[Linux-HA] resource group design question (2)

[Andrew Beekhof]

On 10/12/07, Daniel X Moore <dxm at sgi.com> wrote:
> Andrew Beekhof wrote:
> >> But this prevents us from adding/removing sub-resources
> >> effectively as HB knows nothing of them.
> >
> > in what way does HB prevent this?
> > if you change the value then we'll tell your resource the new value.
>
> The _new_ value, yes. Not the old, so the plugin doesn't know what to
> stop (if any).

if the attribute is "reloadable" then yes (you could always store it
somewhere though)
otherwise we'll send you a stop with the old value and a start with the new one

>
> Also, there's no way for the program which makes the change to
> synchronize against the plugin starting/stopping the sub-resource. eg:
> you add a sub-resource, but there's no way to ask HB when that change
> has actually taken effect.

why ask HB? - you're the one starting it... wouldn't you know when its done?

>
> >>> I'm really interested in that use case. It's morning here and I
> >>> can only imagine that you want to dynamically order the way the
> >>> parts are handled.
> >> Each resource within the group needs a number of sub-resources
> >> started/stopped and the sequence is mixed up between the resources when
> >> starting/stopping everything together.
> >
> > define "mixed up"
>
> Each sub-resource has a number of phases for start & stop. We need to
> run one phase for each sub-resource, then the next phase for each
> sub-resource etc. -> we need to know the list of sub-resources so we can
> process them together.

fancyRAstart() {
for subrsc in rsclist; do
   phase1start
done

for subrsc in rsclist; do
   phase2start
done

...

}


and presumably the reverse for stop.  no?

>
> >> Hope this explains it!
> >
> > not really - but maybe i'm thick
>
> more likely, I'm not explaining it properly. It'd be easy with a
> white-board.

ok... draw me a couple of gifs or powerpoint slides :-)