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https://issues.apache.org/jira/browse/HDFS-13826?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16580755#comment-16580755
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Todd Lipcon commented on HDFS-13826:
------------------------------------

Thanks for pointing me at Dynamometer. That's quite interesting as it's 
high-fidelity and simulates block reports, NN memory usage more accurately, 
etc. I'll take a look at whether we can use that for our use case. If not, then 
yea, the scope you described is just about it -- just a check if this setting 
is configured and calling out to some other function to generate fake results 
if so. Only a couple line hook into existing code and maybe 100 new lines 
elsewhere to do the generation.

> Add a hidden configuration for NameNode to generate fake block locations
> ------------------------------------------------------------------------
>
>                 Key: HDFS-13826
>                 URL: https://issues.apache.org/jira/browse/HDFS-13826
>             Project: Hadoop HDFS
>          Issue Type: Improvement
>          Components: namenode
>            Reporter: Todd Lipcon
>            Assignee: Todd Lipcon
>            Priority: Minor
>
> In doing testing and benchmarking of the NameNode and dependent systems, it's 
> often useful to be able to use an fsimage provided by some production system 
> in a controlled environment without actually having access to any of the 
> data. For example, while doing some recent work on Apache Impala I was trying 
> to optimize the transmission and storage of block locations and tokens and 
> measure the results based on metadata from a production user. In order to 
> achieve this, it would be useful for the NN to expose a developer-only 
> (undocumented) configuration to generate fake block locations and return them 
> to callers. The "fake" locations should be randomly distributed across a 
> fixed set of fake datanodes.



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