This repo provides a minimum working example for an issue spotted with buildkit's inline caching in versions >=0.8.0, see moby/buildkit#2551

Running

NB

• Requires docker with buildx installed.
• Will remove some images/containers from your local docker (those with names it uses, e.g. registry)

Run:

./test.sh <buildkit_version>

And the script will:

• (cleanup from any previous half-finished run)
• create a new buildx builder using buildkit with the specified version
• boot up a local docker registry
• build the image described in the dockerfile, using inline caching
• run a docker history command
• push the image to the local registry
• rerun the build, using cache-from based on the local registry image we just pushed
• run a docker history command
• (cleanup containers/images)

If you use buildkit version 0.7.0 the two history outputs will be identical as expected. However, if you use a version >= 0.8.0 the second history command will seemingly be offset - it will report the "WORKDIR" command created a layer which is 10kB- and the subsequent command, which downloads a 10kB file, will create a layer which is 0kB in size.