Juju providers should be able to get image id's automagically

[Mark Shuttleworth]

When configuring Juju for the HP public cloud I needed to enter an image-id, like this:

environments:
  hpcloud:
    default-image-id: [8419]
    default-series: precise

We value a "just works" approach, which in part means minimising the amount of information that a user needs to glean, when the system can infer that from things the user will definitely know.

In this case, while it's useful to be able to specify the image-id, it would be better if that were not required, but instead if juju, by policy and online services, could work that out from the "default-series" preference. Providers for different environments will need to map that series preference to the appropriate image automagically, so that users don't need to update that when, for example, a newer base image rolling up fixes is published.

[Clint Byrum (clint-fewbar)]

This was discussed at length at UDS-Q, as part of this blueprint:

https://blueprints.launchpad.net/ubuntu/+spec/servercloud-r-juju-resource-map

It wasn't worked on because of the decision to focus on the Go port, but it is still needed. I've re-targetted it at R and proposed it for UDS-R.

We can use https://cloud-images.ubuntu.com to lookup image IDs on public clouds, but we will also need to offer users the ability to have a local resource map for private clouds. There is also a need to map instance types to their constraints in EC2, since Amazon does not offer this via an API.

[Mark Shuttleworth (sabdfl)]

Sounds good - thanks!

[Kapil Thangavelu (hazmat)]

It would be good to also produce such an index for clouds where we don't publish images, so that juju use is seamless everywhere. I've talked with ben & scott about using query2 for use with non-ec2 images, though its still not ideal, at the moment its focused fairly verbose with extraneous things and embedded build references across multiple files (http://cloud-images.ubuntu.com/query2/server/ec2.json). For openstack servers its possible we can glean some useful information from the glance server (http://docs.openstack.org/developer/glance/glanceapi.html#list-available-images-in-more-detail), but the contents of such are adhoc. At a minimum we need to know its ubuntu and its release series for a given image.