一.崩溃原因

搭建的是一个hadoop测试集群，所以将数据备份参数设置为dfs.replication=1,这样如果有一台datanode损坏的话，数据就会失去。但不幸的是，刚好就有一台机器由于负载过高，导致数据操坏。进而后面需要重启整个hadoop集群,重启后启动namenode启动不了。报如下错误:

 

FSNamesystem initialization failed saveLeases found path    /tmp/xxx/aaa.txt but no matching entry in namespace.

FSNamesystem initialization failed saveLeases found path	/tmp/xxx/aaa.txt but no matching entry in namespace.

 

二.修复namenode 

 

hadoop 集群崩溃了. 导致namenode启动不了.

 

1. 删除 namenode主节点的metadata配置目录

rm -fr /data/hadoop-tmp/hadoop-hadoop/dfs/name

 

2. 启动secondnamenode

使用start-all.sh命令启动secondnamenode,namenode的启动不了不管

 

3. 从secondnamenode恢复

使用命令: hadoop namenode -importCheckpoint

 

 

恢复过程中，发现数据文件有些已经损坏(因为dfs.replication=1),所以一直无法退出安全模式(safemode),一直报如下提示:

 

The ratio of reported blocks 0.8866 has not reached the threshold 0.9990. Safe mode will be turned off automatically.

The ratio of reported blocks 0.8866 has not reached the threshold 0.9990. Safe mode will be turned off automatically.

 

 

4.强制退出safemode

 

 

hadoop dfsadmin -safemode leave

hadoop dfsadmin -safemode leave

 

最后启动成功，查看hdfs网页报警告信息:

 

 

WARNING : There are about 257 missing blocks. Please check the log or run fsck.

WARNING : There are about 257 missing blocks. Please check the log or run fsck.

 

 

5.检查损坏的hdfs文件列表

 

使用命令可以打印出损坏的文件列表: 

 

./hadoop fsck /

./hadoop fsck /

 打印结果:

 

 

 

/user/hive/warehouse/pay_consume_orgi/dt=2011-06-28/consume_2011-06-28.sql: MISSING 1 blocks of total size 1250990 B..
/user/hive/warehouse/pay_consume_orgi/dt=2011-06-29/consume_2011-06-29.sql: CORRUPT block blk_977550919055291594

/user/hive/warehouse/pay_consume_orgi/dt=2011-06-29/consume_2011-06-29.sql: MISSING 1 blocks of total size 1307147 B..................Status: CORRUPT
 Total size:    235982871209 B
 Total dirs:    1213
 Total files:   1422
 Total blocks (validated):      4550 (avg. block size 51864367 B)
  ********************************
  CORRUPT FILES:        277
  MISSING BLOCKS:       509
  MISSING SIZE:         21857003415 B
  CORRUPT BLOCKS:       509
  ********************************

/user/hive/warehouse/pay_consume_orgi/dt=2011-06-28/consume_2011-06-28.sql: MISSING 1 blocks of total size 1250990 B../user/hive/warehouse/pay_consume_orgi/dt=2011-06-29/consume_2011-06-29.sql: CORRUPT block blk_977550919055291594/user/hive/warehouse/pay_consume_orgi/dt=2011-06-29/consume_2011-06-29.sql: MISSING 1 blocks of total size 1307147 B..................Status: CORRUPT Total size:    235982871209 B Total dirs:    1213 Total files:   1422 Total blocks (validated):      4550 (avg. block size 51864367 B)  ********************************  CORRUPT FILES:        277  MISSING BLOCKS:       509  MISSING SIZE:         21857003415 B  CORRUPT BLOCKS:       509  ********************************

没有冗余备份,只能删除损坏的文件,使用命令:

./hadoop fsck --delete

./hadoop fsck --delete

 

 

三.总结

 

一定需要将你的secondnamenode及namenode分开在不同两台机器运行，增加namenode的容错性。以便在集群崩溃时可以从secondnamenode恢复数据.