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Mathieu,

Thank you for sharing this.  Nice to see you have a solution that looks 
agreeable to Matt.  Do you think you can get a spec pushed up and 
propose your code?

Jay



On 4/3/2017 2:21 PM, Mathieu Gagné wrote:
> On Mon, Apr 3, 2017 at 12:27 PM, Walter Boring <waboring at hemna.com> wrote:
>> Actually, this is incorrect.
>>
>> The sticking point of this all was doing the coordination and initiation of
>> workflow from Nova.   Cinder already has the ability to call the driver to
>> do the resize of the volume.  Cinder just prevents this now, because there
>> is work that has to be done on the attached side to make the new size
>> actually show up.
>>
>> What needs to happen is:
>>   A new Nova API needs to be created to initiate and coordinate this effort.
>> The API would call Cinder to extend the size, then get the connection
>> information from Cinder for that volume, then call os-brick to extend the
>> size, then update the domain xml to tell libvirt to extend the size.   The
>> end user inside the VM would have to issue the same SCSI bus rescan and
>> refresh that happens inside of os-brick, to make the kernel and filesystem
>> in the VM recognize the new size.
>>
>> os-brick does all of the heavy lifting already on the host side of things.
>> The Connector API entry point:
>> https://github.com/openstack/os-brick/blob/master/os_brick/initiator/initiator_connector.py#L153
>>
>> iSCSI example:
>> https://github.com/openstack/os-brick/blob/master/os_brick/initiator/connectors/iscsi.py#L370
>>
>> os-brick's code works for single path and multipath attached volumes.
>> multipath has a bunch of added complexity with resize that should already be
>> taken care of here:
>> https://github.com/openstack/os-brick/blob/master/os_brick/initiator/linuxscsi.py#L375
>>
> I would like to share our private implementation (based on Mitaka):
> https://gist.github.com/mgagne/9402089c11f8c80f6d6cd49f3db76512
>
> The implementation makes it so Cinder leverages the existing Nova
> external-events endpoint to trigger the BDM update and iSCSI rescan on
> the host.
>
> As always, the guest needs to update the partition table/filesystem if
> it wants to benefit from the new free space.
>
> Let me know if this is an implementation you want me to contribute upstream.
>
> --
> Mathieu
>
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