Proposal: Repository Image Search by {description, platform}

[ncultra]

With prototype ports of Docker to aarch64, Power LE, and s390 it has become apparent that we need to search and pull images from a repository based (in part) on the architectural platform they are built for.

Today repository search accepts a string which is then used to search the description field for each image. The list of images that hit are returned in a dictionary {'name': name 'description':description}.

The description field can be augmented by a single tag; the custom is to use a tag to indicate a release or build, just as you would use a tag in a source code control system.

Adding an optional platform field to the search term would allow a more precise image search when the native platform is important. There would bee no need to overload the description or tag data for an image. There is no need to alter the return value of repository search.

[duglin]

One of the biggest design points around this would probably be: are two images of the same thing, but for two different platforms, variants of the same "image" or two different images? I think this will influence whether a "platform" type of field is more like a view over shared data, just extra metadata like "description" or part of the unique naming aspect of the image - much like username, name and tag. My current thinking is that they are two independent images - with no relationship. "Platform" is just another search term (like name) but not part of the naming of the image.

In thinking about this it would seem we could do the following:
Docker CLI:

• allow for an optional "platform" parameter to be specified on push, pull, search and tag
• if not specified, the cli will use the current env's value - e.g. what "uname -a" might return
• "docker search" should probably allow for some wildcarding (e.g. -p * to mean any/all)

Registry:

• add a "platform" field as a sibling to "description"
• if absent on push,pull,tag it defaults to current (x86?)
• if absent on search it defaults to all/any
• we probably need to add a new API to allow for people to ask for the list of available "platform" values - see comment below.

Dockerfile/FROM:

• modify the syntax to: FROM [:tag] [platform]
• if not present the current env's value should be used on the resulting pull

Additionally, we should consider whether this field is "free form" or "locked down" by the registry's admin? In order to ensure people don't run into typo/naming/... issues, I think this should be a configurable aspect of the registry, but most people will probably choose to lock it down and therefore we need a config mechanism by which the registry admin can indicate the list of valid values.

Not sure if it should be "platform" or "arch" - but that's a minor point :-)
Anyway, just some initial thoughts for people to throw arrows at.

[stevvooe]

There are few relevant tickets happening in distribution. The first is the new manifest proposal, which will support multi-architecture images: distribution/distribution#62. The other is the ongoing effort to define a scalable search API for the v2 registry system distribution/distribution#206.

[LK4D4]

@stevvooe @dmcgowan is this still an issue?

[dmcgowan]

This feature request is still valid. The search API has not been updated and V2 updates remain in the design phase pending an owner to take it on.