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But without this separation on orchestration layer, we are unable to
differentiate between nodes.
What i mean is - we need to run subset of tasks on primary first and then
on all others, and we are using role as mapper
to node identities (and this mechanism was hardcoded in nailgun for a long
time).

Lets say we have task A that is mapped to primary-controller and B that is
mapped to "secondary" controller, task B requires task A.
If there is no primary in mapping - we will execute task A on all
controllers and then task B on all controllers.

And how in such case deployment code will know that it should not execute
commands in task A for "secondary" controllers and
in task B on "primary" ?

On Wed, Jan 28, 2015 at 10:44 AM, Sergii Golovatiuk <
sgolovatiuk at mirantis.com> wrote:

> Hi,
>
> *But with introduction of plugins and granular deployment, in my opinion,
> we need to be able*
> *to specify that task should run specifically on primary, or on
> secondaries. Alternative to this approach would be - always run task on all
> controllers, and let task itself to verify that it is  executed on primary
> or not.*
>
> I wouldn't differentiate tasks for primary and other controllers.
> "Primary-controller" logic should be controlled by task itself. That will
> allow to have elegant and tiny task framework ...
>
> --
> Best regards,
> Sergii Golovatiuk,
> Skype #golserge
> IRC #holser
>
> On Tue, Jan 27, 2015 at 11:35 PM, Dmitriy Shulyak <dshulyak at mirantis.com>
> wrote:
>
>> Hello all,
>>
>> You may know that for deployment configuration we are serializing
>> additional prefix for controller role (primary), with the goal of
>> deployment order control (primary-controller always should be deployed
>> before secondaries) and some condiions in fuel-library code.
>>
>> However, we cannot guarantee that primary controller will be always the
>> same node, because it is not business of nailgun to control elections of
>> primary. Essentially user should not rely on nailgun
>> information to find primary, but we need to persist node elected as
>> primary in first deployment
>> to resolve orchestration issues (when new node added to cluster we should
>> not mark it as primary).
>>
>> So we called primary-controller - "internal" role, which means that it is
>> not exposed to users (or external developers).
>> But with introduction of plugins and granular deployment, in my opinion,
>> we need to be able
>> to specify that task should run specifically on primary, or on
>> secondaries. Alternative to this approach would be - always run task on all
>> controllers, and let task itself to verify that it is  executed on primary
>> or not.
>>
>> Is it possible to have significantly different sets of tasks for
>> controller and primary-controller?
>> And same goes for mongo, and i think we had primary for swift also.
>>
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>
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