[Pacemaker] Shouldn't colocation -inf: be mandatory?

[Andrew Beekhof]

On Wed, Jun 16, 2010 at 10:29 AM, Dejan Muhamedagic <dejanmm at fastmail.fm> wrote:
> Hi,
>
> On Wed, Jun 16, 2010 at 08:55:26AM +0200, Andrew Beekhof wrote:
>> On Tue, Jun 15, 2010 at 9:41 PM, Dejan Muhamedagic <dejanmm at fastmail.fm> wrote:
>>
>> > colocation not-together -inf: d1 d2 d3
>>
>> I think there is a problem with this syntax, particularly for +inf.
>>
>> Consider:
>>   colocation together1 inf: d1 d2
>>
>> This means d1 must run where d2 is.
>>
>> But if I add d3:
>>   colocation together1 inf: d1 d2 d3
>>
>> Now the original constraint is reversed and d2 must run where d1 is
>> (think of how groups work).
>> (Unless you're modifying the order).
>
> No, the order is not modified.
>
>> I think we need:
>>    no brackets: exactly 2 resources must be specified
>>    () brackets: a non-sequential set
>>    [] brackets: a sequential set
>
> I thought that the sets were supposed to reduce the number of
> constraints and to be used in case more than three resources
> involved. That's why there's no special notation for the
> sequential sets: there would be simply more than two resources.
>
> If we adopt the above notation, is there a semantic difference
> between these two:
>
> order o1 <sc>: p1 p2
> order o2 <sc>: [ p2 p1 ]
>
> or these two:
>
> collocation c1 <sc>: p2 p1
> collocation c2 <sc>: [ p1 p2 ]

They'd effectively do the same thing, but the first form would always
result in a "normal" constraint, the second always a set.