Does relation scopes need to match?

[fengxia]

Just to clarify my question. I know the official doc of these scopes, 
that data are broadcasted in GLOBAL and UNIT is maintained as 1-to-1. 
What I'd like to know is when we should use GLOBAL, and when to use 
UNIT? When I deploy multiple units of a charm, does it mean its end of 
relation must use UNIT? if so, what about the provide end, should it be 
UNIT? GLOBAL? SERVICE?


On 06/07/2017 09:22 PM, fengxia wrote:
> Hi Juju,
>
> I'm learning to write a relation. One thing that's puzzling to me is 
> the scope. The question is, must provide and require use the same scope?
>
> For experiment, I have a scope.GLOBAL provide and scope.UNIT require. 
> In deployment, there is one provide unit and three require units. In 
> this setup, I was able to call set_remote() from provide side to pass 
> a dict to require side (get_remote()).
>
> However, if I change provide to be scope.UNIT also, it generated an 
> error:
>
> unit-A-52: 21:15:44 INFO unit.A/52.b-relation-joined ValueError: 
> Conversation with scope 'b/120' not found
>
> Could you elaborate what the behavior should be when these scopes 
> selected on either side?
>
> | provides | requires |
> | GLOBAL   | GLOBAL   |
> | UNIT     | UNIT     |
> | GLOBAL   | UNIT     |
>

-- 
Feng xia
Engineer
Lenovo USA

Phone: 5088011794
fxia1 at lenovo.com
  	
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