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From Jon Haddad <jonathan.had...@gmail.com>
Subject Re: Service discovery in the Cassandra cluster
Date Mon, 01 May 2017 23:45:50 GMT
Why do you have to figure out what’s up w/ them by accident?  You’ve gotten all the information
you need.  Seeds are used to get the initial state of the cluster and as an optimization to
spread gossip faster.  That’s it.  



> On May 1, 2017, at 4:37 PM, Roman Naumenko <roman@sproutling.com> wrote:
> 
> Well, I guess I have to figure out what’s up with IPs/hostnames by experiment.
> Information about service discovery is practically absent.
> Not to mention all important details about fqdns/hostnames, automatic replacing seed
nodes or what not. 
> 
> —
> Roman
> 
>> On May 1, 2017, at 4:14 PM, Jon Haddad <jonathan.haddad@gmail.com <mailto:jonathan.haddad@gmail.com>>
wrote:
>> 
>> The in-tree docs do not mention this anywhere, and even have some of the answers
you’re asking:
>> 
>> https://cassandra.apache.org/doc/latest/faq/index.html?highlight=seed#what-are-seeds
<https://cassandra.apache.org/doc/latest/faq/index.html?highlight=seed#what-are-seeds>
>> 
>> The DataStax docs are maintained outside of the project, you’ll have to ask them
why they’re wrong or misleading.
>> 
>> Jon
>> 
>>> On May 1, 2017, at 4:10 PM, Roman Naumenko <roman@sproutling.com <mailto:roman@sproutling.com>>
wrote:
>>> 
>>> The docs mention IP addresses everywhere.
>>> 
>>> http://docs.datastax.com/en/archived/cassandra/2.0/cassandra/operations/ops_replace_seed_node.html
<http://docs.datastax.com/en/archived/cassandra/2.0/cassandra/operations/ops_replace_seed_node.html>
>>> Promote an existing node to a seed node by adding its IP address to -seeds list
and remove (demote) the IP address of the dead seed node from the cassandra.yaml file for
each node in the cluster.
>>> 
>>> http://docs.datastax.com/en/archived/cassandra/2.0/cassandra/operations/ops_replace_node_t.html
<http://docs.datastax.com/en/archived/cassandra/2.0/cassandra/operations/ops_replace_node_t.html>
>>> Note the Address of the dead node; it is used in step 5.
>>> 
>>> http://docs.datastax.com/en/cassandra/2.1/cassandra/initialize/initializeSingleDS.html
<http://docs.datastax.com/en/cassandra/2.1/cassandra/initialize/initializeSingleDS.html>
>>>> Properties to set:
>>>> num_tokens: recommended value: 256
>>>> -seeds: internal IP address of each seed node
>>> 
>>> I saw also hostnames mentioned few times, but it just makes it even more confusing.
>>> 
>>> —
>>> Roman
>>> 
>>>> On May 1, 2017, at 3:50 PM, Jon Haddad <jonathan.haddad@gmail.com <mailto:jonathan.haddad@gmail.com>>
wrote:
>>>> 
>>>> Sure, you could use DNS.  Where does it say IP addresses are a requirement?
>>>> 
>>>>> On May 1, 2017, at 1:36 PM, Roman Naumenko <roman@sproutling.com <mailto:roman@sproutling.com>>
wrote:
>>>>> 
>>>>> If I understand how Cassandra nodes work, they must contain a list of
seed’s IP addressed in config file.
>>>>> 
>>>>> This requirement makes cluster setup unnecessarily complicated. Is it
possible to use DNS name for seed nodes?
>>>>> 
>>>>> Thanks,
>>>>> 
>>>>> —
>>>>> Roman
>>>>> ---------------------------------------------------------------------
>>>>> To unsubscribe, e-mail: user-unsubscribe@cassandra.apache.org <mailto:user-unsubscribe@cassandra.apache.org>
>>>>> For additional commands, e-mail: user-help@cassandra.apache.org <mailto:user-help@cassandra.apache.org>
>>>>> 
>>>> 
>>> 
>> 
> 


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