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From Daniel Templeton <dan...@cloudera.com>
Subject Re: Multiple namenodes
Date Fri, 22 Jul 2016 17:27:38 GMT
On 7/22/16 8:45 AM, Kun Ren wrote:
> (1).  How to create/start multiple namenodes?

Just pretend like you have two separate HDFS clusters and set them up 
that way.  (That is actually what you have.)

> (2). Once I have multiple Namenodes running, do you think what is the
> best/simple way to change the HDFS client code to let the clients send the
> requests to a random Namenode?

The client code is already built to try multiple NNs to handle HA. You 
can look there for inspiration.  If you want random, grab a random 
number and mod it by the number of NNs, then use that as an index into 
the list of NNs.

> (3). I need to support the communication between the Namenodes, my current
> plan is to create one more protocol that supports the communication between
> the Namenodes, something like the clientProtocol and
> ClientDataNodeProtocol. Do you think is it easy to do so? Or do you have
> other suggestions to support the communication between the Namenodes?

You will indeed need to define a new protocol.  Not the easiest thing in 
the world, but there are plenty of docs on protobuf.  Good luck!

Daniel

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