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From Igor <i...@4friends.od.ua>
Subject Re: How to add new DC to cluster when GossipingPropertyFileSnitch is used
Date Fri, 17 May 2013 08:42:14 GMT
On 05/17/2013 11:19 AM, Sergey Naumov wrote:
> But I've read in some sources (for example 
> http://www.datastax.com/docs/1.0/initialize/cluster_init_multi_dc) 
> that seed list MUST include at least one seed from each DC and seed 
> lists should be the same for each node.
>
> Or it is fine if nodes from new DC have all seeds specified and nodes 
> from old DCs have all seeds specified except seeds from new DC? In 
> such interpretation rules have to be a bit modified:

I never have problems with adding new nodes and new DC having single 
seed per cluster in one old DC.

> 1. Nodes from the same DC should have identical seeds lists.
> 2. At least at one DC nodes MUST have in its seed lists seeds from all 
> other DCs.
>
>
> 2013/5/17 Igor <igor@4friends.od.ua <mailto:igor@4friends.od.ua>>
>
>     I see no reason to restart all nodes. You can continue to use seed
>     from first DC - seed used for loading ring
>     configuration(locations, token ranges, etc), not data.
>
>     On 05/17/2013 10:34 AM, Sergey Naumov wrote:
>>     If I understand you correctly, GossipingPropertyFileSnitch is
>>     useful for manipulations with nodes within a single DC, but to
>>     add a new DC without having to restart every node in all DCs
>>     (because seeds are specified in cassandra.yaml and I need to
>>     restart a node after addition of a new seed from newly created
>>     DC), I anyway have to use cassandra-topology.properties and edit
>>     it on every node of a cluster.
>>
>>     By the way, it it necessary to specify seeds if I use
>>     PropertyFileSnitch and there is info in
>>     cassandra-topology.properties about all nodes of a cluster?
>>
>
>     Yes, it is. Cassandra need seed(s), because topology properties
>     have no info about token ranges.
>
>
>>
>>     2013/5/17 aaron morton <aaron@thelastpickle.com
>>     <mailto:aaron@thelastpickle.com>>
>>
>>         You should configure the seeds as recommended regardless of
>>         the snitch used.
>>
>>         You need to update the yaml file to start using the
>>         GossipingPropertyFileSnitch but after that it reads the
>>         cassandra-rackdc.properties file to get information about the
>>         node. It reads uses the information in gossip to get
>>         information about the other nodes in the cluster.
>>
>>         If there is no info in gossip about a remote node, because
>>         say it has not been upgraded, it will fall back to using
>>         cassandra-topology.properties.
>>
>>         Hope that helps.
>>
>>         -----------------
>>         Aaron Morton
>>         Freelance Cassandra Consultant
>>         New Zealand
>>
>>         @aaronmorton
>>         http://www.thelastpickle.com
>>
>>         On 15/05/2013, at 8:10 PM, Sergey Naumov <sknaumov@gmail.com
>>         <mailto:sknaumov@gmail.com>> wrote:
>>
>>         > As far as I understand, GossipingPropertyFileSnitch
>>         supposed to provide more flexibility in nodes
>>         addition/removal. But what about addition of a DC? In
>>         datastax documentation
>>         (http://www.datastax.com/docs/1.2/operations/add_replace_nodes#add-dc)
>>         it is said that cassandra-topology.properties could be
>>         updated without restart for PropertyFileSnitch. But here
>>         (http://www.datastax.com/docs/1.0/initialize/cluster_init_multi_dc)
>>         it it said, that "you MUST include at least one node from
>>         EACH data center. It is a best practice to have at more than
>>         one seed node per data center and the seed list should be the
>>         same for each node". At the first glance it seems that
>>         PropertyFileSnitch will get necessary info from
>>         cassandra-topology.properties, but for
>>         GossipingPropertyFileSnitch modification of cassandra.yaml
>>         and restart of all nodes in all DCs will be required. Could
>>         somebody clarify this topic?
>>         >
>>         > Thanks in advance,
>>         > Sergey Naumov.
>>
>>
>
>


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