[Pacemaker] Dependency Trees

[Dejan Muhamedagic]

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? 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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