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Date: Sat, 2 Apr 2016 11:35:25 +0000 (UTC)
From: "Dimitrios Sarigiannis (JIRA)" <jira@apache.org>
To: hdfs-issues@hadoop.apache.org
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Subject: [jira] [Updated] (HDFS-10252) Is DataNode aware of the name of the
 file that it is going to store?
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     [ https://issues.apache.org/jira/browse/HDFS-10252?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Dimitrios Sarigiannis updated HDFS-10252:
-----------------------------------------
    Summary: Is DataNode aware of the name of the file that it is going to store?  (was: Is DataNode aware of name of the file that it is going to store?)

> Is DataNode aware of the name of the file that it is going to store?
> --------------------------------------------------------------------
>
>                 Key: HDFS-10252
>                 URL: https://issues.apache.org/jira/browse/HDFS-10252
>             Project: Hadoop HDFS
>          Issue Type: Test
>          Components: datanode, namenode
>            Reporter: Dimitrios Sarigiannis
>            Priority: Minor
>
> I am going through the HDFS Namenode and Datanode code and I am trying to see if the DataNode is aware of the names of the files that are stored in it (and other metadata as well).
> Assuming that we have the most simple case: 
> 1 NameNode
> 1 DataNode
> 1 single machine running HDFS with replication factor 1. 
> and considering the way HDFS works a use case could be: 
> A client requests to write a file from local to HDFS
> "hdfs dfs -put file /file"
> He first communicates with NameNode and gets where this file should be stored.
> Then, after receiving an answer, he requests to the DataNode to store that file.
> (At that point I am going to be a little more specific about the code)
> The DataNode has a DataXceiverServer class which runs and waits for requests. When a request comes, it starts a DataXceiver thread and try to serve that request. What I would like to know is, if at that specific point the DataNode knows the name of the file that it is going to store. I spent hours of debugging but I could not find it. Is it somewhere there, or only the NameNode knows the name of that file?


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