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From Alexander Shraer <shra...@gmail.com>
Subject Re: ZK + dynamic config + EC2
Date Sun, 22 Nov 2015 22:25:00 GMT
Yes, unique ids require consensus (or admin), but ZK gives you this. you
could use for example the sequential flag or alternatively the set
conditional on a version.
On Nov 22, 2015 3:34 PM, "Oboturov, Artem" <artem.oboturov@zalando.de>

> There is one more thing to it: ZK has a byte range for values server IDs -
> 255 in total, how could you allocate those to instances without having a
> central registry for IDs? It could be based on IPs, but it seems there are
> no other idempotent/reliable ways to get them assigned?
> On 21 November 2015 at 20:42, Alexander Shraer <shralex@gmail.com> wrote:
>> The only issue I see is that if the new server has the same id as the old
>> one you're replacing, I think you should first remove the old one and then
>> in a separate command add the new one. Intuitively this way you avoid
>> having the newly joining server act as someone who knows the current state
>> of the system (which it doesn't), a situation that may cause you to loose
>> transactions.
>> Notice that there are two reconfig interfaces  -- incremental and bulk
>> (see manual
>> <https://zookeeper.apache.org/doc/trunk/zookeeperReconfig.html>).
>> On Sat, Nov 21, 2015 at 1:16 PM, Oboturov, Artem <
>> artem.oboturov@zalando.de> wrote:
>>> Hi
>>> I was looking at the ZK 3.5.x series new feature - dynamic configuration.
>>> As an example, we could have an EC2 auto scaling group for 3 ZK nodes.
>>> When
>>> one of them goes down, a new one would be spawned, but its IP could be
>>> different. We could query EC2 to get all instances from group and
>>> generate
>>> a config for ZK to take all currently running servers as part of ZK
>>> cluster, and then run an update of cluster configs for all existing ones
>>> using dynamic config feature. Would this strategy work? Are there any
>>> alternatives?
>>> --
>>> Regards
>>> Artem Oboturov
> --
> Regards
> Artem Oboturov

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