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From "Brandon Li (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HDFS-5924) Utilize OOB upgrade message processing for writes
Date Thu, 20 Feb 2014 20:44:20 GMT

    [ https://issues.apache.org/jira/browse/HDFS-5924?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13907471#comment-13907471
] 

Brandon Li commented on HDFS-5924:
----------------------------------

{quote}This feature does not guarantee all client writes to continue across restart. {quote}
Would it cause data loss? especially when the only one or more than one datanode in the pipeline
is shutting down for upgrade.

> Utilize OOB upgrade message processing for writes
> -------------------------------------------------
>
>                 Key: HDFS-5924
>                 URL: https://issues.apache.org/jira/browse/HDFS-5924
>             Project: Hadoop HDFS
>          Issue Type: Sub-task
>          Components: datanode, ha, hdfs-client, namenode
>            Reporter: Kihwal Lee
>            Assignee: Kihwal Lee
>         Attachments: HDFS-5924_RBW_RECOVERY.patch, HDFS-5924_RBW_RECOVERY.patch
>
>
> After HDFS-5585 and HDFS-5583, clients and datanodes can coordinate shutdown-restart
in order to minimize failures or locality loss.
> In this jira, HDFS client is made aware of the restart OOB ack and perform special write
pipeline recovery. Datanode is also modified to load marked RBW replicas as RBW instead of
RWR as long as the restart did not take long. 
> For clients, it considers doing this kind of recovery only when there is only one node
left in the pipeline or the restarting node is a local datanode.  For both clients and datanodes,
the timeout or expiration is configurable, meaning this feature can be turned off by setting
timeout variables to 0.



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