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On 4/16/2017 10:35 PM, Alex Xu wrote:
> Is it strange that the 'nova service-list' and 'nova host-list' return
> the hosts which didn't have host mapping yet?

It's kind of strange yes. We could probably make GET /os-hypervisors 
work without requiring the host mappings, but it just doesn't today 
because of some targeted calls within each cell to fill the response.

So we could probably decouple things a bit internally in the API if we 
wanted to do this differently and not require a host mapping, but for 
now I knew we could get the same results by just using os-services and 
get Kolla unblocked (this came up Friday morning last week so I was 
rushing for a solution).

>
> How the user to know whether a host was added to a cell or not?

A user doesn't need to know, but an operator would care. This actually 
came up in IRC last week [1] when Kevin Fox was asking similar 
questions, and I have a TODO to write some FAQs for cells v2.

We talked about how the "nova-manage cell_v2 discover_hosts" command is 
idempotent and if there are new unmapped hosts you could just run it and 
pick them up - the trick is knowing when to run it, unless you configure 
the scheduler to use "discover_hosts_in_cells_interval" for auto-discovery.

We also talked about the option of building on the "nova-manage cell_v2 
list_cells" command to also optionally dumping hosts per cell, or just 
run the "nova-manage host list" command pointed at your cell config.

At some point we might want to consider returning cell uuid out of the 
os-services API when listing services or hosts, something like that.

[1] 
http://eavesdrop.openstack.org/irclogs/%23openstack-nova/%23openstack-nova.2017-04-10.log.html#t2017-04-10T20:25:47

-- 

Thanks,

Matt