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

[Dejan Muhamedagic]

On Tue, Jun 15, 2010 at 04:44:31PM -0400, Vadym Chepkov wrote:
> 
> On Jun 15, 2010, at 3:55 PM, Dejan Muhamedagic wrote:
> 
> > On Tue, Jun 15, 2010 at 03:41:17PM -0400, Vadym Chepkov wrote:
> >> 
> >> On Jun 15, 2010, at 3:36 PM, Dejan Muhamedagic wrote:
> >> 
> >>> Hi,
> >>> 
> >>> On Tue, Jun 15, 2010 at 08:45:37AM -0400, Vadym Chepkov wrote:
> >>>> 
> >>>> On Jun 15, 2010, at 6:14 AM, Dejan Muhamedagic wrote:
> >>>> 
> >>>>> Hi,
> >>>>> 
> >>>>> On Tue, Jun 15, 2010 at 10:57:47AM +0200, Andrew Beekhof wrote:
> >>>>>> On Tue, Jun 15, 2010 at 10:23 AM, Andreas Kurz <andreas.kurz at linbit.com> wrote:
> >>>>>>> On Tuesday 15 June 2010 08:40:58 Andrew Beekhof wrote:
> >>>>>>>> On Mon, Jun 14, 2010 at 4:22 PM, Vadym Chepkov <vchepkov at gmail.com> wrote:
> >>>>>>>>> On Jun 7, 2010, at 8:04 AM, Vadym Chepkov wrote:
> >>>>>>>>>> I filed bug 2435, glad to hear "it's not me"
> >>>>>>>>> 
> >>>>>>>>> Andrew closed this bug
> >>>>>>>>> (http://developerbugs.linux-foundation.org/show_bug.cgi?id=2435) as
> >>>>>>>>> resolved, but I respectfully disagree.
> >>>>>>>>> 
> >>>>>>>>> I will try to explain a problem again in this list.
> >>>>>>>>> 
> >>>>>>>>> lets assume you want to have several resources running on the same node.
> >>>>>>>>> They are independent, so if one is going down, others shouldn't be
> >>>>>>>>> stopped. You would do this by using a resource set, like this:
> >>>>>>>>> 
> >>>>>>>>> primitive dummy1 ocf:pacemaker:Dummy
> >>>>>>>>> primitive dummy2 ocf:pacemaker:Dummy
> >>>>>>>>> primitive dummy3 ocf:pacemaker:Dummy
> >>>>>>>>> colocation together inf: ( dummy1 dummy2 dummy3 )
> >>>>>>>>> 
> >>>>>>>>> and I expect them to run on the same host, but they are not and I
> >>>>>>>>> attached hb_report to the case to prove it.
> >>>>>>>>> 
> >>>>>>>>> Andrew closed it with the comment "Thats because you have
> >>>>>>>>> sequential="false" for the colocation set." But sequential="false" means
> >>>>>>>>> doesn't matter what order do they start.
> >>>>>>>> 
> >>>>>>>> No.  Thats not what it means.
> >>>>>>>> And I believe I should know.
> >>>>>>>> 
> >>>>>>>> It means that the members of the set are NOT collocated with each
> >>>>>>>> other, only with any preceding set.
> >>>>>>> 
> >>>>>>> Just for clarification:
> >>>>>>> 
> >>>>>>> colocation together inf: ( dummy1 dummy2 dummy3 ) dummy4
> >>>>>>> 
> >>>>>>> .... is a shortcut for:
> >>>>>>> 
> >>>>>>> colocation together1 inf: dummy4 dummy1
> >>>>>>> colocation together1 inf: dummy4 dummy2
> >>>>>>> colocation together1 inf: dummy4 dummy3
> >>>>>>> 
> >>>>>>> ... is that correct?
> >>>>>> 
> >>>>>> Only if sequential != false.
> >>>>> 
> >>>>> You wanted to say "sequential == false"?
> >>>>> 
> >>>>>> For some reason the shell appears to be setting that by default.
> >>>>> 
> >>>>> This is sequential == false:
> >>>>> 
> >>>>> colocation together inf: ( dummy1 dummy2 dummy3 ) dummy4
> >>>>> 
> >>>>> This is sequential == true:
> >>>>> 
> >>>>> colocation together inf: dummy1 dummy2 dummy3 dummy4
> >>>>> 
> >>>>> Thanks,
> >>>>> 
> >>>>> Dejan
> >>>> 
> >>>> 
> >>>> I guess colocation syntax needs to be expanded to allow something like this
> >>>> 
> >>>> colocation only-one -inf: (dummy1 dummy2 sequential="true")
> >>>> 
> >>>> colocation together 5000: (dummy1 dummy2 sequential="true")
> >>> 
> >>> How's this different from a regular constraint?
> >>> 
> >> 
> >> 
> >> Because it does not create a resource set with two resources
> >> and if you put it in parentheses, it creates set with sequential="false"
> > 
> > What I meant was what is the difference between these two:
> > 
> > <rsc_colocation id="c1" rsc="p1" score="500" with-rsc="p2"/>
> > 
> > <rsc_colocation id="c1" score="500">
> > <resource_set id="c1-0">
> >  <resource_ref id="p1"/>
> >  <resource_ref id="p2"/>
> > </resource_set>
> > </rsc_colocation>
> > 
> 
> I take it there is no difference for the positive score, 
> it just looks like former looks like there is a dependency of p1 on p2.
> 
> But there is a definite difference with a negative score, 
> 
> if you have something like this
> 
> colocation only-one -inf: dummy1 dummy2
> 
> so you don't want to have them to run on the same host ever.

> and the host with dummy2 goes down.
> Instead of just not starting dummy2 anywhere it will kill dummy1 too and start dummy2 on the surviving host.
> That's an outage and not what I wanted to achieve.

Obviously that's not "ever", it's only if there's more than one
node on which they can run. If you put
 
	colocation only-one -10: dummy1 dummy2

instead, you should get what you wanted.

Thanks,

Dejan

> Vadym
> 
> 
> 
> 
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