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From "dhruba borthakur (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HDFS-1779) After NameNode restart , Clients can not read partial files even after client invokes Sync.
Date Sat, 26 Mar 2011 05:19:05 GMT

    [ https://issues.apache.org/jira/browse/HDFS-1779?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13011567#comment-13011567
] 

dhruba borthakur commented on HDFS-1779:
----------------------------------------

Wait a minute, can you pl provide some more clarification? If you restart only the NN and
not the DN, then the DN still has a reference to the blocks in the bbw directory. When the
client closes the file (assuming that the client survived the NN restart), those blocks will
send a blockReceived to the NN. If the client died, then the NN will start lease-recovery
at some future point in time and that should make these datanodes send blockReceived messages
to the NN. This sequence of events should make the blocks reappear in the NN. Are you seeing
something different?

> After NameNode restart , Clients can not read partial files even after client invokes
Sync.
> -------------------------------------------------------------------------------------------
>
>                 Key: HDFS-1779
>                 URL: https://issues.apache.org/jira/browse/HDFS-1779
>             Project: Hadoop HDFS
>          Issue Type: Bug
>          Components: data-node, name-node
>    Affects Versions: 0.20-append
>         Environment: Linux
>            Reporter: Uma Maheswara Rao G
>
> In Append HDFS-200 issue,
> If file has 10 blocks and after writing 5 blocks if client invokes sync method then NN
will persist the blocks information in edits. 
> After this if we restart the NN, All the DataNodes will reregister with NN. But DataNodes
are not sending the blocks being written information to NN. DNs are sending the blocksBeingWritten
information in DN startup. So, here NameNode can not find that the 5 persisted blocks belongs
to which datanodes. This information can build based on block reports from DN. Otherwise we
will loose this 5 blocks information even NN persisted that block information in edits. 

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