一、文件
上传：
[hadoop@hadoop001 ~]$ hdfs dfs -mkdir /blockrecover
[hadoop@hadoop001 ~]$ hdfs dfs -put data/genome-scores.csv /blockrecover
[hadoop@hadoop001 ~]$ hdfs dfs -ls /blockrecover
Found 1 items
-rw-r--r-- 3 hadoop hadoop 323544381 2019-08-21 18:48 /blockrecover/genome-scores.csv
校验健康状态:
[hadoop@hadoop001 ~]$ hdfs fsck /
Connecting to namenode via http://hadoop001:50070/fsck?ugi=hadoop&path=%2F
FSCK started by hadoop (auth:SIMPLE) from /192.168.174.121 for path / at Thu Aug 22 15:44:41 CST 2019
.Status: HEALTHY
Total size: 323544381 B
Total dirs: 10
Total files: 1
Total symlinks: 0
Total blocks (validated): 3 (avg. block size 107848127 B)
Minimally replicated blocks: 3 (100.0 %)
Over-replicated blocks: 0 (0.0 %)
Under-replicated blocks: 0 (0.0 %)
Mis-replicated blocks: 0 (0.0 %)
Default replication factor: 3
Average block replication: 3.0
Corrupt blocks: 0
Missing replicas: 0 (0.0 %)
Number of data-nodes: 3
Number of racks: 1
FSCK ended at Thu Aug 22 15:44:41 CST 2019 in 4 milliseconds
The filesystem under path '/' is HEALTHY
二、直接DN节点上删除文件一个block的一个副本(3副本）
删除块和meta文件：
[hadoop@hadoop002 subdir0]$ ll
total 318444
-rw-rw-r-- 1 hadoop hadoop 134217728 Aug 22 15:27 blk_1073741825
-rw-rw-r-- 1 hadoop hadoop 1048583 Aug 22 15:27 blk_1073741825_1001.meta
-rw-rw-r-- 1 hadoop hadoop 134217728 Aug 21 18:48 blk_1073741826
-rw-rw-r-- 1 hadoop hadoop 1048583 Aug 21 18:48 blk_1073741826_1002.meta
-rw-rw-r-- 1 hadoop hadoop 55108925 Aug 21 18:48 blk_1073741827
-rw-rw-r-- 1 hadoop hadoop 430547 Aug 21 18:48 blk_1073741827_1003.meta
[hadoop@hadoop002 subdir0]$ rm -rf blk_1073741825 blk_1073741825_1001.meta
[hadoop@hadoop002 subdir0]$ ll
total 186344
-rw-rw-r-- 1 hadoop hadoop 134217728 Aug 21 18:48 blk_1073741826
-rw-rw-r-- 1 hadoop hadoop 1048583 Aug 21 18:48 blk_1073741826_1002.meta
-rw-rw-r-- 1 hadoop hadoop 55108925 Aug 21 18:48 blk_1073741827
-rw-rw-r-- 1 hadoop hadoop 430547 Aug 21 18:48 blk_1073741827_1003.meta
直接重启HDFS，直接模拟损坏效果，然后fsck检查:
[hadoop@hadoop001 ~]$ hdfs fsck /
Connecting to namenode via http://hadoop002:50070/fsck?ugi=hadoop&path=%2F
FSCK started by hadoop (auth:SIMPLE) from /192.168.174.121 for path / at Thu Aug 22 15:49:54 CST 2019
.
/blockrecover/genome-scores.csv: Under replicated BP-1685056456-192.168.174.121-1566207286072:blk_1073741825_1001. Target Replicas is 3 but found 2 live replica(s), 0 decommissioned replica(s), 0 decommissioning replica(s).
Status: HEALTHY
Total size: 323544381 B
Total dirs: 10
Total files: 1
Total symlinks: 0
Total blocks (validated): 3 (avg. block size 107848127 B)
Minimally replicated blocks: 3 (100.0 %)
Over-replicated blocks: 0 (0.0 %)
Under-replicated blocks: 1 (33.333332 %)
Mis-replicated blocks: 0 (0.0 %)
Default replication factor: 3
Average block replication: 2.6666667
Corrupt blocks: 0
Missing replicas: 1 (11.111111 %)
Number of data-nodes: 3
Number of racks: 1
FSCK ended at Thu Aug 22 15:49:54 CST 2019 in 26 milliseconds
The filesystem under path '/' is HEALTHY
三、手动修复
[hadoop@hadoop001 ~]$ hdfs | grep debug
没有输出debug参数的任何信息结果！ 故hdfs命令帮助是没有debug的，但是确实有hdfs debug这个组合命令，切记。
#修复命令
[hadoop@hadoop001 ~]$ hdfs debug recoverLease -path /blockrecover/genome-scores.csv -retries 10
直接DN节点查看，block文件和meta文件恢复
[hadoop@hadoop002 subdir0]$ ll
total 318444
-rw-rw-r-- 1 hadoop hadoop 134217728 Aug 22 15:50 blk_1073741825
-rw-rw-r-- 1 hadoop hadoop 1048583 Aug 22 15:50 blk_1073741825_1001.meta
-rw-rw-r-- 1 hadoop hadoop 134217728 Aug 21 18:48 blk_1073741826
-rw-rw-r-- 1 hadoop hadoop 1048583 Aug 21 18:48 blk_1073741826_1002.meta
-rw-rw-r-- 1 hadoop hadoop 55108925 Aug 21 18:48 blk_1073741827
-rw-rw-r-- 1 hadoop hadoop 430547 Aug 21 18:48 blk_1073741827_1003.meta
四、自动修复
当数据块损坏后，DN节点执行directoryscan操作之前，都不会发现损坏；
也就是directoryscan操作是间隔6h
dfs.datanode.directoryscan.interval : 21600
在DN向NN进行blockreport前，都不会恢复数据块;
也就是blockreport操作是间隔6h
dfs.blockreport.intervalMsec : 21600000
当NN收到blockreport才会进⾏行行恢复操作
五、直接在一个block块副本写入脏数据，造成副本损坏
[hadoop@hadoop002 subdir0]$ ll
total 318448
-rw-rw-r-- 1 hadoop hadoop 134217728 Aug 22 17:34 blk_1073741828
-rw-rw-r-- 1 hadoop hadoop 1048583 Aug 22 17:34 blk_1073741828_1004.meta
-rw-rw-r-- 1 hadoop hadoop 134217728 Aug 22 17:35 blk_1073741829
-rw-rw-r-- 1 hadoop hadoop 1048583 Aug 22 17:35 blk_1073741829_1005.meta
-rw-rw-r-- 1 hadoop hadoop 55108925 Aug 22 17:35 blk_1073741830
-rw-rw-r-- 1 hadoop hadoop 430547 Aug 22 17:35 blk_1073741830_1006.meta
[hadoop@hadoop002 subdir0]$ echo "gfdgfdgdf" >> blk_1073741830
直接重启HDFS，直接模拟损坏效果，然后fsck检查:
[hadoop@hadoop001 logs]$ hdfs fsck /
Connecting to namenode via http://hadoop001:50070/fsck?ugi=hadoop&path=%2F
FSCK started by hadoop (auth:SIMPLE) from /192.168.174.121 for path / at Fri Aug 23 09:05:39 CST 2019
.
/blockrecover/genome-scores.csv: Under replicated BP-1685056456-192.168.174.121-1566207286072:blk_1073741830_1006. Target Replicas is 3 but found 2 live replica(s), 0 decommissioned replica(s), 0 decommissioning replica(s).
Status: HEALTHY
Total size: 323544381 B
Total dirs: 10
Total files: 1
Total symlinks: 0
Total blocks (validated): 3 (avg. block size 107848127 B)
Minimally replicated blocks: 3 (100.0 %)
Over-replicated blocks: 0 (0.0 %)
Under-replicated blocks: 1 (33.333332 %)
Mis-replicated blocks: 0 (0.0 %)
Default replication factor: 3
Average block replication: 2.6666667
Corrupt blocks: 0
Missing replicas: 1 (11.111111 %)
Number of data-nodes: 3
Number of racks: 1
FSCK ended at Fri Aug 23 09:05:39 CST 2019 in 59 milliseconds
The filesystem under path '/' is HEALTHY
定位到Block损坏的副本位置
[hadoop@hadoop001 ~]$ hdfs fsck /blockrecover/genome-scores.csv -files -locations -blocks -racks
Connecting to namenode via http://hadoop001:50070/fsck?ugi=hadoop&files=1&locations=1&blocks=1&racks=1&path=%2Fblockrecover%2Fgenome-scores.csv
FSCK started by hadoop (auth:SIMPLE) from /192.168.174.121 for path /blockrecover/genome-scores.csv at Fri Aug 23 09:57:52 CST 2019
/blockrecover/genome-scores.csv 323544381 bytes, 3 block(s): Under replicated BP-1685056456-192.168.174.121-1566207286072:blk_1073741830_1006. Target Replicas is 3 but found 2 live replica(s), 0 decommissioned replica(s), 0 decommissioning replica(s).
0. BP-1685056456-192.168.174.121-1566207286072:blk_1073741828_1004 len=134217728 Live_repl=3 [/default-rack/192.168.174.123:50010, /default-rack/192.168.174.121:50010, /default-rack/192.168.174.122:50010]
1. BP-1685056456-192.168.174.121-1566207286072:blk_1073741829_1005 len=134217728 Live_repl=3 [/default-rack/192.168.174.123:50010, /default-rack/192.168.174.121:50010, /default-rack/192.168.174.122:50010]
2. BP-1685056456-192.168.174.121-1566207286072:blk_1073741830_1006 len=55108925 Live_repl=2 [/default-rack/192.168.174.123:50010, /default-rack/192.168.174.121:50010]
Status: HEALTHY
Total size: 323544381 B
Total dirs: 0
Total files: 1
Total symlinks: 0
Total blocks (validated): 3 (avg. block size 107848127 B)
Minimally replicated blocks: 3 (100.0 %)
Over-replicated blocks: 0 (0.0 %)
Under-replicated blocks: 1 (33.333332 %)
Mis-replicated blocks: 0 (0.0 %)
Default replication factor: 3
Average block replication: 2.6666667
Corrupt blocks: 0
Missing replicas: 1 (11.111111 %)
Number of data-nodes: 3
Number of racks: 1
FSCK ended at Fri Aug 23 09:57:52 CST 2019 in 2 milliseconds
The filesystem under path '/blockrecover/genome-scores.csv' is HEALTHY
结果:没办法定位到损坏副本的位置
解决方式：
- 手动找到损坏副本的位置,删除对应的block文件和meta文件,然后执行
hdfs debug recoverLease -path /blockrecover/genome-scores.csv -retries 10- 先把文件get下载，然后hdfs删除，再对应上传
六、总结
生产上本人一般倾向于使用 手动修复方式.
当然还可以先把文件get下载，然后hdfs删除，再对应上传。