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https://issues.apache.org/jira/browse/HADOOP-5027?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12665346#action_12665346
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dhruba borthakur commented on HADOOP-5027:
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When a client is creating a block for the first time, the block is not being
replicated by the NN. Only when the client is done writing to that block and
the block is finalized does the NN start to replicate the block (if needed).
The current design is to apply the above design to pre-existing block that is
being opened for "append". The NN will not replicate this block until the
appending-client is completely done with that block.
I agree with Rob that the availability guarantees of a block being re-opened
for write is not the same as a block that nobody is writing to. But "append" is
a new feature and HADOOP-1700 states that this guarantee is acceptable. Rob's
request is valid, but we can address that as an improvement over the current
design and attack it in a seperate JIRA. Does that sound reasonable?
This patch is imperative to make "appends" work as designed for 0.19.
> Block report processing should compare gneration stamp
> ------------------------------------------------------
>
> Key: HADOOP-5027
> URL: https://issues.apache.org/jira/browse/HADOOP-5027
> Project: Hadoop Core
> Issue Type: Bug
> Components: dfs
> Reporter: Tsz Wo (Nicholas), SZE
> Fix For: 0.19.1
>
> Attachments: 5027_20090114.patch
>
>
> If a reported block has a different generation stamp then the one stored in
> the NameNode, the reported block will be considered as invalid. This is
> incorrect since blocks with larger generation stamp are valid.
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