[
https://issues.apache.org/jira/browse/HDFS-1690?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13014395#comment-13014395
]
Konstantin Shvachko commented on HDFS-1690:
-------------------------------------------
The purpose for the lock file "in_use.lock" is to hold a lock on that file
while the NameNode is running. This is in order to prevent from accidentally
starting another NN in the same directory, which can mess up the fsimage and
the edits.
When the NameNode shuts down abruptly, which it always does, as there is no
other way to stop the NameNode but to kill it, the lock on the lock file will
be released, and the format will be able to delete the file.
Locking may be platform dependent, but is known to work for most traditional
file systems.
> Name Node should not process format command while it is running.
> ----------------------------------------------------------------
>
> Key: HDFS-1690
> URL: https://issues.apache.org/jira/browse/HDFS-1690
> Project: Hadoop HDFS
> Issue Type: Bug
> Components: name-node
> Affects Versions: 0.20.1, 0.20.2, 0.21.0
> Reporter: Uma Maheswara Rao G
> Assignee: Uma Maheswara Rao G
> Attachments: HDFS-1690.patch
>
>
> Currently NameNode allows format command while it running. In this case the
> command is executed partially (Lock file is deleted) and an exception thrown.
> Because of this Name Node should be formatted after restart. This sort of
> cases can happen accidentally. To prevent such cases Name Node should not
> execute the format command partially while it is running. It can stright away
> throw exception/log saying, Name Node is running.
--
This message is automatically generated by JIRA.
For more information on JIRA, see: http://www.atlassian.com/software/jira
