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Date: Wed, 20 Feb 2008 11:35:43 -0800 (PST)
From: "Konstantin Shvachko (JIRA)" <jira@apache.org>
To: core-dev@hadoop.apache.org
Subject: [jira] Commented: (HADOOP-2815) support for DeleteOnExit
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    [ https://issues.apache.org/jira/browse/HADOOP-2815?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12570806#action_12570806 ] 

Konstantin Shvachko commented on HADOOP-2815:
---------------------------------------------

Another simple solution to this would be if you just keep temporary files open and never close them.
With the new semantics files under construction are readable for all clients.
When the client that created (but did not close) a file dies the lease should expire in due time, and hdfs will automatically remove it.
I am only worried about if  too many open files will slow down the name-node.
How many temp files do you need and for how long they should remain open?

> support for DeleteOnExit
> ------------------------
>
>                 Key: HADOOP-2815
>                 URL: https://issues.apache.org/jira/browse/HADOOP-2815
>             Project: Hadoop Core
>          Issue Type: New Feature
>          Components: dfs
>            Reporter: Olga Natkovich
>
> 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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