[openstack-dev] inconsistent naming? node vs host vs vs hypervisor_hostname vs OS-EXT-SRV-ATTR:host

Jiang, Yunhong yunhong.jiang at intel.com
Sat Mar 1 05:53:52 UTC 2014


> -----Original Message-----
> From: Chris Friesen [mailto:chris.friesen at windriver.com]
> Sent: Friday, February 28, 2014 10:07 AM
> To: openstack-dev at lists.openstack.org
> Subject: Re: [openstack-dev] inconsistent naming? node vs host vs vs
> hypervisor_hostname vs OS-EXT-SRV-ATTR:host
> 
> On 02/28/2014 11:38 AM, Jiang, Yunhong wrote:
> > One reason of the confusion is, in some virt driver (maybe xenapi or
> > vmwareapi), one compute service manages multiple node.
> 
> Okay, so in the scenario above, is the nova-compute service running on a

I think the nova compute service runs on a host, as you can see from compute/manager.py and manager.py. 

> "node" or a "host"?  (And if it's a "host", then what is the "compute
> node"?)

Check the update_available_resource() at compute/manager.py for the node idea.

> 
> What is the distinction between "OS-EXT-SRV-ATTR:host" and
> "OS-EXT-SRV-ATTR:hypervisor_hostname" in the above case?

According to _extend_server() at ./api/openstack/compute/contrib/extended_server_attributes.py, the "OS-EXT-SRV-ATTR:hypervisor_hostname is the node and the  "OS-EXT-SRV-ATTR:host" is the host.

I agree this is a bit confusing, especially the document is not clearly, I'd call the " OS-EXT-SRV-ATTR:hypervisor_hostname" as 
" OS-EXT-SRV-ATTR:hypervisor_nodename", which makes more sense and more clearly. Per my understanding with the xenapi, there is a hypervisor on each compute node, and XenAPI (or any name for that software layer) manage multiple (or 1 in extreme case) nodes, that XenAPI software layer interact with nova service and is like a host from nova point of view.

Dan has some interesting discussion on the Nova meet up on this and the cell (so called cloud NUMA IIRC?)

Thanks
--jyh

> 
> Chris
> 
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