machine placement spec

[William Reade]

On Fri, 2011-11-11 at 12:20 +0100, William Reade wrote:
> On Thu, 2011-11-10 at 16:14 -0200, Gustavo Niemeyer wrote:
> > > The idea was:
> > >
> > >  juju deploy foo -c ram=512M -c "orchestra-classes=blib blob blub"
> > >
> > > Bad idea, or just badly expressed?
> > 
> > Bad idea. We should be able to express multiple constraints next to
> > each other for several reasons (think charms and stacks).
> 
> Expand please? If we're expressing them in stacks or charms I think I'd
> rather have a yaml list of distinct constraints than to smush them all
> together and have to parse them out myself, and to my eye it's quite
> convenient and readable to have a separate command-line option for each
> constraint.

Additional thought: when specifying them all together in one chunk,
there's a subtle implication that we're specifying a full set of
constraints and that no parent constraints apply. There's a case to be
made for this approach, but nobody's questioned the inheritance approach
yet; IMO, requiring distinct options for distinct constraints is a
better cognitive fit in this case.