Open Stack

Hi, all
	I'm wondering what's the exact meaning of the "source" in the Counter/Meter and hope to get idea of the original design.
	Currently the source is set by central/compute manager and collector service according to cfg.CONF.counter_source, which is 'openstack' by default now.
	How will such information be utilized? What's the supposed configuration of the counter_source?
	 I checked the API and the storage implementation, and didn't find any hints on how are the source utilized, or why user want to query /v1/sources/(source)/projects or /v1/sources/(source)/meters. 

	IMHO, does it make sense to make the source as part of the counter, and pollster/notification handle decide the value? And instead of configurable, it can be fixed as "nova", "swift" etc. After all, it's counter_source, and should be counter specific.

Thanks
--jyh