Mailing-List: contact hdfs-issues-help@hadoop.apache.org; run by ezmlm
Precedence: bulk
Reply-To: hdfs-issues@hadoop.apache.org
Message-ID: <1282089959.90071267769847347.JavaMail.jira@brutus.apache.org>
Date: Fri, 5 Mar 2010 06:17:27 +0000 (UTC)
From: "Hairong Kuang (JIRA)" <jira@apache.org>
To: hdfs-issues@hadoop.apache.org
Subject: [jira] Commented: (HDFS-826) Allow a mechanism for an application
 to detect that datanode(s)  have died in the write pipeline
In-Reply-To: <286045347.1260478518783.JavaMail.jira@brutus>
MIME-Version: 1.0
Content-Type: text/plain; charset=utf-8
Content-Transfer-Encoding: 7bit


    [ https://issues.apache.org/jira/browse/HDFS-826?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12841717#action_12841717 ] 

Hairong Kuang commented on HDFS-826:
------------------------------------

I do not think that making the user aware of whether the replicas are created or not is a bad idea. Why hiding this is better? Less code change but providing the user more information seems to me is very good. But I do not mean that you have to do it this way. It is just a suggestion. :-) 

> Allow a mechanism for an application to detect that datanode(s)  have died in the write pipeline
> ------------------------------------------------------------------------------------------------
>
>                 Key: HDFS-826
>                 URL: https://issues.apache.org/jira/browse/HDFS-826
>             Project: Hadoop HDFS
>          Issue Type: Improvement
>          Components: hdfs client
>            Reporter: dhruba borthakur
>            Assignee: dhruba borthakur
>         Attachments: Replicable4.txt, ReplicableHdfs.txt, ReplicableHdfs2.txt, ReplicableHdfs3.txt
>
>
> HDFS does not replicate the last block of the file that is being currently written to by an application. Every datanode death in the write pipeline decreases the reliability of the last block of the currently-being-written block. This situation can be improved if the application can be notified of a datanode death in the write pipeline. Then, the application can decide what is the right course of action to be taken on this event.
> In our use-case, the application can close the file on the first datanode death, and start writing to a newly created file. This ensures that the reliability guarantee of a block is close to 3 at all time.
> One idea is to make DFSOutoutStream. write() throw an exception if the number of datanodes in the write pipeline fall below minimum.replication.factor that is set on the client (this is backward compatible).

-- 
This message is automatically generated by JIRA.
-
You can reply to this email to add a comment to the issue online.