 源码

hadoop AclFeature 源码

hadoop AclStorage 源码

hadoop AclTransformation 源码

hadoop AuditLogger 源码

hadoop BackupImage 源码

hadoop BackupJournalManager 源码

hadoop BackupNode 源码

hadoop BackupState 源码

hadoop CacheManager 源码