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<div>Please do not merge colocation and order together in a way that only none or both is present.</div>
<div> </div>
<div>Example 1: Resource A communicates with resource B over network but A must run before B.</div>
<div>In this case only order is needed without colocation.</div>
<div> </div>
<div>Example 2: Resource A and B share a local directory structure.</div>
<div>In this case they must run on the same node with colocation, but order is not important.</div>
<div> </div>
<div>
<div>chain A B</div>
<div>does neither fit example 1 nor 2.</div>
<div> </div>
<div>It is OK to have chain additional, but dont remove order and/or colocation.</div>
<div>Or chain is extended to allow specify only order or only colocation.</div>
<div> </div>
<div>Rainer</div>
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<div style="margin:0 0 10px 0;"><b>Gesendet:</b> Freitag, 13. Dezember 2013 um 11:57 Uhr<br/>
<b>Von:</b> "Lars Marowsky-Bree" <lmb@suse.com><br/>
<b>An:</b> "The Pacemaker cluster resource manager" <pacemaker@oss.clusterlabs.org><br/>
<b>Betreff:</b> Re: [Pacemaker] crmsh: New syntax for location constraints, suggestions / comments</div>
<div name="quoted-content">On 2013-12-13T11:46:05, Kristoffer Grönlund <kgronlund@suse.com> wrote:<br/>
<br/>
> This worries me as well, however the current syntax for constraints is<br/>
> confusing and error-prone.<br/>
<br/>
Right. At least the { } would make it clear to users that it's now a<br/>
resource set and not merely more than 2 in the same sequence.<br/>
<br/>
> It would be great to be able to do something<br/>
> to make this easier to use, but exactly what it would be is hard to<br/>
> say. Making a change that would silently invert the functionality of<br/>
> existing configurations is, I agree, not a good idea. However, maybe it<br/>
> would be acceptable if a "version: 2" header is required in the<br/>
> document to enable the new syntax?<br/>
<br/>
Yeah. It's one of those "I wish we had done it differently" moments, but<br/>
I guess we're stuck here.<br/>
<br/>
But another thing we discussed is hiding ids for dependencies by<br/>
default, since except for resource objects they really don't matter in<br/>
99% of the cases. That would condense the configuration significantly.<br/>
<br/>
> Yet another option is to come up with some entirely new construct to<br/>
> supplement colocation and order which does what I think most people<br/>
> intuitively expects by default, which is enforces both colocation and<br/>
> ordering, so that 'foo depends on bar' means foo will start after bar,<br/>
> and only where bar is running.<br/>
<br/>
chain a b c<br/>
<br/>
(specifying the id or a score would be optional; score would default to<br/>
mandatory.)<br/>
<br/>
I'm all in favor. ;-) I'd love it if this had backend support (so pcs<br/>
could use it too), but if we can't get it, we may just merge colocation<br/>
and order internally to crmsh.<br/>
<br/>
<br/>
Regards,<br/>
Lars<br/>
<br/>
--<br/>
Architect Storage/HA<br/>
SUSE LINUX Products GmbH, GF: Jeff Hawn, Jennifer Guild, Felix Imendörffer, HRB 21284 (AG Nürnberg)<br/>
"Experience is the name everyone gives to their mistakes." -- Oscar Wilde<br/>
<br/>
<br/>
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