Open Stack

On 10/16/2014 7:26 PM, Christopher Aedo wrote:
> On Tue, Sep 9, 2014 at 2:19 PM, Mike Scherbakov
> <mscherbakov at mirantis.com> wrote:
>>> On Tue, Sep 9, 2014 at 6:02 PM, Clint Byrum <clint at fewbar.com> wrote:
>> The idea is not simply deny or hang requests from clients, but provide them
>> "we are in maintenance mode, retry in X seconds"
>>
>>> You probably would want 'nova host-servers-migrate <host>'
>> yeah for migrations - but as far as I understand, it doesn't help with
>> disabling this host in scheduler - there is can be a chance that some
>> workloads will be scheduled to the host.
>
> Regarding putting a compute host in maintenance mode using "nova
> host-update --maintenance enable", it looks like the blueprint and
> associated commits were abandoned a year and a half ago:
> https://blueprints.launchpad.net/nova/+spec/host-maintenance
>
> It seems that "nova service-disable <host> nova-compute" effectively
> prevents the scheduler from trying to send new work there.  Is this
> the best approach to use right now if you want to pull a compute host
> out of an environment before migrating VMs off?
>
> I agree with Tim and Mike that having something respond "down for
> maintenance" rather than ignore or hang would be really valuable.  But
> it also looks like that hasn't gotten much traction in the past -
> anyone feel like they'd be in support of reviving the notion of
> "maintenance mode"?
>
> -Christopher
>
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>

host-maintenance-mode is definitely a thing in nova compute via the 
os-hosts API extension and the --maintenance parameter, the compute 
manager code is here [1].  The thing is the only in-tree virt driver 
that implements it is xenapi, and I believe when you put the host in 
maintenance mode it's supposed to automatically evacuate the instances 
to some other host, but you can't target the other host or tell the 
driver, from the API, which instances you want to evacuate, e.g. all, 
none, running only, etc.

[1] 
http://git.openstack.org/cgit/openstack/nova/tree/nova/compute/manager.py?id=2014.2#n3990

-- 

Thanks,

Matt Riedemann