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https://issues.apache.org/jira/browse/HADOOP-6761?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Dmytro Molkov updated HADOOP-6761:
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    Attachment: HADOOP-6761.3.patch

To have backward compatible behaviour the default value of the emptier interval 
should be 0, then the trash value interval is used for checkpointing.

> Improve Trash Emptier
> ---------------------
>
>                 Key: HADOOP-6761
>                 URL: https://issues.apache.org/jira/browse/HADOOP-6761
>             Project: Hadoop Common
>          Issue Type: Improvement
>            Reporter: Dmytro Molkov
>            Assignee: Dmytro Molkov
>         Attachments: HADOOP-6761.2.patch, HADOOP-6761.3.patch, 
> HADOOP-6761.patch
>
>
> There are two inefficiencies in the Trash functionality right now that have 
> caused some problems for us.
> First if you configured your trash interval to be one day (24 hours) that 
> means that you store 2 days worth of data eventually. The Current and the 
> previous timestamp that will not be deleted until the end of the interval.
> And another problem is accumulating a lot of data in Trash before the Emptier 
> wakes up. If there are a couple of million files trashed and the Emptier does 
> deletion on HDFS the NameNode will freeze until everything is removed. (this 
> particular problem hopefully will be addressed with HDFS-1143).
> My proposal is to have two configuration intervals. One for deleting the 
> trashed data and another for checkpointing. This way for example for 
> intervals of one day and one hour we will only store 25 hours of data instead 
> of 48 right now and the deletions will be happening in smaller chunks every 
> hour of the day instead of a huge deletion at the end of the day now.

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