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From "Allen Wittenauer (JIRA)" <j...@apache.org>
Subject [jira] [Resolved] (HDFS-80) Rename of a directory with many opened files blocks name-node for a long time. changeLease() to blame.
Date Fri, 18 Jul 2014 05:29:05 GMT

     [ https://issues.apache.org/jira/browse/HDFS-80?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Allen Wittenauer resolved HDFS-80.
----------------------------------

    Resolution: Incomplete

Closing this as stale.

> Rename of a directory with many opened files blocks name-node for a long time. changeLease()
to blame.
> ------------------------------------------------------------------------------------------------------
>
>                 Key: HDFS-80
>                 URL: https://issues.apache.org/jira/browse/HDFS-80
>             Project: Hadoop HDFS
>          Issue Type: Bug
>            Reporter: Konstantin Shvachko
>
> I am creating a directory containing 200,000 files, and then renaming it.
> The rename operation is twice as long as the the total time for creating all those files.
> The worst thing is that the rename blocks the name-node for minutes. I tried it with
a bigger directory containing 1 mln files - it blocks for 30 minutes.
> The rename itself is fast, its the changeLease() called after renaming that takes all
the time.
> As I can see from the code changeLease() gets tailMap() of the directory that it renames
and scans the whole tail.
> If the number of open files is large as in my case this takes forever because the tailMap
includes all files in the subtree.
> Simple way to reproduce it is to run
> {code}
> NNThroughputBenchmark -op open -files N
> {code}
> with a large N. This will first create N files in directory "/NNThroughputBenchmark/create"
and then rename it to "/NNThroughputBenchmark/open".



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