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

[Dejan Muhamedagic]

On Wed, Jun 16, 2010 at 11:07:40AM +0200, Andrew Beekhof wrote:
> 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.

Yes, I just wanted to know about the meaning, because
Vadym obviously have different expectations.

I'm still not sure about the brackets. It would be beneficial to
have them as that would stress that the resources in a set have
to be specified in a different order, i.e. if there's say a
collocation like this:

collocation c1 <sc>: p2 p1

and the user wants to add p3 then that would have to be:

collocation c1 <sc>: [ p1 p2 p3 ]

Thanks,

Dejan

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