Open Stack

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