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From Shinichi Yamashita <shin1...@gmail.com>
Subject Re: How to change topology
Date Tue, 09 Oct 2012 15:51:04 GMT
Hi Steve,

Thank you for your reply.

> no, it's the Namenode and JobTracker that needs to be restarted;
> they are the bits that care where the boxes are.

I confirmed it in my cluster, and I understood it as follows.
First, the resolved node information is recorded in ConcurrentHashMap.
Next same node toplogy decision, HashMap data is given priority to over a
script.
The HashMap data become invalid by restart of NameNode and JobTracker.

Regards,
Shinichi

2012/10/9 Steve Loughran <stevel@hortonworks.com>

>
>
> On 8 October 2012 14:23, Shinichi Yamashita <shin1.ym@gmail.com> wrote:
>
>> Hi,
>>
>> I know that DataNode and TaskTracker must restart to change topology.
>>
>
> no, it's the Namenode and JobTracker that needs to be restarted; they are
> the bits that care where the boxes are.
>
>
>> Is there the method to execute the topology change without restart of
>> DataNode and TaskTracker?
>> In other words, can I change the topology by a command?
>>
>
> No -the map gets cached, and when the services start up they do quick
> check to see if the topology is flat or spread across switches -and use
> that flag to make various placement decisions.
>
> steve
>
>
>

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