[ https://issues.apache.org/jira/browse/HDFS-826?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12839875#action_12839875 ]
Konstantin Shvachko commented on HDFS-826: ------------------------------------------ What is the point of introducing new {{Replicable}} interface if it is not used anywhere? The new method {{getNumCurrentReplicas()}} in {{FSOutputSummer}} would work fine. > 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: 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.