Give access to Image ID

[remmeier]

Docker v1.10 introduced a content/digest-based image ID to uniquely identify docker images. It would be great if this image ID would be available from the gradle (and maybe maven) plugin after the image has been built or is deemed being already up-to-date.

Having the image ID would, for example, let the subsequent deployment processes skip containers that do not change (without having to resolve tags to image ids or workaround with manual mechanisms). This is of particular importance for larger multi-project gradle setups / single repository approaches where a single build manages multiple images.

[coollog]

Hi @remmeier , after some discussions over how to provide the user with the digest output, we are planning to have the Jib tasks/goals output a jib-image.digest into the build output directory (build/jib-image.digest for Gradle/target/jib-image.digest for Maven). This file will contain the container image digest. Will this be adequate for your use case?

[remmeier]

yes thx, that would be a great help.

[briandealwis]

Just so I'm clear @coollog, you are proposing we write out the manifest digest (type application/vnd.docker.distribution.manifest.v2+json, not the container configuration digest (type application/vnd.docker.container.image.v1+json)?

(docker images --digests reports the container configuration digests as the Image ID, and the manifest digest as Digest. The manifest references the container configuration as config.digest.)

[coollog]

Yes, the manifest digest, which is the digest portion of the image reference if it's qualified with a digest (ie. gcr.io/distroless/java@sha256:bb1c9179c2263733f235291998cb849d52fb730743125420cf4f97a362d6a6dd where sha256:bb1c9179c2263733f235291998cb849d52fb730743125420cf4f97a362d6a6dd is the image digest.

[coollog]

Hmm, maybe we should write out jib-image.id as well. @remmeier Do you happen to need the Docker Image ID (config digest) or is the image digest enough?

[remmeier]

thx a lot! I'm ok with either. i could imagine that some people may expect the docker image id as it is well establusged

[coollog]

Filed #1204 for that!

[coollog]

Hi @remmeier , @sdavids, @novotnyr, @keykey7, @Tanmayshetty, version 0.10.0 has been released with the image digest written out to a jib-image.digest file in the build output directory.