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From Marcus Bointon <mar...@synchromedia.co.uk>
Subject Re: EC2 node adding trouble
Date Wed, 25 May 2011 06:50:07 GMT
On 24 May 2011, at 23:58, Sameer Farooqui wrote:

> Even with AutoBootstrap it is recommended that you always specify the InitialToken on
the new node because the picking of an initial token will almost certainly result in an unbalanced
ring.
> 
> Right now, I'm afraid that if you simply copied the YAML file from one of the two nodes
to the 3rd node, then the 3rd node has an incorrect initial_token setting (it may be conflicting
with node 1 or 2's range). 
> 
> Some info about how to choose tokens:
> http://wiki.apache.org/cassandra/Operations#Token_selection
> http://journal.paul.querna.org/articles/2010/09/24/cassandra-token-selection/
> 
> So, once you know what token each of the 3 nodes should have, shut down the first two
nodes, change their tokens and add the correct token to the 3rd node (in the YAML file).

At the moment I'm not bothered about balance - just having it work at all would be good! initial_token
is currently blank (i.e. self-defining according to the docs) on all nodes - I can see why
that might cause balance issues, but I don't see that it would prevent it working as there
should not be a token clash. If there was a token clash, wouldn't it throw an error saying
so?

That second article, while wonderfully practical and informative, suggests that cassandra
is really not suited to rapid scaling up or down - i.e. adding or removing nodes is neither
quick nor painless, e.g. scaling from 5 to 20 nodes and back is something that might happen
over weeks rather than minutes. Maybe cassandra just isn't the right tool for the job in this
case?

Marcus
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