[Pacemaker] [pacemaker][patch 3/4] Simple changes for "Pacemaker Explained", Chapter 6 CH_Constraints.xml
Andrew Beekhof
andrew at beekhof.net
Mon Apr 11 09:41:53 EDT 2011
On Mon, Apr 11, 2011 at 2:33 PM, Tim Serong <tserong at novell.com> wrote:
>> >> > 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
>>
>> Given the well discussed issues with the shell syntax, I'd prefer to
>> see the raw xml actually.
>
> <constraints>
> <rsc_colocation id="c" score="INFINITY">
> <resource_set id="c-0">
> <resource_ref id="F"/>
> <resource_ref id="G"/>
> </resource_set>
> <resource_set id="c-1" sequential="false">
> <resource_ref id="C"/>
> <resource_ref id="D"/>
> <resource_ref id="E"/>
> </resource_set>
> <resource_set id="c-2">
> <resource_ref id="A"/>
> <resource_ref id="B"/>
> </resource_set>
> </rsc_colocation>
> </constraints>
So, at least for colocation, it looks like we want either the order
within the set to be the reverse of what it is now.
Ie.
<resource_set id="c-2">
<resource_ref id="B"/>
<resource_ref id="A"/>
</resource_set>
Or the order of the sets reversed (so as to work like groups).
Ie.
<resource_set id="c-2">
<resource_ref id="A"/>
<resource_ref id="B"/>
</resource_set>
<resource_set id="c-1" sequential="false">
<resource_ref id="C"/>
<resource_ref id="D"/>
<resource_ref id="E"/>
</resource_set>
<resource_set id="c-0">
<resource_ref id="F"/>
<resource_ref id="G"/>
</resource_set>
Which do people think is going to be more comprehendible?
Since we want new behavior, we should use a new syntax to be able to
distinguish between the two.
Which is handy because the existing syntax is clearly challenging.
At a minimum we want s/resource_set/colocation_set/g
Two additional open questions, How to indicate the scores:
- between the sets
Keep using the score from the constraint?
- between resources within a set (sequential is clearly too confusing).
Perhaps with internal_score and external_score attributes for colocation_set's.
Where the value of external_score on colocation_set N reflects the
colocation preference with set N-1 (ie. the one above it in xml
syntax).
And also:
- how to deal with roles and instances sanely?
In pseudo DTD syntax, I think we're looking at something like:
colocation_set ::= id, resource_ref+, internal_score?
resource_ref ::= id-ref, action?, role?, instance?
With the whole between sets thing to be still worked out.
>> > # 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.
>> >> >
>> >> >
>> >> >
>> >> >
>> >> > _______________________________________________
>> >> > Pacemaker mailing list: Pacemaker at oss.clusterlabs.org
>> >> > 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.
>> >
>> >
>> >
>> > _______________________________________________
>> > Pacemaker mailing list: Pacemaker at oss.clusterlabs.org
>> > 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.
>
>
>
> _______________________________________________
> Pacemaker mailing list: Pacemaker at oss.clusterlabs.org
> 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
>
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