Implementing Juju Actions

[William Reade]

We should not be using juju run to implement juju actions; they should be
fed to the uniter analogously to hooks.

On Thu, Mar 27, 2014 at 1:32 PM, Gustavo Niemeyer <gustavo at niemeyer.net>wrote:

> On Thu, Mar 27, 2014 at 6:53 AM, Tim Penhey <tim.penhey at canonical.com>
> wrote:
> > The outline that Gustavo has given has actions fit into this world view.
>
> Indeed. Because that's the way that sounds reasonable, but I'm open to
> arguments about why that's not the case.
>

I am entirely on board with your interpretation of this issue. Juju run
works that way out of expediency, not conceptual purity or correctness. The
ideal implementation of juju actions would probably end up replacing the
client-side implementation of juju-run, in favour of storing run commands
as (pseudo-)actions themselves.


> It's the same problem of internal service coordination. A leader must
> be elected to take responsibility for procedures on behalf of the
> service.


Agreed; actions absolutely can and should target services, but it's
possible to make progress on unit actions without worrying about that too
much. I would expect us to run service actions on the leader unit, probably
in a different execution context that could, if necessary, made additional
tools available for managing cross-unit coordination. If you're at risk of
becoming blocked on in-juju leader election, let us know and we will try to
expedite it.

James, I think Gustavo's suggestion that you take a look at the Config is
good, because it would be sensible to use the same pathways for configuring
actions as we already do for charms. By following the path of that data
from `deploy` and `set`, over the API, into state, and back out over the
API to the unit agents, you should get a pretty good idea of one half of
the task; the other half, of tweaking the Uniter state machine to respond
to these new request kinds in a sane way, will probably demand a separate
discussion.

Cheers
William
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