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From "Olga Natkovich (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HADOOP-2815) Allowing processes to cleanup dfs on shutdown
Date Mon, 03 Mar 2008 21:20:50 GMT

    [ https://issues.apache.org/jira/browse/HADOOP-2815?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12574740#action_12574740
] 

Olga Natkovich commented on HADOOP-2815:
----------------------------------------

Pig needs this on the directory not file level. The use case is chaining of map-reduce jobs.
The data between 2 M-R jobs is created by the first M-R job and consumed by the next so we
don't want them to be deleted when the first M-R job is done. 

The way pig does it now is

- Client create temp dir
- First M-R job writes there
- Second job reads from there
- Client cleans up at the end.

We need to be able for the client to mark the directory as "delete on exit" and to be cleaned
once the client is done.

> Allowing processes to cleanup dfs on shutdown
> ---------------------------------------------
>
>                 Key: HADOOP-2815
>                 URL: https://issues.apache.org/jira/browse/HADOOP-2815
>             Project: Hadoop Core
>          Issue Type: New Feature
>          Components: dfs
>            Reporter: Olga Natkovich
>            Assignee: dhruba borthakur
>
> Pig creates temp files that it wants to be removed at the end of the processing. The
code that removes the temp file is in the shutdown hook so that they get removed both under
normal shutdown as well as when process gets killed.
> The problem that we are seeing is that by the time the code is called the DFS might already
be closed and the delete fails leaving temp files behind. Since we have no control over the
shutdown order, we have no way to make sure that the files get removed.
> One way to solve this issue is to be able to mark the files as temp files so that hadoop
can remove them during its shutdown.
> The stack trace I am seeing is
> at org.apache.hadoop.dfs.DFSClient.checkOpen(DFSClient.java:158)
>         at org.apache.hadoop.dfs.DFSClient.delete(DFSClient.java:417)
>         at org.apache.hadoop.dfs.DistributedFileSystem.delete(DistributedFileSystem.java:144)
>         at org.apache.pig.backend.hadoop.datastorage.HPath.delete(HPath.java:96)
>         at org.apache.pig.impl.io.FileLocalizer$1.run(FileLocalizer.java:275)

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