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From "Uma Maheswara Rao G (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HDFS-1690) Name Node should not process format command while it is running.
Date Thu, 30 Jun 2011 13:31:28 GMT

    [ https://issues.apache.org/jira/browse/HDFS-1690?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13057816#comment-13057816
] 

Uma Maheswara Rao G commented on HDFS-1690:
-------------------------------------------

Hi Konstantin,
Thankyou for the comments

{quote}
  I think we can just skip checking the presence of in_use.lock during formatting and go directly
to setting the lock on that file? The effect will be the same. If file does not exist, it
will create and lock it.
{quote}
  No. First itself i will check the in_use.lock file presence. After that only i am going
for other conditions.
  
Above mentioned proposal is:
 1) if in_use.lock not present then we can allow for formatting.

 2) If in_use.lock present, then we need to check for lock. If it is allowing to   take lock
then we can allow formatting.If it is not allowing to take lock then we should not allow for
format.


{quote}
So I'd propose to modify StorageDirectory.clearDirectory() to first delete file STORAGE_FILE_LOCK=in_use.lock
then the rest of it. I see now it's a bug.
{quote}
    But here the problem could be that , As i know in Linux, always i can delete the files,
no matter other process is using it or not.


One more idea i got,
 i.e, why con't we restrict besed on PID in script file itself ?. 
  It is like, how hadoop start script will restrict to start the process when it is already
running.




> 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.

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