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From aaron morton <aa...@thelastpickle.com>
Subject Re: quick question on seed nodes configuration
Date Wed, 26 Jun 2013 08:45:11 GMT
>  I had seed nodes ip1,ip2,ip3 as the seeds but what I didn't realize was then that these
nodes had themselves as seeds.  I am assuming that should never be done, is that correct.

The only reason nodes listing them selves as seeds can be a pain is during bootstrap. Seeds
nodes will not stream data to themselves. 

> QUESTION: Would it be ok if I just configured every node to be the 3 ip's after it like
this instead as well
It's generally accepted to list the same 3 nodes from each DC on all nodes. 
 
> So, the most secure way is to write all your other nodes as seed, 
This may have a small impact on gossip. Gossip rounds go to a live node, a down node with
some probability and a seed node with some probability. 

                /* Gossip with the seed with some probability. */
                double probability = seeds.size() / (double)( liveEndpoints.size() + unreachableEndpoints.size()
);
                double randDbl = random.nextDouble();
                if ( randDbl <= probability )
                    sendGossip(prod, seeds);

If you have every node a seed it looks like you would always gossip to a seed. 

Cheers
 
-----------------
Aaron Morton
Freelance Cassandra Consultant
New Zealand

@aaronmorton
http://www.thelastpickle.com

On 25/06/2013, at 2:43 AM, julien Campan <julien.campan@gmail.com> wrote:

> Hi ,
> 
> The seeds are only used when a node appears in the cluster. At this moment it chooses
a seed (in the same dc) in order to have some information. 
> 
> So, the most secure way is to write all your other nodes as seed, but in fact you need
only one up.
> if you think that you will never have 3 node down at the same time , you can put only
three nodes.
> 
> 
> Julien Campan
> 
> 
> 2013/6/24 Hiller, Dean <Dean.Hiller@nrel.gov>
> For ease of use, we actually had a single cassandra.yaml deployed to every machine and
a script that swapped out the token and listen address.  I had seed nodes ip1,ip2,ip3 as the
seeds but what I didn't realize was then that these nodes had themselves as seeds.  I am assuming
that should never be done, is that correct.  I really should deploy ip1, ip2, ip3 on all nodes
and then for nodes 1, 2, and 3, I should do something like
> 
> ip1 will have ip2, ip3, ip4
> ip2 will have ip1, ip3, ip4
> Etc. etc.
> 
> QUESTION: Would it be ok if I just configured every node to be the 3 ip's after it like
this instead as well
> ip1 would have ip2, ip3, ip4
> ip2 would have ip3, ip4, ip5
> ip3 would have ip4, ip5, ip6
> ip4 would have ip5, ip6, ip1
> 
> Is this okay for seed node configuration?
> 
> Thanks,
> Dean
> 
> 


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