[openstack-dev] [nova][cinder] volumes stuck detaching attaching and force detach

John Garbutt john at johngarbutt.com
Tue Feb 23 18:04:49 UTC 2016

On 22 February 2016 at 22:08, Walter A. Boring IV <walter.boring at hpe.com> wrote:
> On 02/22/2016 11:24 AM, John Garbutt wrote:
>> Hi,
>> Just came up on IRC, when nova-compute gets killed half way through a
>> volume attach (i.e. no graceful shutdown), things get stuck in a bad
>> state, like volumes stuck in the attaching state.
>> This looks like a new addition to this conversation:
>> http://lists.openstack.org/pipermail/openstack-dev/2015-December/082683.html
>> And brings us back to this discussion:
>> https://blueprints.launchpad.net/nova/+spec/add-force-detach-to-nova
>> What if we move our attention towards automatically recovering from
>> the above issue? I am wondering if we can look at making our usually
>> recovery code deal with the above situation:
>> https://github.com/openstack/nova/blob/834b5a9e3a4f8c6ee2e3387845fc24c79f4bf615/nova/compute/manager.py#L934
>> Did we get the Cinder APIs in place that enable the force-detach? I
>> think we did and it was this one?
>> https://blueprints.launchpad.net/python-cinderclient/+spec/nova-force-detach-needs-cinderclient-api
>> I think diablo_rojo might be able to help dig for any bugs we have
>> related to this. I just wanted to get this idea out there before I
>> head out.
>> Thanks,
>> John
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>> .
> The problem is a little more complicated.
> In order for cinder backends to be able to do a force detach correctly, the
> Cinder driver needs to have the correct 'connector' dictionary passed in to
> terminate_connection.  That connector dictionary is the collection of
> initiator side information which is gleaned here:
> https://github.com/openstack/os-brick/blob/master/os_brick/initiator/connector.py#L99-L144
> The plan was to save that connector information in the Cinder
> volume_attachment table.  When a force detach is called, Cinder has the
> existing connector saved if Nova doesn't have it.  The problem was live
> migration.  When you migrate to the destination n-cpu host, the connector
> that Cinder had is now out of date.  There is no API in Cinder today to
> allow updating an existing attachment.
> So, the plan at the Mitaka summit was to add this new API, but it required
> microversions to land, which we still don't have in Cinder's API today.

Ah, OK.

We do keep looping back to that core issue.


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