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From Jürgen Wagner (DVT) <juergen.wag...@devoteam.com.INVALID>
Subject Re: RR DNS name instead of list of server
Date Mon, 11 Feb 2019 03:21:21 GMT
Hello all,

  I've been following this discussion, and there seem to be some
misconceptions or wrong assumptions involved, esp. as Consul does have a
different architecture from Zookeeper.

First of all, it is unclear to me what exactly the goal of this should
be. It sounds a bit like jumping in the midst of a discussion without
knowing what it is really about originally. Therefore, I have a few
general remarks, some of which may already provide a hint to address the
original challende the OP is facing.

- I recommend having a look at the dynamic reconfiguration feature of
Zookeeper. This will allow changing clusters., e.g., the addition of nodes.

- If you have a Zookeeper cluster, you'd like to not start new and kill
old Zookeeper pods all the time, have changing IP addresses and all
that, but keep them reliable. Therefore, I don't see the benefit of RR
DNS names in the Zookeeper configuration AT ALL. Why would you need any
form of discovery between the Zk nodes if they have their own
cluster-forming and election protocols?

- Clients will receive a list of Zk node names and can also inquire the
cluster in case of reconfigurations, but will then randomly make choices
from that list to connect to a cluster. There is no need for RR here.
You will already get balanced access.

- RR on the DNS level or a dumb load balancer is not a good idea for
session-oriented protocols, anyway.

So, Ram, can you explain once more why you want RR DNS in the first
place? What do you want to achieve really?



On 11.02.2019 00:42, rammohan ganapavarapu wrote:
> Clod providers have api to query instance IP based in tags, actually consul
> is doing that to form a cluster.
> On Sun, Feb 10, 2019, 11:40 AM Andor Molnar <andor@cloudera.com.invalid>
> wrote:
>> Hi Ram!
>> What exactly do you mean by "auto-discovery on cloud instance tags"?
>> Is there a standard way of doing that?
>> Regards,
>> Andor
>> On Sat, Feb 9, 2019 at 4:07 PM Norbert Kalmar <nkalmar@cloudera.com.invalid
>> wrote:
>>> Hi Ram,
>>> Unfortunately ZK does not support RR DNS name.
>>> As for plans on discovery based on cloud tags, I am not aware of any
>> plans.
>>> You can create a jira for it if you'd like, but I can't tell you when
>> that
>>> would make it into a release.
>>> Regards,
>>> Norbert
>>> On Fri, Feb 8, 2019 at 11:53 PM rammohan ganapavarapu <
>>> rammohanganap@gmail.com> wrote:
>>>> Hi,
>>>> Does zookeper support RR DNS name in the config instead of giving each
>>>> server name/ip like what consul does to join the cluster?
>>>> server.1=server1
>>>> server.2=server2
>>>> server.3=server3
>>>> vs
>>>> server=example.com
>>>> where example.com is RR of server1, server2 and server3
>>>> And does any one know if zk team has any plans to add cloud
>> autodiscovery
>>>> based on cloud instance tags?
>>>> Thanks,
>>>> Ram

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