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From "Kihwal Lee (JIRA)" <j...@apache.org>
Subject [jira] [Comment Edited] (HDFS-5583) Make DN send an OOB Ack on shutdown before restaring
Date Wed, 19 Feb 2014 21:26:31 GMT

    [ https://issues.apache.org/jira/browse/HDFS-5583?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13906104#comment-13906104
] 

Kihwal Lee edited comment on HDFS-5583 at 2/19/14 9:26 PM:
-----------------------------------------------------------

Thanks for the review, Brandon.

- The admin wants to know whether the command was received by the datanode: This is determined
by the return code of the command. As with other commands, when the return code is not 0,
the state is non-deterministic and only then the command may be reissued. I do not believe
that this is a common case.  Moreover, the shutdown normally takes less than two seconds and
probably the reissuing shutdown manually takes more than that. In my opinion, adding support
for reporting progress won't have much value. If you still feel that it needs to be changed,
I will change it. Please let me know what you think.

- I am planning on adding at least one more OOB ack type in near future for write draining,
which will be useful for decommissioining. The reserved enums make certain checks more efficient.

I will address the rest of the comments when you finish the review.


was (Author: kihwal):
Thanks for the review, Brandon.

- The admin wants to know whether the command was received: This is determined by the return
code of the command. As with other commands, when the return code is not 0, the state is non-deterministic
and only then the command may be reissued. I do not believe that this is a common case.  Moreover,
the shutdown normally take less than two seconds and probably the reissuing shutdown manually
take more than that. In my opinion, adding support for reporting progress won't have much
value. If you still feel that it needs to be changed, I will change it. Please let me know
what you think.

- I am planning on adding at least one more OOB ack type in near future for write draining,
which will be useful for decommissioining. The reserved enums make certain checks more efficient.

I will address the rest of the comments when you finish the review.

> Make DN send an OOB Ack on shutdown before restaring
> ----------------------------------------------------
>
>                 Key: HDFS-5583
>                 URL: https://issues.apache.org/jira/browse/HDFS-5583
>             Project: Hadoop HDFS
>          Issue Type: Sub-task
>            Reporter: Kihwal Lee
>            Assignee: Kihwal Lee
>         Attachments: HDFS-5583.patch, HDFS-5583.patch, HDFS-5583.patch
>
>
> Add an ability for data nodes to send an OOB response in order to indicate an upcoming
upgrade-restart. Client should ignore the pipeline error from the node for a configured amount
of time and try reconstruct the pipeline without excluding the restarted node.  If the node
does not come back in time, regular pipeline recovery should happen.
> This feature is useful for the applications with a need to keep blocks local. If the
upgrade-restart is fast, the wait is preferable to losing locality.  It could also be used
in general instead of the draining-writer strategy.



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