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From Jonathan Ballet <jbal...@edgelab.ch>
Subject Re: How seed nodes are working and how to upgrade/replace them?
Date Tue, 08 Jan 2019 15:39:18 GMT
On Mon, 7 Jan 2019 at 16:51, Oleksandr Shulgin <oleksandr.shulgin@zalando.de>
wrote:

> On Mon, Jan 7, 2019 at 3:37 PM Jonathan Ballet <jballet@edgelab.ch> wrote:
>
>>
>> I'm working on how we could improve the upgrades of our servers and how
>> to replace them completely (new instance with a new IP address).
>> What I would like to do is to replace the machines holding our current
>> seeds (#1 and #2 at the moment) in a rolling upgrade fashion, on a regular
>> basis:
>>
>> * Is it possible to "promote" any non-seed node as a seed node?
>>
>> * Is it possible to "promote" a new seed node without having to restart
>> all the nodes?
>>   In essence, in my example that would be:
>>
>>   - decide that #2 and #3 will be the new seed nodes
>>   - update all the configuration files of all the nodes to write the IP
>> addresses of #2 and #3
>>   - DON'T restart any node - the new seed configuration will be picked up
>> only if the Cassandra process restarts
>>
>
> You can provide a custom implementation of the seed provider protocol:
> org.apache.cassandra.locator.SeedProvider
>
> We were exploring that approach few years ago with etcd, which I think
> provides capabilities similar to that of Consul:
> https://github.com/a1exsh/cassandra-etcd-seed-provider/blob/master/src/main/java/org/zalando/cassandra/locator/EtcdSeedProvider.java
>

Hi Alex,

we were using also a dedicated Consul seed provider but we weren't
confident enough about maintaining our version so we removed it in favor of
something simpler.
Ultimately, we hope(d) that delegating the maintenance of that list to an
external process (like Consul Template), directly updating the
configuration file, is (should be?) mostly similar without having to
maintain our own copy, built with the right version of Cassandra, etc.

Thanks for the info though!

 Jonathan

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