Icehouse Design Summit

With multiple location feature Glance support an image has more then one backend storage location, it allow Glance using HA approach to retrieve their content from different backend when download API be required by client, and Glance also allow the image consumer access image from backend storage directly via a particular location if administrator allow glance export location metadata out to client.

Currently every image property are all belong to the image but its particular location, it caused some limitations for such useful use cases. For example, a location could has own status, under it Glance can handle location more efficiently such as 'pending_delete' for a particular location. And if we moving 'disk_format' and 'container_format' ('checksum', 'size' will be involved) properties to location level, then it could help Glance support more useful use cases, that means an image Glance owned could have different disk and/or container format, this will allow client side such as Nova consuming image more free.

I consider this change will help Glance future features' implementation also.

I'd like discuss following with team:
1. Make sure what we want to make on image location level. Which property want to add, which one want to move.
My candidate: status, disk_format, container_format, checksum and size.
2. Image location state transition diagram if we want to do it.
3. The influence for the consuming side. Client side related changing.
4. Implementation discussion.

Etherpad for discussion: https://etherpad.openstack.org/enhancing-glance-image-location-property
A related BP: https://blueprints.launchpad.net/glance/+spec/image-location-status


(Session proposed by Zhi Yan Liu)