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From Jeff Jirsa <jji...@gmail.com>
Subject Re: How seed nodes are working and how to upgrade/replace them?
Date Tue, 08 Jan 2019 17:29:01 GMT
Given Consul's popularity, seems like someone could make an argument that
we should be shipping a consul-aware seed provider.


On Tue, Jan 8, 2019 at 7:39 AM Jonathan Ballet <jballet@edgelab.ch> wrote:

> 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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