Support for docker_image.image_id

[evanfarrar]

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Description

docker_image.latest is deprecated, but this is the only property that returns the image ID. I agree that .latest is confusing, not just here but also confusing in certain OCI registries where latest is just a manually updated tag like tags in git, not an auto-computed value like HEAD is in git.

The deprecation notice suggests you use repo_digest instead, which does consistently result in the correct image deploying, but because when the state is refreshed the docker_container.image is recomputed to be the image ID it results in recreating your containers on every terraform apply. However, if this is set to the image ID of the image the container will correctly create itself only once.

I suggest that we rename docker_image.latest to docker_image.image_id (duplicating this functionality during a deprecation period). I'm comfortable adding this feature myself but would prefer indication that it would be accepted by maintainers first.

To add further possible confusion: there is already the docker_image.id, which concatenates the docker image ID with the image repo+name, and this is used internally by terraform for resource identification so it probably has a good reason for being this way. Probably if the .id didn't include this string, we would get strange behaviour if a user defined two docker images with different tags that happened to collide on the same value (imagine a trying to deploy two environments with a dev tag and a stable tag which are usually different but are the same after a major release)

New or Affected Resource(s)

• docker_image
• data.docker_image

Potential Terraform Configuration

data "docker_registry_image" "archivebox" {
  name = "archivebox/archivebox:latest"
}
resource "docker_image" "archivebox" {
  name          = data.docker_registry_image.archivebox.name
  pull_triggers = [data.docker_registry_image.archivebox.sha256_digest]
}               
resource "docker_container" "archive" {
  image = docker_image.archivebox.latest
  name = "archive"
}

References

• n/a