[Pacemaker] [pacemaker][patch 3/4] Simple changes for "Pacemaker Explained", Chapter 6 CH_Constraints.xml

[Tim Serong]

On 4/11/2011 at 09:37 PM, Andrew Beekhof <andrew at beekhof.net> wrote: 
> On Mon, Apr 11, 2011 at 12:57 PM, Tim Serong <tserong at novell.com> wrote: 
> > On 3/21/2011 at 08:20 PM, Andrew Beekhof <andrew at beekhof.net> wrote: 
> >> 
> >> Small improvement to: 
> >> +     The only thing that matters is that in order for any member of a set 
> >> to be active, all the members of the previous set must also be active 
> >> (and naturally on the same node). When a set has 
> >> <literal>sequential="true"</literal>, then in order for any member to 
> >> be active, the previous members must also be active. 
> >> 
> >> +     The only thing that matters is that in order for any member of a set 
> >> to be active, all the members of the previous set<footnote><para>as 
> >> determined by the display order in the configuration</para></footnote> 
> >> must also be active (and naturally on the same node). 
> >> + When a set has <literal>sequential="true"</literal>, then in order 
> >> for any member to be active, the previous members must also be active. 
> > 
> > This isn't quite correct. 
> > 
> > For members within a set (sequential=true), it is true that for a given 
> > member to be active, the previous members must also be active. 
> > 
> > Between sets however, it's the other way around - a given set depends on 
> > the subsequent set. 
>  
> Did I really write it like that? You tested it?

Yup.  Well, I tested it (pcmk 1.1.5), so I assume you wrote it like that :)

We want (pardon the ASCII art):

             /--> C --\
  G --> F --+---> D ---+--> B --> A
             \--> E --/

Test is:

  # crm configure colocation c inf: F G ( C D E ) A B
  # crm resource stop F
     (stops F and G)
  # crm resource start F
  # crm resource stop D
     (stops D, F and G)
  # crm resource start D
  # crm resource stop B
     (stops everything except A)

That shell colocation constraint maps exactly to the (new) XML shown below
(verified just in case it turned out to be a shell oddity).

> If so, thats just retarded and needs an overhaul. 

It is a little... confusing.

Regards,

Tim

> > 
> > The example colocation chain in Pacemaker Explained right now should thus 
> > be changed as follows in order to match the diagram: 
> > 
> >  <constraints> 
> >    <rsc_colocation id="coloc-1" score="INFINITY" > 
> >       <resource_set id="collocated-set-1" sequential="true"> 
> > -        <resource_ref id="A"/> 
> > -        <resource_ref id="B"/> 
> > +        <resource_ref id="F"/> 
> > +        <resource_ref id="G"/> 
> >      </resource_set> 
> >      <resource_set id="collocated-set-2" sequential="false"> 
> >        <resource_ref id="C"/> 
> >        <resource_ref id="D"/> 
> >        <resource_ref id="E"/> 
> >      </resource_set> 
> >      <resource_set id="collocated-set-2" sequential="true" role="Master"> 
> > -        <resource_ref id="F"/> 
> > -        <resource_ref id="G"/> 
> > +        <resource_ref id="A"/> 
> > +        <resource_ref id="B"/> 
> >      </resource_set> 
> >    </rsc_colocation> 
> >  </constraints> 
> > 
> > Regards, 
> > 
> > Tim 
> > 
> > 
> > -- 
> > Tim Serong <tserong at novell.com> 
> > Senior Clustering Engineer, OPS Engineering, Novell Inc. 
> > 
> > 
> > 
> > 
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> > http://oss.clusterlabs.org/mailman/listinfo/pacemaker 
> > 
> > Project Home: http://www.clusterlabs.org 
> > Getting started: http://www.clusterlabs.org/doc/Cluster_from_Scratch.pdf 
> > Bugs:  
> http://developerbugs.linux-foundation.org/enter_bug.cgi?product=Pacemaker 
> > 
>  




-- 
Tim Serong <tserong at novell.com>
Senior Clustering Engineer, OPS Engineering, Novell Inc.