[Pacemaker] Dependency Trees

[Dejan Muhamedagic]

On Tue, Feb 26, 2013 at 11:31:52AM +1100, Andrew Beekhof wrote:
> On Tue, Feb 26, 2013 at 2:00 AM, Dejan Muhamedagic <dejanmm at fastmail.fm> wrote:
> > On Fri, Feb 22, 2013 at 11:39:52AM +1100, Andrew Beekhof wrote:
> >> On Fri, Feb 22, 2013 at 1:40 AM, Donald Stahl <don at blacksun.org> wrote:
> >> >> No.
> >> >>
> >> >> [quote]
> >> >> If you say "colocate A with B" and there is nowhere B is allowed to
> >> >> run, then A wont be allowed to run either.
> >> >> But once the cluster has figured out where they go, it doesn't stop
> >> >> them being started in parallel.
> >> >> [/quote]
> >> >>
> >> >> in this case, A = OraListener1 and B = OraBin1
> >> >>
> >> >> You only get the "Start A then start B" part by adding the ordering constraint.
> >> >
> >> > I'm not sure I understand where the "sequential" option comes into
> >> > play with a colocation set then.
> >> >
> >> > Or to put it another way- I'm not sure what practical difference there
> >> > is in these examples:
> >> >
> >> > http://clusterlabs.org/wiki/FAQ#Collocation_Sets
> >> >
> >> > colocation myset inf: app1 app2
> >> > colocation myset inf: ( app1 app2 )
> >>
> >> I'm pretty sure the latter doesn't do anything (bad choice of defaults
> >> by the crmsh) because the set isn't colocated with anything.
> >
> > Bad? Choice? What is there for crmsh to choose?
> 
> Defaulting sequential to false for sets, because you didn't take the
> time to understand what anything meant.

( rsc1 rsc2 ... ) means sequential=false. If you want sequential,
then remove the parentheses. Or is there anything I'm missing here?

Thanks,

Dejan

> 
> > This is what is
> > produced:
> >
> >       <rsc_colocation id="s1" score="INFINITY">
> >         <resource_set id="s1-0" sequential="false">
> >           <resource_ref id="d1"/>
> >           <resource_ref id="d2"/>
> >         </resource_set>
> >       </rsc_colocation>
> >
> > Whether that makes sense is another matter.
> >
> > Thanks,
> >
> > Dejan
> >
> >> You'd need something as well as the set for it to make sense,  eg.
> >>
> >>    colocation myset inf: app0 ( app1 app2 )
> >>
> >> > The first seems to say that app1 is dependent on app2 being able to
> >> > run somewhere.
> >> >
> >> > Does the second one simply say that they must not be split up, but if
> >> > only one can run, that's fine?
> >> >
> >> > -Don
> >> >
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> >
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