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From "Hairong Kuang (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HDFS-1520) HDFS 20 append: Lightweight NameNode operation to trigger lease recovery
Date Mon, 29 Nov 2010 23:49:14 GMT

    [ https://issues.apache.org/jira/browse/HDFS-1520?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12965009#action_12965009
] 

Hairong Kuang commented on HDFS-1520:
-------------------------------------

I do not think this needs to go into trunk for now. With trunk, HBase should be able to read
the unclosed file and get all hflushed data. So there is no need to close HLog before splitting.

> HDFS 20 append: Lightweight NameNode operation to trigger lease recovery
> ------------------------------------------------------------------------
>
>                 Key: HDFS-1520
>                 URL: https://issues.apache.org/jira/browse/HDFS-1520
>             Project: Hadoop HDFS
>          Issue Type: New Feature
>    Affects Versions: 0.20-append
>            Reporter: Hairong Kuang
>            Assignee: Hairong Kuang
>             Fix For: 0.20-append
>
>
> Currently HBase uses append to trigger the close of HLog during Hlog split. Append is
a very expensive operation, which involves not only NameNode operations but creating a writing
pipeline. If one of datanodes on the pipeline has a problem, this recovery may takes minutes.
I'd like implement a lightweight NameNode operation to trigger lease recovery and make HBase
to use this instead.

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