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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 06:43:19 GMT
...and come to think of it, there is another question. Cloud instance
tags are simply labels. There is no real semantics associated or
mandated by tags.

In particular, there is no guarantee that a Zk instance is running on,
e.g., an EC2 instance labelled as "Zookeeper". Tags don't make services.

If you want to use auto-scaling to create more Zk nodes and reconfigure
an existing cluster, the cluster will take care of discovering its
members, so only clients would be affected by the changes. They, however
could start with a well-known set of Zk nodes (e.g., the initial three),
inquire about the actual configuration, and subscribe to configuration
changes. There is no need for a tag- or DNS-based grouping this way.

If you wanted to say, "hey, all of you Zk instances in my VPC, form a
cluster right now", you could do this indeed with tagging to seed the
server list initially. However, keep in mind that Zk is often a
security-relevant component and you don't really want ANY new Zk server
out there to be able to join your precious cluster - only the ones you
know about already.

The fact that Consul may support something like it, doesn't mean it also
makes sense for Zookeeper. Consul and Zookeeper protocols and
architectures are quite different.

I still don't understand what the precise requirement is that lead to
this question.

I hope you'll enlighten me :-)

Cheers,

--Jürgen


On 11.02.2019 01:20, rammohan ganapavarapu wrote:

> Should I open a feature request? For both cloud auto discovery and use DNS
> end point to form a quorum.
>
> On Sun, Feb 10, 2019, 3:56 PM Alan Scherger <alan.scherger@gmail.com> wrote:
>
>> We might look at something like this: https://github.com/hekate-io/hekate
>> for inspiration (or adoption). In the Golang community Hashicorp has built
>> something similar: https://github.com/hashicorp/go-discover -- this
>> problem
>> set itself probably warrants a multilingual Apache project to help drive
>> some standards and interoperability.
>>
>> Alan
>>
>> On Sun, Feb 10, 2019, 5:42 PM rammohan ganapavarapu <
>> rammohanganap@gmail.com
>> 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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