Code review comment for lp:~johnsca/charm-helpers/multi-unit
Revision history for this message
| Benjamin Saller (bcsaller) wrote | # |
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bbfa235
(Get the code!)
On 2014/06/04 21:09:21, johnsca wrote:
> On 2014/06/04 20:57:39, benjamin.saller wrote:
> >
https:/
> > charmhelpers/
the
> default
> > unit.
> > There is a rule I try to use when generating/process data these
days, no data
> > should live in the key side of the mapping. In the context of a
template for
> > iteration is simpler to iterate
> >
> > context[
> > {_unit: 'unit/1', 'foo': bar}]
> >
> > This rule makes additional sense when thinking that knowing the unit
names to
> > request them would imply a broken charm and thus shouldn't be an
index in this
> > context. I'd suggest transitioning to that. We could also make the
rule (and
> > document here) that only elements with complete data appear in the
list.
> Can you explain your reasoning behind making use of the key? I'm not
averse to
> changing it to being a list instead of a mapping, but using a
"special" field to
> hold the unit name ('_unit', in your example) seems more dangerous,
since it
> could potentially conflict with actual fields, even if unlikely due to
the
> underscore prefix.
> With your comment that the charm shouldn't actually know / care about
the unit
> name, maybe we can just leave it out altogether, especially if it only
contains
> "complete" data sets.
I think for our use case we don't actually need the unitname at all and
could omit it, in the more general case I expect that there are cases
where people will want to delta the relation data vs previous hook calls
(cached data) before taking some actions.
The list vs dict thing is a pattern that I picked up working in the
machine learning space. It tends to be easier to consume and pivot flat
tuple style data. I was looking for a nice right up justifying this
pattern, its even known as "<someones> law" but I can't remember that
name :-/
However if the value in the key side of the mapping can't be known/used
its a good indicator to me that we can flatten the structure. Maybe not
very persuasive.
https:/