On 10/16/2014 7:26 PM, Christopher Aedo wrote:
On Tue, Sep 9, 2014 at 2:19 PM, Mike Scherbakov
<mscherba...@mirantis.com> wrote:
On Tue, Sep 9, 2014 at 6:02 PM, Clint Byrum <cl...@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


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