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From Jay Booth <jaybo...@gmail.com>
Subject Re: HDFS Blockreport question
Date Thu, 01 Apr 2010 15:50:22 GMT
In DataNode:
public DatanodeProtocol namenode

It's not a reference to an actual namenode, it's a wrapper for a network
protocol created by that RPC.waitForProxy call -- so when it calls
namenode.blockReport, it's sending that information over RPC to the namenode
instance over the network

On Thu, Apr 1, 2010 at 5:50 AM, Alberich de megres <alberich2k5@gmail.com>wrote:

> Hi everyone!
> sailing throught the hdfs source code that comes with hadoop 0.20.2, i
> could not understand how hdfs sends blockreport to nameNode.
> As i can see, in
> src/hdfs/org/apache/hadoop/hdfs/server/datanode/DataNode.java we
> create this.namenode interface with RPC.waitForProxy call (wich i
> could not understand which class it instantiates, and how it works).
> After that, datanode generates block list report (blockListAsLongs)
> with data.getBlockReport, and call this.namenode.blockReport(..),
> inside namenode.blockReport it calls again namesystem.processReport.
> This leads to an update of block lists inside nameserver.
> But how it sends over the network this blockreport?
> Anyone can point me some light?
> thanks for all!
> (and sorry for the newbie question)
> Alberich

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