Jeff Field created HDFS-10788:
---------------------------------
Summary: fsck NullPointerException when it encounters corrupt
replicas
Key: HDFS-10788
URL: https://issues.apache.org/jira/browse/HDFS-10788
Project: Hadoop HDFS
Issue Type: Bug
Components: namenode
Affects Versions: 2.6.0
Environment: 2.6.0-cdh5.5.2 is the HDFS version from the CDH build
this cluster is running.
Reporter: Jeff Field
Somehow (I haven't found root cause yet) we ended up with blocks that have
corrupt replicas where the replica count is inconsistent between the blockmap
and the corrupt replicas map. If we try to hdfs fsck any parent directory that
has a child with one of these blocks, fsck will exit with something like this:
{code}
$ hdfs fsck /path/to/parent/dir/ | egrep -v '^\.+$'
Connecting to namenode via http://mynamenode:50070
FSCK started by bot-hadoop (auth:KERBEROS_SSL) from /10.97.132.43 for path
/path/to/parent/dir/ at Tue Aug 23 20:34:58 UTC 2016
.........................................................................FSCK
ended at Tue Aug 23 20:34:59 UTC 2016 in 1098 milliseconds
null
Fsck on path '/path/to/parent/dir/' FAILED
{code}
So I start at the top, fscking every subdirectory until I find one or more that
fails. Then I do the same thing with those directories (our top level
directories all have subdirectories with date directories in them, which then
contain the files) and once I find a directory with files in it, I run a
checksum of the files in that directory. When I do that, I don't get the name
of the file, rather I get:
checksum: java.lang.NullPointerException
but since the files are in order, I can figure it out by seeing which file was
before the NPE. Once I get to this point, I can see the following in the
namenode log when I try to checksum the corrupt file:
2016-08-23 20:24:59,627 WARN
org.apache.hadoop.hdfs.server.blockmanagement.BlockManager: Inconsistent number
of corrupt replicas for blk_1335893388_1100036319546 blockMap has 0 but corrupt
replicas map has 1
2016-08-23 20:24:59,627 WARN org.apache.hadoop.ipc.Server: IPC Server handler
23 on 8020, call
org.apache.hadoop.hdfs.protocol.ClientProtocol.getBlockLocations from
192.168.1.100:47785 Call#1 Retry#0
java.lang.NullPointerException
At which point I can delete the file, but it is a very tedious process.
Ideally, shouldn't fsck be able to emit the name of the file that is the source
of the problem - and (if -delete is specified) get rid of the file, instead of
exiting without saying why?
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