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https://issues.apache.org/jira/browse/HDFS-10360?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Wei-Chiu Chuang updated HDFS-10360:
-----------------------------------
Attachment: HDFS-10360.002.patch
Rev02: add log to record what files are being deleted during a DataNode
reformat operation. There's no need to add extra JMX reporting code, as long as
an IOException thrown adding the volume, it is added into JMX by the existing
code.
The test failures seems unrelated. I don't have these test failures in my tree.
> DataNode may format directory and lose blocks if current/VERSION is missing
> ---------------------------------------------------------------------------
>
> Key: HDFS-10360
> URL: https://issues.apache.org/jira/browse/HDFS-10360
> Project: Hadoop HDFS
> Issue Type: Bug
> Components: datanode
> Reporter: Wei-Chiu Chuang
> Assignee: Wei-Chiu Chuang
> Attachments: HDFS-10360.001.patch, HDFS-10360.002.patch
>
>
> Under certain circumstances, if the current/VERSION of a storage directory is
> missing, DataNode may format the storage directory even though _block files
> are not missing_.
> This is very easy to reproduce. Simply launch a HDFS cluster and create some
> files. Delete current/VERSION, and restart the data node.
> After the restart, the data node will format the directory and remove all
> existing block files:
> {noformat}
> 2016-05-03 12:57:15,387 INFO org.apache.hadoop.hdfs.server.common.Storage:
> Lock on /data/dfs/dn/in_use.lock acquired by nodename
> [email protected]
> 2016-05-03 12:57:15,389 INFO org.apache.hadoop.hdfs.server.common.Storage:
> Storage directory /data/dfs/dn is not formatted for
> BP-787466439-172.26.24.43-1462305406642
> 2016-05-03 12:57:15,389 INFO org.apache.hadoop.hdfs.server.common.Storage:
> Formatting ...
> 2016-05-03 12:57:15,464 INFO org.apache.hadoop.hdfs.server.common.Storage:
> Analyzing storage directories for bpid BP-787466439-172.26.24.43-1462305406642
> 2016-05-03 12:57:15,464 INFO org.apache.hadoop.hdfs.server.common.Storage:
> Locking is disabled for
> /data/dfs/dn/current/BP-787466439-172.26.24.43-1462305406642
> 2016-05-03 12:57:15,465 INFO org.apache.hadoop.hdfs.server.common.Storage:
> Block pool storage directory
> /data/dfs/dn/current/BP-787466439-172.26.24.43-1462305406642 is not formatted
> for BP-787466439-172
> .26.24.43-1462305406642
> 2016-05-03 12:57:15,465 INFO org.apache.hadoop.hdfs.server.common.Storage:
> Formatting ...
> 2016-05-03 12:57:15,465 INFO org.apache.hadoop.hdfs.server.common.Storage:
> Formatting block pool BP-787466439-172.26.24.43-1462305406642 directory
> /data/dfs/dn/current/BP-787466439-172.26.24.43-1462305406642/current
> {noformat}
> The bug is: DataNode assumes that if none of {{current/VERSION}},
> {{previous/}}, {{previous.tmp/}}, {{removed.tmp/}}, {{finalized.tmp/}} and
> {{lastcheckpoint.tmp/}} exists, the storage directory contains nothing
> important to HDFS and decides to format it.
> https://github.com/apache/hadoop/blob/trunk/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/common/Storage.java#L526-L545
> However, block files may still exist, and in my opinion, we should do
> everything possible to retain the block files.
> I have two suggestions:
> # check if {{current/}} directory is empty. If not, throw an
> InconsistentFSStateException in {{Storage#analyzeStorage}} instead of
> asumming its not formatted. Or,
> # In {{Storage#clearDirectory}}, before it formats the storage directory,
> rename or move {{current/}} directory. Also, log whatever is being
> renamed/moved.
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