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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-10360.001.patch
Upload a proof of concept for the fix proposed in #1.
> DataNode may format directory and lose blocks if 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
>
>
> 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. 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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