[Pacemaker] Dependency Trees

[Andrew Beekhof]

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.

> 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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>
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