Compression parameters ignored

[apgrucza]

The compression algorithm parameters are completely ignored when using buildx to build and push an image. This is despite following the example command in the compression documentation. The size and media type in the manifest remain the same regardless of the compression algorithm I choose.

It appears the compression parameters are not being read at all because if I provide invalid values (e.g. a non-numeric compression-level) I do not get an error.

I have tested on both WSL (Ubuntu) and Windows. The below sequence of commands demonstrates the problem.

BuildKit version

PS C:\Users\usrname> docker buildx ls
NAME/NODE           DRIVER/ENDPOINT     STATUS    BUILDKIT   PLATFORMS
default             docker
 \_ default          \_ default         running   v0.15.2    linux/amd64, linux/amd64/v2, linux/amd64/v3, linux/arm64, linux/riscv64, linux/ppc64le, linux/s390x, linux/386, linux/mips64le, linux/mips64, linux/arm/v7, linux/arm/v6
desktop-linux*      docker
 \_ desktop-linux    \_ desktop-linux   running   v0.15.2    linux/amd64, linux/amd64/v2, linux/amd64/v3, linux/arm64, linux/riscv64, linux/ppc64le, linux/s390x, linux/386, linux/mips64le, linux/mips64, linux/arm/v7, linux/arm/v6

Dockerfile

PS C:\Users\usrname> cat Dockerfile
FROM alpine
ARG ID
RUN cp /bin/busybox /home

Build and push image compressed with gzip

PS C:\Users\usrname> docker buildx build --build-arg ID=gzip --output type=image,name=usrname/dummy:gzip,push=true,compression=gzip .
[+] Building 23.7s (7/7) FINISHED                                                                  docker:desktop-linux
 => [internal] load build definition from Dockerfile                                                               0.0s
 => => transferring dockerfile: 85B                                                                                0.0s
 => [internal] load metadata for docker.io/library/alpine:latest                                                   0.0s
 => [internal] load .dockerignore                                                                                  0.0s
 => => transferring context: 2B                                                                                    0.0s
 => CACHED [1/2] FROM docker.io/library/alpine:latest                                                              0.0s
 => [2/2] RUN cp /bin/busybox /home                                                                                0.3s
 => exporting to image                                                                                             0.0s
 => => exporting layers                                                                                            0.0s
 => => writing image sha256:2d1df90518de65637f7798eed87f30ad75a547e0e6d30d6acc5b5547731afc3e                       0.0s
 => => naming to docker.io/usrname/dummy:gzip                                                                      0.0s
 => pushing usrname/dummy:gzip with docker                                                                        17.3s
 => => pushing layer e2696caccd8d                                                                                  7.9s
 => => pushing layer 94e5f06ff8e3                                                                                 15.6s

Build and push image compressed with zstd

PS C:\Users\usrname> docker buildx build --build-arg ID=zstd --output type=image,name=usrname/dummy:zstd,push=true,compression=zstd .
[+] Building 23.0s (7/7) FINISHED                                                                  docker:desktop-linux
 => [internal] load build definition from Dockerfile                                                               0.0s
 => => transferring dockerfile: 85B                                                                                0.0s
 => [internal] load metadata for docker.io/library/alpine:latest                                                   0.0s
 => [internal] load .dockerignore                                                                                  0.0s
 => => transferring context: 2B                                                                                    0.0s
 => CACHED [1/2] FROM docker.io/library/alpine:latest                                                              0.0s
 => [2/2] RUN cp /bin/busybox /home                                                                                0.2s
 => exporting to image                                                                                             0.0s
 => => exporting layers                                                                                            0.0s
 => => writing image sha256:e211987a585928034e89c408c7cdc6f15a77a2e6b45b4616cec10f0e5dfab665                       0.0s
 => => naming to docker.io/usrname/dummy:zstd                                                                      0.0s
 => pushing usrname/dummy:zstd with docker                                                                        17.0s
 => => pushing layer 7b5d89f5975c                                                                                  7.7s
 => => pushing layer 94e5f06ff8e3                                                                                 15.8s

Build and push uncompressed image

PS C:\Users\usrname> docker buildx build --build-arg ID=uncompressed --output type=image,name=usrname/dummy:uncompressed,push=true,compression=uncompressed .
[+] Building 23.4s (7/7) FINISHED                                                                  docker:desktop-linux
 => [internal] load build definition from Dockerfile                                                               0.0s
 => => transferring dockerfile: 85B                                                                                0.0s
 => [internal] load metadata for docker.io/library/alpine:latest                                                   0.0s
 => [internal] load .dockerignore                                                                                  0.0s
 => => transferring context: 2B                                                                                    0.0s
 => CACHED [1/2] FROM docker.io/library/alpine:latest                                                              0.0s
 => [2/2] RUN cp /bin/busybox /home                                                                                0.2s
 => exporting to image                                                                                             0.0s
 => => exporting layers                                                                                            0.0s
 => => writing image sha256:d8e8715782f9d17423d267590c2ac74dda8743621a5910a067ffdf3073fde711                       0.0s
 => => naming to docker.io/usrname/dummy:uncompressed                                                              0.0s
 => pushing usrname/dummy:uncompressed with docker                                                                17.1s
 => => pushing layer b2ffd68f6199                                                                                  7.9s
 => => pushing layer 94e5f06ff8e3                                                                                 15.8s

Manifest for gzip image

PS C:\Users\usrname> docker manifest inspect usrname/dummy:gzip
{
        "schemaVersion": 2,
        "mediaType": "application/vnd.docker.distribution.manifest.v2+json",
        "config": {
                "mediaType": "application/vnd.docker.container.image.v1+json",
                "size": 939,
                "digest": "sha256:2d1df90518de65637f7798eed87f30ad75a547e0e6d30d6acc5b5547731afc3e"
        },
        "layers": [
                {
                        "mediaType": "application/vnd.docker.image.rootfs.diff.tar.gzip",
                        "size": 3623844,
                        "digest": "sha256:ec99f8b99825a742d50fb3ce173d291378a46ab54b8ef7dd75e5654e2a296e99"
                },
                {
                        "mediaType": "application/vnd.docker.image.rootfs.diff.tar.gzip",
                        "size": 513591,
                        "digest": "sha256:958ef0a9c069b82a13223ae4be9b6bfaeebdfa4070dc7045135b3c1db199da1a"
                }
        ]
}

Manifest for zstd image

PS C:\Users\usrname> docker manifest inspect usrname/dummy:zstd
{
        "schemaVersion": 2,
        "mediaType": "application/vnd.docker.distribution.manifest.v2+json",
        "config": {
                "mediaType": "application/vnd.docker.container.image.v1+json",
                "size": 939,
                "digest": "sha256:e211987a585928034e89c408c7cdc6f15a77a2e6b45b4616cec10f0e5dfab665"
        },
        "layers": [
                {
                        "mediaType": "application/vnd.docker.image.rootfs.diff.tar.gzip",
                        "size": 3623844,
                        "digest": "sha256:ec99f8b99825a742d50fb3ce173d291378a46ab54b8ef7dd75e5654e2a296e99"
                },
                {
                        "mediaType": "application/vnd.docker.image.rootfs.diff.tar.gzip",
                        "size": 513590,
                        "digest": "sha256:d3792e8213e6ac1b7362242f6d4ca227bafa11bb3ad1836d86e483c46fb7d137"
                }
        ]
}

Manifest for uncompressed image

PS C:\Users\usrname> docker manifest inspect usrname/dummy:uncompressed
{
        "schemaVersion": 2,
        "mediaType": "application/vnd.docker.distribution.manifest.v2+json",
        "config": {
                "mediaType": "application/vnd.docker.container.image.v1+json",
                "size": 955,
                "digest": "sha256:d8e8715782f9d17423d267590c2ac74dda8743621a5910a067ffdf3073fde711"
        },
        "layers": [
                {
                        "mediaType": "application/vnd.docker.image.rootfs.diff.tar.gzip",
                        "size": 3623844,
                        "digest": "sha256:ec99f8b99825a742d50fb3ce173d291378a46ab54b8ef7dd75e5654e2a296e99"
                },
                {
                        "mediaType": "application/vnd.docker.image.rootfs.diff.tar.gzip",
                        "size": 513589,
                        "digest": "sha256:4b50faf70afcaad978d835f74ac88d589952c2e9e2e9454ed84db9c3c2ca7b65"
                }
        ]
}

[tonistiigi]

Setting compression options requires container builder or docker instance with containerd storage. https://docs.docker.com/desktop/containerd/ . Pre-containerd the layer blobs are not created during build but when running docker push.

If the build references a blob that already exists, eg. from a base image or via existing build cache then you need to set force-compression if you wish to reencode the existing blobs.