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From aaron morton <aa...@thelastpickle.com>
Subject Re: about decommissioned node that returns
Date Tue, 20 Dec 2011 19:31:29 GMT
> - What happens in Cassandra with a failed node that has been
> decommissioned if it returns to the cluster with old data and its old
> token?
If it starts normally it *may* take ownership of the token away from the previous node. The
Gossip Generation is compared and the server with the higher value is the one that keeps the
token. Normally the generation is seeded with the current time when the server first starts
and is then increased everytime something significant happens, like a server restart. 

So if you restarted the old node with the same system CFs, maybe the old node would get ownership
of the token. If you restart it after removing the system CFs it will most likely take ownership.

> - Will it actualize the data using ReadRepair or the bootstrapping process?

Bootstrap only runs the first time the server starts, technically when data is not present
in the system CF's. So if you restart without changing the system CF's use a repair.

> - And what if it has changed its IP?
Does not matter. Tokens are the thing. 

Best thing would be to bring the node back into the the ring as a new clean node. 

Hope that helps. 

-----------------
Aaron Morton
Freelance Developer
@aaronmorton
http://www.thelastpickle.com

On 21/12/2011, at 5:24 AM, Carlos Pérez Miguel wrote:

> Hello,
> 
> I have several questions about decommissioned nodes that I would like
> to clarify:
> 
> - What happens in Cassandra with a failed node that has been
> decommissioned if it returns to the cluster with old data and its old
> token?
> - Will it actualize the data using ReadRepair or the bootstrapping process?
> - Or it will be ignored or reconnected with another token?
> - And what if it has changed its IP?
> 
> Thank you
> 
> Carlos Pérez Miguel


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