[Pacemaker] RFC: Compacting constraints

[Dejan Muhamedagic]

Hi,

On Thu, 29 Oct 2009 14:39 +0100, "Lars Marowsky-Bree" <lmb at suse.de>
wrote:
> Hi all,
> 
> I have a pretty common use case - 4-16 nodes with OCFS2 etc, hosting a
> ton of Xen/KVM guests.
> 
> Compacting the OCFS2 setup was pretty easy -
> http://www.advogato.org/person/lmb/diary.html?start=104 - and that part
> seems short enough. 
> 
> For each guest, I need an order and collocation constraint with the base
> resources, which becomes complex and lengthy very quickly. Just to
> illustrate my point:
> 
> colocation dummy1-c inf: base-clone dummy1
> colocation dummy10-c inf: base-clone dummy10
> colocation dummy11-c inf: base-clone dummy11
> colocation dummy12-c inf: base-clone dummy12
> colocation dummy13-c inf: base-clone dummy13
> colocation dummy14-c inf: base-clone dummy14
> colocation dummy15-c inf: base-clone dummy15
> colocation dummy16-c inf: base-clone dummy16
> colocation dummy17-c inf: base-clone dummy17
> colocation dummy18-c inf: base-clone dummy18
> colocation dummy19-c inf: base-clone dummy19
> colocation dummy2-c inf: base-clone dummy2
> colocation dummy3-c inf: base-clone dummy3
> colocation dummy4-c inf: base-clone dummy4
> colocation dummy5-c inf: base-clone dummy5
> colocation dummy6-c inf: base-clone dummy6
> colocation dummy7-c inf: base-clone dummy7
> colocation dummy8-c inf: base-clone dummy8
> colocation dummy9-c inf: base-clone dummy9
> order dummy1-o 0: base-clone dummy1
> order dummy10-o 0: base-clone dummy10
> order dummy11-o 0: base-clone dummy11
> order dummy12-o 0: base-clone dummy12
> order dummy13-o 0: base-clone dummy13
> order dummy14-o 0: base-clone dummy14
> order dummy15-o 0: base-clone dummy15
> order dummy16-o 0: base-clone dummy16
> order dummy17-o 0: base-clone dummy17
> order dummy18-o 0: base-clone dummy18
> order dummy19-o 0: base-clone dummy19
> order dummy2-o 0: base-clone dummy2
> order dummy3-o 0: base-clone dummy3
> order dummy4-o 0: base-clone dummy4
> order dummy5-o 0: base-clone dummy5
> order dummy6-o 0: base-clone dummy6
> order dummy7-o 0: base-clone dummy7
> order dummy8-o 0: base-clone dummy8
> order dummy9-o 0: base-clone dummy9
> 
> 
> There's a bunch of open issues (resource_sets not supporting score="0",
> the crm shell not supporting resource_sets at all),

That's on the todo list, I've even started working on it, but then had
an issue with funny way resource sets are constructed in CIB. We had a
discussion about that last year.

> but I'd even more
> prefer if I didn't have to have both the order and collocation
> constraints.
> 
> Could we introduce an "conjoin" dependency which merges both? I don't
> much care whether this is done at the XML/CIB level, or at the shell
> level (detect duplication and merge for the shell syntax - the advantage
> would be that none of the other CIB consumers would need to be taught
> about it); it should allow, of course, to specify both the ordering and
> collocation scores.
> 
> So, I'd imagine that the above could be represented in the shell syntax
> as:
> 
> conjoin dummies-dep base-clone {dummy1, dummy2, dummy3, ...} \
> 	meta score_collocation=infinity score_order=0

There are no shell constructs which are rendered as two or more CIB
elements. I guess that this should be possible, but really can't say
until I take a thorough look at the implementation. BTW, I guess that
there are other CIB phrases which are commonly in use.

Thanks,

Dejan

> This would be an extremely desirable usability improvement, IMNSHO. I
> welcome your feedback.
> 
> 
> Regards,
>     Lars
> 
> -- 
> Architect Storage/HA, OPS Engineering, Novell, Inc.
> SUSE LINUX Products GmbH, GF: Markus Rex, HRB 16746 (AG Nürnberg)
> "Experience is the name everyone gives to their mistakes." -- Oscar Wilde
> 
> 
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