[ClusterLabs] starting primitive resources of a group without starting the complete group - unclear behaviour

[Ken Gaillot]

On 04/21/2017 04:38 AM, Lentes, Bernd wrote:
> 
> 
> ----- On Apr 21, 2017, at 1:24 AM, Ken Gaillot kgaillot at redhat.com wrote:
> 
>> On 04/20/2017 02:53 PM, Lentes, Bernd wrote:
> 
>>
>> target-role=Stopped prevents a resource from being started.
>>
>> In a group, each member of the group depends on the previously listed
>> members, same as if ordering and colocation constraints had been created
>> between each pair. So, starting a resource in the "middle" of a group
>> will also start everything before it.
> 
> What is the other way round ? Starting the first of the group ? Will the subsequent follow ?

Groups are generally intended to start and stop as a whole, so I would
expect starting any member explicitly to lead the cluster to want to
start the entire group, but I could be wrong, because only prior members
are required to be started first.

>> Everything in the group inherits this target-role=Stopped. However,
>> prim_vnc_ip_mausdb has its own target-role=Started, which overrides that.
>>
>> I'm not sure what target-role was on each resource at each step in your
>> tests, but the behavior should match that.
>>
> 
> I have to admit that i'm struggling with the meaning of "target-role".
> What does it really mean ? The current status of the resource ? The status of the resource the cluster should try
> to achieve ? Both ? Nothing of this ? Could you clarify that to me ?

"try to achieve"

The cluster doesn't have any direct concept of intentionally starting or
stopping a resource, only of a desired cluster state, and it figures out
the actions needed to get there. The higher-level tools provide the
start/stop concept by setting target-role.

It's the same in practice, but the cluster "thinks" in terms of being
told what the desired end result is, not what specific actions to perform.

> 
> Thanks.
> 
> 
> Bernd
>  
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