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From "Uma Maheswara Rao G (Commented) (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HDFS-3119) Overreplicated block is not deleted even after the replication factor is reduced after sync follwed by closing that file
Date Wed, 21 Mar 2012 12:25:39 GMT

    [ https://issues.apache.org/jira/browse/HDFS-3119?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13234309#comment-13234309
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Uma Maheswara Rao G commented on HDFS-3119:
-------------------------------------------

Replication is not per block. This is per file configuration.
Also we will persist the replication factor in edits. So, looks this setTeplication will get
applied properly only for completed blocks.
But for the in-complete blocks, there won't be any blocks updated in blocksMap. So, nonExcess
nodes would be 0. So, it can't remove any nodes at the moment.

I am not sure whether we are checking for the replication count while completing the block.


If we really need this to work, 
1) one way is to check the replication consistency while completing the block as new replication
already persisted.

(Or)

2)  completely we can restrict setReplication call for non-closed files?

 blockreport also may not detect this case.

Let me recheck again if I am missing something.
                
> Overreplicated block is not deleted even after the replication factor is reduced after
sync follwed by closing that file
> ------------------------------------------------------------------------------------------------------------------------
>
>                 Key: HDFS-3119
>                 URL: https://issues.apache.org/jira/browse/HDFS-3119
>             Project: Hadoop HDFS
>          Issue Type: Bug
>          Components: name-node
>    Affects Versions: 0.24.0
>            Reporter: J.Andreina
>            Priority: Minor
>             Fix For: 0.24.0, 0.23.2
>
>
> cluster setup:
> --------------
> 1NN,2 DN,replication factor 2,block report interval 3sec ,block size-256MB
> step1: write a file "filewrite.txt" of size 90bytes with sync(not closed) 
> step2: change the replication factor to 1  using the command: "./hdfs dfs -setrep 1 /filewrite.txt"
> step3: close the file
> * At the NN side the file "Decreasing replication from 2 to 1 for /filewrite.txt" , logs
has occured but the overreplicated blocks are not deleted even after the block report is sent
from DN
> * while listing the file in the console using "./hdfs dfs -ls " the replication factor
for that file is mentioned as 1
> * In fsck report for that files displays that the file is replicated to 2 datanodes

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