[ClusterLabs] Does anyone use clone instance constraints from pacemaker-next schema?

[Andrei Borzenkov]

11.01.2018 19:21, Ken Gaillot пишет:
> On Thu, 2018-01-11 at 01:16 +0100, Jehan-Guillaume de Rorthais wrote:
>> On Wed, 10 Jan 2018 12:23:59 -0600
>> Ken Gaillot <kgaillot at redhat.com> wrote:
>> ...
>>> My question is: has anyone used or tested this, or is anyone
>>> interested
>>> in this? We won't promote it to the default schema unless it is
>>> tested.
>>>
>>> My feeling is that it is more likely to be confusing than helpful,
>>> and
>>> there are probably ways to achieve any reasonable use case with
>>> existing syntax.
>>
>> For what it worth, I tried to implement such solution to dispatch
>> mulitple
>> IP addresses to slaves in a 1 master 2 slaves cluster. This is quite
>> time
>> consuming to wrap its head around sides effects with colocation,
>> scores and
>> stickiness. My various tests shows everything sounds to behave
>> correctly now,
>> but I don't feel really 100% confident about my setup.
>>
>> I agree that there are ways to achieve such a use case with existing
>> syntax.
>> But this is quite confusing as well. As instance, I experienced a
>> master
>> relocation when messing with a slave to make sure its IP would move
>> to the
>> other slave node...I don't remember exactly what was my error, but I
>> could
>> easily dig for it if needed.
>>
>> I feel like it fits in the same area that the usability of Pacemaker.
>> Making it
>> easier to understand. See the recent discussion around the gocardless
>> war story.
>>
>> My tests was mostly for labs, demo and tutorial purpose. I don't have
>> a
>> specific field use case. But if at some point this feature is
>> promoted
>> officially as preview, I'll give it some testing and report here
>> (barring the
>> fact I'm actually aware some feedback are requested ;)).
> 
> It's ready to be tested now -- just do this:
> 
>  cibadmin --upgrade
>  cibadmin --modify --xml-text '<cib validate-with="pacemaker-next"/>'
> 
> Then use constraints like:
> 
>  <rsc_colocation id="id0" score="100"
>    rsc="rsc1"
>    with-rsc="clone1" with-rsc-instance="1" />
> 
>  <rsc_colocation id="id1" score="100"
>    rsc="rsc2"
>    with-rsc="clone1" with-rsc-instance="2" />
> 
> to colocate rsc1 and rsc2 with separate instances of clone1. There is
> no way to know *which* instance of clone1 will be 1, 2, etc.; this just
> allows you to ensure the colocations are separate.
> 

Is it possible to designate master/slave as well?

> Similarly you can use rsc="clone1" rsc-instance="1" to colocate a clone
> instance relative to another resource instead.
> 
> For ordering, the corresponding syntax is "first-instance" or "then-
> instance" as desired.
> 
> I believe crm shell has higher-level support for this feature.
> 
> Personally, I think standard colocations of rsc1 and rsc2 with clone1,
> and then an anticolocation between rsc1 and rsc2, would be more
> intuitive. You're right that the interactions with stickiness etc. can
> be tricky, but that would apply to the alternate syntax as well.
>