HDFS文件误删怎么办,一招教你恢复回来,再也不用担心删库跑路了

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本文基于 Hadoop3.1.2版本讲解

HDFS 文件删除过程

下面是hdfs删除路径的方法,源码路径org.apache.hadoop.hdfs.server.namenode.FSNamesystem.delete() 

/**
   * Remove the indicated file from namespace.
   * 
   * @see ClientProtocol#delete(String, boolean) for detailed description and 
   * description of exceptions
   */
    boolean delete(String src, boolean recursive, boolean logRetryCache)
      throws IOException {
    waitForLoadingFSImage();
    BlocksMapUpdateInfo toRemovedBlocks = null;
    writeLock();
    boolean ret = false;
    try {
      checkOperation(OperationCategory.WRITE);
      checkNameNodeSafeMode("Cannot delete " + src);
      toRemovedBlocks = FSDirDeleteOp.delete(        // @1
          this, src, recursive, logRetryCache);
      ret = toRemovedBlocks != null;
    } catch (AccessControlException e) {
      logAuditEvent(false, "delete", src);
      throw e;
    } finally {
      writeUnlock();
    }
    getEditLog().logSync();
    if (toRemovedBlocks != null) {
      removeBlocks(toRemovedBlocks);   // @2
    }
    logAuditEvent(true, "delete", src);
    return ret;
  }

代码@1里面做了三件比较重要的事

①从 NameNode 维护的的目录树里面删除路径,这也是为什么执行删除操作之后就无法再通过hdfs dfs -ls xxx 或其它 api 方式再查看到路径的根本原因(拒绝需要被删除的文件的外部访问)

②找出被删路径关联的 block 信息,每个文件包含多个 block 块,分布在各个 DataNode,此时并未真正物理删除 DataNode 上物理磁盘上的block块

③记录删除日志到editlog(这一步也很重要,甚至是后面恢复数据的关键)

代码@2把将要删除的block信息添加到org.apache.hadoop.hdfs.server.blockmanagement.BlockManager 里面维护的 InvalidateBlocks 对象中,InvalidateBlocks 专门用于保存等待删除的数据块副本

以上步骤并未涉及真正的物理删除的操作

BlockManager

BlockManager 管理了hdfs block 的生命周期并且维护在 Hadoop 集群中的块相关的信息,包括快的上报、复制、删除、监控、标记等等一系列功能。

BlockManager 中有个方法 invalidateWorkForOneNode() 专门用于定时删除 InvalidateBlocks 中存储的待删除的快,此方法会在 NameNode 启动时在 BlockManager 的内部线程类ReplicationMonitor 定时轮循把要删除的块放入 DatanodeDescriptor 中的逻辑,方法的调用路径如下:

org.apache.hadoop.hdfs.server.namenode.NameNode#initialize(Configuration conf) 
 org.apache.hadoop.hdfs.server.namenode.NameNode#startCommonServices(Configuration conf)
  org.apache.hadoop.hdfs.server.namenode.FSNamesystem#startCommonServices(Configuration conf, HAContext haContext)
   org.apache.hadoop.hdfs.server.blockmanagement.BlockManager#activate(Configuration conf)
    org.apache.hadoop.hdfs.server.blockmanagement.BlockManager.ReplicationMonitor#run()
     org.apache.hadoop.hdfs.server.blockmanagement.BlockManager#computeDatanodeWork()
      org.apache.hadoop.hdfs.server.blockmanagement.BlockManager#computeDatanodeWorkcomputeInvalidateWork(int nodesToProcess)
       org.apache.hadoop.hdfs.server.blockmanagement.BlockManager#invalidateWorkForOneNode(DatanodeInfo dn)
        org.apache.hadoop.hdfs.server.blockmanagement.InvalidateBlocks#invalidateWork(final DatanodeDescriptor dn)

BlockManager 维护了 InvalidateBlocks,存放了待删除的 block,BlockManager 在 NameNode 启动时会单独启动一个线程,定时把要删除的块信息放入 InvalidateBlocks 中,每次会从InvalidateBlocks 队列中为每个 DataNode 取出 blockInvalidateLimit(由配置项dfs.block.invalidate.limit,默认1000)个块逻辑在 BlockManager.computeInvalidateWork() 方法里会把要删除的块信息放入 DatanodeDescriptor 中的 invalidateBlocks 数组,DatanodeManager 再通过 DataNode 与NameNode 心跳时,构建删除块的指令集,NameNode 再把指令下发给DataNode,心跳由 DatanodeProtocol 调用,方法的调用路径如下:

org.apache.hadoop.hdfs.server.protocol.DatanodeProtocol#sendHeartbeat()
 org.apache.hadoop.hdfs.server.namenode.NameNodeRpcServer#sendHeartbeat()
  org.apache.hadoop.hdfs.server.namenode.FSNamesystem#handleHeartbeat()
   org.apache.hadoop.hdfs.server.blockmanagement.DatanodeManager#handleHeartbeat()

DatanodeManager.handleHeartbeat() 中构建删除的指令给 DataNode,待 NameNode 发送的代码如下: 

  /** Handle heartbeat from datanodes. */
  public DatanodeCommand[] handleHeartbeat(DatanodeRegistration nodeReg,
      StorageReport[] reports, final String blockPoolId,
      long cacheCapacity, long cacheUsed, int xceiverCount, 
      int maxTransfers, int failedVolumes,
      VolumeFailureSummary volumeFailureSummary,
      @Nonnull SlowPeerReports slowPeers,
      @Nonnull SlowDiskReports slowDisks) throws IOException {
    final DatanodeDescriptor nodeinfo;
    try {
      nodeinfo = getDatanode(nodeReg);
    } catch (UnregisteredNodeException e) {
      return new DatanodeCommand[]{RegisterCommand.REGISTER};
    }

    // Check if this datanode should actually be shutdown instead.
    if (nodeinfo != null && nodeinfo.isDisallowed()) {
      setDatanodeDead(nodeinfo);
      throw new DisallowedDatanodeException(nodeinfo);
    }

    if (nodeinfo == null || !nodeinfo.isRegistered()) {
      return new DatanodeCommand[]{RegisterCommand.REGISTER};
    }
    heartbeatManager.updateHeartbeat(nodeinfo, reports, cacheCapacity,
        cacheUsed, xceiverCount, failedVolumes, volumeFailureSummary);

    // If we are in safemode, do not send back any recovery / replication
    // requests. Don't even drain the existing queue of work.
    if (namesystem.isInSafeMode()) {
      return new DatanodeCommand[0];
    }

    // block recovery command
    final BlockRecoveryCommand brCommand = getBlockRecoveryCommand(blockPoolId,
        nodeinfo);
    if (brCommand != null) {
      return new DatanodeCommand[]{brCommand};
    }

    final List<DatanodeCommand> cmds = new ArrayList<>();
    // Allocate _approximately_ maxTransfers pending tasks to DataNode.
    // NN chooses pending tasks based on the ratio between the lengths of
    // replication and erasure-coded block queues.
    int totalReplicateBlocks = nodeinfo.getNumberOfReplicateBlocks();
    int totalECBlocks = nodeinfo.getNumberOfBlocksToBeErasureCoded();
    int totalBlocks = totalReplicateBlocks + totalECBlocks;
    if (totalBlocks > 0) {
      int numReplicationTasks = (int) Math.ceil(
          (double) (totalReplicateBlocks * maxTransfers) / totalBlocks);
      int numECTasks = (int) Math.ceil(
          (double) (totalECBlocks * maxTransfers) / totalBlocks);

      if (LOG.isDebugEnabled()) {
        LOG.debug("Pending replication tasks: " + numReplicationTasks
            + " erasure-coded tasks: " + numECTasks);
      }
      // check pending replication tasks
      List<BlockTargetPair> pendingList = nodeinfo.getReplicationCommand(
          numReplicationTasks);
      if (pendingList != null && !pendingList.isEmpty()) {
        cmds.add(new BlockCommand(DatanodeProtocol.DNA_TRANSFER, blockPoolId,
            pendingList));
      }
      // check pending erasure coding tasks
      List<BlockECReconstructionInfo> pendingECList = nodeinfo
          .getErasureCodeCommand(numECTasks);
      if (pendingECList != null && !pendingECList.isEmpty()) {
        cmds.add(new BlockECReconstructionCommand(
            DNA_ERASURE_CODING_RECONSTRUCTION, pendingECList));
      }
    }

    // check block invalidation
    Block[] blks = nodeinfo.getInvalidateBlocks(blockInvalidateLimit);
    if (blks != null) {
      cmds.add(new BlockCommand(DatanodeProtocol.DNA_INVALIDATE, blockPoolId,
          blks));
    }
    // cache commands
    addCacheCommands(blockPoolId, nodeinfo, cmds);
    // key update command
    blockManager.addKeyUpdateCommand(cmds, nodeinfo);

    // check for balancer bandwidth update
    if (nodeinfo.getBalancerBandwidth() > 0) {
      cmds.add(new BalancerBandwidthCommand(nodeinfo.getBalancerBandwidth()));
      // set back to 0 to indicate that datanode has been sent the new value
      nodeinfo.setBalancerBandwidth(0);
    }

    if (slowPeerTracker != null) {
      final Map<String, Double> slowPeersMap = slowPeers.getSlowPeers();
      if (!slowPeersMap.isEmpty()) {
        if (LOG.isDebugEnabled()) {
          LOG.debug("DataNode " + nodeReg + " reported slow peers: " +
              slowPeersMap);
        }
        for (String slowNodeId : slowPeersMap.keySet()) {
          slowPeerTracker.addReport(slowNodeId, nodeReg.getIpcAddr(false));
        }
      }
    }

    if (slowDiskTracker != null) {
      if (!slowDisks.getSlowDisks().isEmpty()) {
        if (LOG.isDebugEnabled()) {
          LOG.debug("DataNode " + nodeReg + " reported slow disks: " +
              slowDisks.getSlowDisks());
        }
        slowDiskTracker.addSlowDiskReport(nodeReg.getIpcAddr(false), slowDisks);
      }
    }

    if (!cmds.isEmpty()) {
      return cmds.toArray(new DatanodeCommand[cmds.size()]);
    }

    return new DatanodeCommand[0];
  }

定时轮循+limit 1000个块删除的特性决定了hdfs删除数据并不会立即真正的执行物理删除,并且一次删除的数量也有限,所以出现误删操作需要立即停止HDFS,虽然有的数据在轮循中已被删除,所以事发后停止HDFS集群越早,被删的数据越少,损失越小!

EditLog

EditLog记录了hdfs操作的每一条日志记录,包括当然包括删除,我们所熟知的文件操作类型只有增、删、改,但是在 HDFS 的领域里,远远不止这些操作,我们看看 EditLog 操作类型的枚举类org.apache.hadoop.hdfs.server.namenode.FSEditLogOpCodes
 

/**
 * 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 org.apache.hadoop.classification.InterfaceAudience;
import org.apache.hadoop.classification.InterfaceStability;
import org.apache.hadoop.hdfs.server.namenode.FSEditLogOp.*;

/**
 * Op codes for edits file
 */
@InterfaceAudience.Private
@InterfaceStability.Unstable
public enum FSEditLogOpCodes {
  // last op code in file
  OP_ADD                        ((byte)  0, AddOp.class),
  // deprecated operation
  OP_RENAME_OLD                 ((byte)  1, RenameOldOp.class),
  OP_DELETE                     ((byte)  2, DeleteOp.class),
  OP_MKDIR                      ((byte)  3, MkdirOp.class),
  OP_SET_REPLICATION            ((byte)  4, SetReplicationOp.class),
  @Deprecated OP_DATANODE_ADD   ((byte)  5), // obsolete
  @Deprecated OP_DATANODE_REMOVE((byte)  6), // obsolete
  OP_SET_PERMISSIONS            ((byte)  7, SetPermissionsOp.class),
  OP_SET_OWNER                  ((byte)  8, SetOwnerOp.class),
  OP_CLOSE                      ((byte)  9, CloseOp.class),
  OP_SET_GENSTAMP_V1            ((byte) 10, SetGenstampV1Op.class),
  OP_SET_NS_QUOTA               ((byte) 11, SetNSQuotaOp.class), // obsolete
  OP_CLEAR_NS_QUOTA             ((byte) 12, ClearNSQuotaOp.class), // obsolete
  OP_TIMES                      ((byte) 13, TimesOp.class), // set atime, mtime
  OP_SET_QUOTA                  ((byte) 14, SetQuotaOp.class),
  // filecontext rename
  OP_RENAME                     ((byte) 15, RenameOp.class),
  // concat files
  OP_CONCAT_DELETE              ((byte) 16, ConcatDeleteOp.class),
  OP_SYMLINK                    ((byte) 17, SymlinkOp.class),
  OP_GET_DELEGATION_TOKEN       ((byte) 18, GetDelegationTokenOp.class),
  OP_RENEW_DELEGATION_TOKEN     ((byte) 19, RenewDelegationTokenOp.class),
  OP_CANCEL_DELEGATION_TOKEN    ((byte) 20, CancelDelegationTokenOp.class),
  OP_UPDATE_MASTER_KEY          ((byte) 21, UpdateMasterKeyOp.class),
  OP_REASSIGN_LEASE             ((byte) 22, ReassignLeaseOp.class),
  OP_END_LOG_SEGMENT            ((byte) 23, EndLogSegmentOp.class),
  OP_START_LOG_SEGMENT          ((byte) 24, StartLogSegmentOp.class),
  OP_UPDATE_BLOCKS              ((byte) 25, UpdateBlocksOp.class),
  OP_CREATE_SNAPSHOT            ((byte) 26, CreateSnapshotOp.class),
  OP_DELETE_SNAPSHOT            ((byte) 27, DeleteSnapshotOp.class),
  OP_RENAME_SNAPSHOT            ((byte) 28, RenameSnapshotOp.class),
  OP_ALLOW_SNAPSHOT             ((byte) 29, AllowSnapshotOp.class),
  OP_DISALLOW_SNAPSHOT          ((byte) 30, DisallowSnapshotOp.class),
  OP_SET_GENSTAMP_V2            ((byte) 31, SetGenstampV2Op.class),
  OP_ALLOCATE_BLOCK_ID          ((byte) 32, AllocateBlockIdOp.class),
  OP_ADD_BLOCK                  ((byte) 33, AddBlockOp.class),
  OP_ADD_CACHE_DIRECTIVE        ((byte) 34, AddCacheDirectiveInfoOp.class),
  OP_REMOVE_CACHE_DIRECTIVE     ((byte) 35, RemoveCacheDirectiveInfoOp.class),
  OP_ADD_CACHE_POOL             ((byte) 36, AddCachePoolOp.class),
  OP_MODIFY_CACHE_POOL          ((byte) 37, ModifyCachePoolOp.class),
  OP_REMOVE_CACHE_POOL          ((byte) 38, RemoveCachePoolOp.class),
  OP_MODIFY_CACHE_DIRECTIVE     ((byte) 39, ModifyCacheDirectiveInfoOp.class),
  OP_SET_ACL                    ((byte) 40, SetAclOp.class),
  OP_ROLLING_UPGRADE_START      ((byte) 41, RollingUpgradeStartOp.class),
  OP_ROLLING_UPGRADE_FINALIZE   ((byte) 42, RollingUpgradeFinalizeOp.class),
  OP_SET_XATTR                  ((byte) 43, SetXAttrOp.class),
  OP_REMOVE_XATTR               ((byte) 44, RemoveXAttrOp.class),
  OP_SET_STORAGE_POLICY         ((byte) 45, SetStoragePolicyOp.class),
  OP_TRUNCATE                   ((byte) 46, TruncateOp.class),
  OP_APPEND                     ((byte) 47, AppendOp.class),
  OP_SET_QUOTA_BY_STORAGETYPE   ((byte) 48, SetQuotaByStorageTypeOp.class),
  OP_ADD_ERASURE_CODING_POLICY  ((byte) 49, AddErasureCodingPolicyOp.class),
  OP_ENABLE_ERASURE_CODING_POLICY((byte) 50, EnableErasureCodingPolicyOp.class),
  OP_DISABLE_ERASURE_CODING_POLICY((byte) 51,
      DisableErasureCodingPolicyOp.class),
  OP_REMOVE_ERASURE_CODING_POLICY((byte) 52, RemoveErasureCodingPolicyOp.class),

  // Note that the current range of the valid OP code is 0~127
  OP_INVALID                    ((byte) -1);

  private final byte opCode;
  private final Class<? extends FSEditLogOp> opClass;

  /**
   * Constructor
   *
   * @param opCode byte value of constructed enum
   */
  FSEditLogOpCodes(byte opCode) {
    this(opCode, null);
  }

  FSEditLogOpCodes(byte opCode, Class<? extends FSEditLogOp> opClass) {
    this.opCode = opCode;
    this.opClass = opClass;
  }

  /**
   * return the byte value of the enum
   *
   * @return the byte value of the enum
   */
  public byte getOpCode() {
    return opCode;
  }

  public Class<? extends FSEditLogOp> getOpClass() {
    return opClass;
  }

  private static final FSEditLogOpCodes[] VALUES;
  
  static {
    byte max = 0;
    for (FSEditLogOpCodes code : FSEditLogOpCodes.values()) {
      if (code.getOpCode() > max) {
        max = code.getOpCode();
      }
    }
    VALUES = new FSEditLogOpCodes[max + 1];
    for (FSEditLogOpCodes code : FSEditLogOpCodes.values()) {
      if (code.getOpCode() >= 0) {
        VALUES[code.getOpCode()] = code;
      }
    }
  }

  /**
   * Converts byte to FSEditLogOpCodes enum value
   *
   * @param opCode get enum for this opCode
   * @return enum with byte value of opCode
   */
  public static FSEditLogOpCodes fromByte(byte opCode) {
    if (opCode >= 0 && opCode < VALUES.length) {
      return VALUES[opCode];
    }
    return opCode == -1 ? OP_INVALID : null;
  }
}

总计54种操作类型!打破了人们印象中文件只有增删改读的几种操作。在hadoop的配置参数dfs.namenode.name.dir可以找到路径

 这里EditLog文件是序列化后的二进制文件不能直接查看,hdfs自带了解析的命令,可以解析成xml明文格式

hdfs oev -i edits_0000000000035854978-0000000000035906741 -o edits.xml

对 hdfs 的每一个操作都会记录一串 RECORD,RECORD 里面不同的操作包含的字段属性也不同,但是所有操作都具备的属性是 OPCODE,对应上面的枚举类org.apache.hadoop.hdfs.server.namenode.FSEditLogOpCodes中的操作

hdfs元数据的加载

hdfs 启动时,NameNode 会加载 Fsimage,Fsimage 记录了 hdfs 现有的全量的路径信息,启动过程中仅仅加载 Fsimage?这句话不完全正确!启动的同时,还会加载未被合并成 fsimage 的EditLog。关于 fsimage 具体细节这里不展开。举个栗子:

假设Hadoop 3分钟checkpoint一次生成Fsimage文件,EditLog 1分钟生成一个文件,下面是依次生成的文件:
 

fsimage_1
editlog_1
editlog_2
editlog_3
fsimage_2
editlog_4
editlog_5

当NameNode启动时,会加载后缀时间戳最大的那个fsimage文件和它后面产生的editlog文件,也就是会加载fsimage_2、editlog_4、editlog_5进NameNode内存。

恢复方法

假设我们执行 hdfs dfs -rmr xxx 命令的操作记录在了 editlog_5 上面,那么,重启 NameNode 后,我们查看hdfs无法再查看到xxx路径,如果我们把fsimage_2删掉,NameNode则会加载fsimage_1、editlog_1、editlog_2,此时的元数据里面xxx还未被删除,如果此时DataNode未物理删除block,则数据可以恢复,但是editlog_4、editlog_5对应的hdfs操作会丢失。有没有更好的方法呢?

方案一:

删掉 fsimage_2,从上一次 checkpoint 的地方也就是 fsimage_1 恢复,我们集群的实际配置,是一个小时生成一次 fsimage 文件,也就是说,这种恢复方案会导致近一小时 hdfs 新增的文件全部丢失,这一个小时不知道发生了多少事情,可想而知的后果是恢复之后一堆报错,显然不是最好的方案

方案二:

修改editlog_5,把删除xxx那条操作改成其它安全的操作类型,这样重启NameNode后,又可以看到这个路径。

步骤:

  • 关闭HDFS集群

  • 解析editlog

    找到删除操作时间点范围内所属的editlog文件,解析

    hdfs oev -i edits_0000000000000000336-0000000000000000414 -o edits.xml

    查看editlog.xml,执行删除操作的日志已经记录在里面了

  • 替换删除操作

        把OP_DELETE操作替换成比较安全的操作,例如

<RECORD>
    <OPCODE>OP_DELETE</OPCODE>
    <DATA>
      <TXID>374</TXID>
      <LENGTH>0</LENGTH>
      <PATH>/hbase/oldWALs/test%2C16020%2C1630456996531.1630464212306</PATH>
      <TIMESTAMP>1630724840046</TIMESTAMP>
      <RPC_CLIENTID>d1e2ae59-ba0c-4385-87d4-4da3d9ec019b</RPC_CLIENTID>
      <RPC_CALLID>1049</RPC_CALLID>
    </DATA>
  </RECORD>

注意:只能改变OPCODE,其他不能修改!!!

  • 反解析成editlog

# 反解析更改后的xml文件成editlog
hdfs oev -i editlog.xml -o edits_0000000000000000336-0000000000000000414.tmp -p binary
# 重命名掉之前的editlog
mv edits_0000000000000000336-0000000000000000414 edits_0000000000000000336-0000000000000000414.bak
# 替换反解析后的editlog
mv edits_0000000000000000336-0000000000000000414.tmp edits_0000000000000000336-0000000000000000414

  • 使用 scp 将修改后的 editlog 同步到其他 JournalNode 节点
  • 重启 HDFS,完成文件恢复

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