Post Build Step hanging since v6.17.0 with kubernetes driver

[jamesoneill997]

Contributing guidelines

• I've read the contributing guidelines and wholeheartedly agree

I've found a bug, and:

• The documentation does not mention anything about my problem
• There are no open or closed issues that are related to my problem

Description

Since the buildx history export change introduced in 6.17.0, the post build phase hangs every time. Setting to legacy build with DOCKER_BUILD_EXPORT_LEGACY or downgrading to <6.17.0 fixes the problem.

Expected behaviour

Post build step should complete relatively quickly.

Actual behaviour

Post build step hangs indefinitely.

Post job cleanup.
Post job cleanup.
Generating build summary
  exporting build record to /home/runner/_work/_temp/docker-actions-toolkit-d5qy7V/export
  Post job cleanup.

Repository URL

No response

Workflow run URL

No response

YAML workflow

- uses: actions/checkout@v4
      if: ${{ !inputs.skip_checkout }}
      with:
        fetch-depth: 0

    - uses: docker/setup-buildx-action@v3
      with:
        driver: kubernetes


    - name: Build and push image
      uses: docker/build-push-action@v6.18.0
      with:
        context: .
        build-args: ${{ inputs.build_args }}
        file: ${{ inputs.dockerfile_path }}
        cache-from: type=gha,scope=${{ github.ref_name }}
        cache-to: type=gha,mode=max,scope=${{ github.ref_name }}
        push: true
        secret-files:[REDACTED]
        tags: ${{ env.TAGS }}
        platforms: ${{ inputs.platforms }}
      # env: uncommenting this stops post build from hanging
        # DOCKER_BUILD_EXPORT_LEGACY: true

Workflow logs

Post job cleanup.
Post job cleanup.
Generating build summary
  exporting build record to /home/runner/_work/_temp/docker-actions-toolkit-d5qy7V/export
  Post job cleanup.

Hangs here. We did see one run where the buildx history export was the last command and seemed to be hanging, this would make sense when we take into account the fact that legacy works and <6.17 works also.

BuildKit logs

Additional info

No response

[crazy-max]

driver: kubernetes

Maybe an issue with the kubernetes driver, is your repo public so we can take a look at the logs?

[jamesoneill997]

The repo is not public I'm afraid, sorry :(

Let me know if there's anything else that I can provide

[abatilo]

If you disable the summary generation, things seem fine again. I've experienced this on a Kubernetes driver agent also

[crazy-max]

If you disable the summary generation, things seem fine again. I've experienced this on a Kubernetes driver agent also

Yes this seems to be similar to docker/setup-buildx-action#270, I will add a check in the actions to skip summary generation for kubernetes driver in the meantime.

@abatilo Do you have a workflow run I can check please so we can fix it on Buildx side?

Also does it work if you use the legacy exporter?:

env:
  DOCKER_BUILD_EXPORT_LEGACY: true

[vvanouytsel]

We are also hitting the same issue and we are also using the kubernetes driver.

Setting up the builders using buildkit and kubernetes driver:

- name: Set up buildkit builders
  id: builder
  uses: docker/setup-buildx-action@e468171a9de216ec08956ac3ada2f0791b6bd435 #v3.11.1
  with:
    driver: kubernetes
    platforms: linux/amd64
    driver-opts: |
      namespace=${{ inputs.buildenv_namespace }}
      nodeselector=kubernetes.io/arch=amd64
    append: |
      - platforms: linux/arm64
        driver-opts:
          - namespace=${{ inputs.buildenv_namespace }}
          - nodeselector=kubernetes.io/arch=arm64

Finally build the image:

- name: Build and optionally push image
  uses: docker/build-push-action@263435318d21b8e681c14492fe198d362a7d2c83 #v6.18.0
  with:
    builder: ${{ steps.builder.outputs.name}}
    context: ${{ inputs.context }}
    platforms: linux/amd64,linux/arm64
    cache-from: type=azblob,name=${{ github.event.repository.name }},account_url=${{ inputs.cache_url }},secret_access_key=${{ secrets.CACHE_ACCESS_KEY }}
    cache-to: "type=azblob,name=${{ github.event.repository.name  }},account_url=${{ inputs.cache_url }},secret_access_key=${{ secrets.CACHE_ACCESS_KEY }},mode=max"
    push: ${{ inputs.push }}
    file: ${{ inputs.dockerfile }}
    tags: ${{ steps.meta.outputs.tags }}
  env:
    DOCKER_BUILD_EXPORT_LEGACY: true # https://github.com/docker/build-push-action/issues/1388

When using DOCKER_BUILD_EXPORT_LEGACY, the post job cleanup continues and does not hang.
But a warning is shown, as we have no docker daemon running. Which is expected as we are running with the kubernetes driver.

Post job cleanup. 
Generating build summary 
 exporting build record to /home/runner/_work/_temp/docker-actions-toolkit-06Qu9d/export 
 Warning: Docker daemon needs to be running to export a build record

[crazy-max]

When using DOCKER_BUILD_EXPORT_LEGACY, the post job cleanup continues and does not hang. But a warning is shown, as we have no docker daemon running. Which is expected as we are running with the kubernetes driver.

Post job cleanup. 
Generating build summary 
 exporting build record to /home/runner/_work/_temp/docker-actions-toolkit-06Qu9d/export 
 Warning: Docker daemon needs to be running to export a build record

Ah thanks, yes that makes sense as the legacy build export uses docker run and therefore needs the docker engine.

[crazy-max]

I made some tests by creating a k3d cluster and building with it and exporting seems to work fine:

$ docker buildx create   --name=kube   --driver=kubernetes --driver-opt=namespace=buildkit
kube
$ docker buildx inspect kube --bootstrap
#1 [internal] booting buildkit
#1 waiting for 1 pods to be ready, timeout: 2 minutes
#1 waiting for 1 pods to be ready, timeout: 2 minutes 6.6s done
#1 DONE 6.6s
Name:          kube
Driver:        kubernetes
Last Activity: 2025-07-29 14:38:37 +0000 UTC

Nodes:
Name:                  kube0
Endpoint:              kubernetes:///kube?deployment=buildkit-b9b92c4e-1316-4c72-b2af-97601d417627-3bdfd&kubeconfig=%2Fhome%2Fcrazy%2Fk3s.yaml
Driver Options:        namespace="buildkit"
Status:                running
BuildKit daemon flags: --allow-insecure-entitlement=network.host
BuildKit version:      v0.22.0
Platforms:             linux/amd64, linux/amd64/v2, linux/amd64/v3, linux/arm64, linux/riscv64, linux/ppc64le, linux/s390x, linux/386, linux/arm/v7, linux/arm/v6
Labels:
 org.mobyproject.buildkit.worker.executor:         oci
 org.mobyproject.buildkit.worker.hostname:         kube0-69d8dc8669-ghcjg
 org.mobyproject.buildkit.worker.network:          host
 org.mobyproject.buildkit.worker.oci.process-mode: sandbox
 org.mobyproject.buildkit.worker.selinux.enabled:  false
 org.mobyproject.buildkit.worker.snapshotter:      overlayfs
GC Policy rule#0:
 All:            false
 Filters:        type==source.local,type==exec.cachemount,type==source.git.checkout
 Keep Duration:  48h0m0s
 Max Used Space: 488.3MiB
GC Policy rule#1:
 All:            false
 Keep Duration:  1440h0m0s
 Reserved Space: 9.313GiB
 Max Used Space: 93.13GiB
 Min Free Space: 188.1GiB
GC Policy rule#2:
 All:            false
 Reserved Space: 9.313GiB
 Max Used Space: 93.13GiB
 Min Free Space: 188.1GiB
GC Policy rule#3:
 All:            true
 Reserved Space: 9.313GiB
 Max Used Space: 93.13GiB
 Min Free Space: 188.1GiB

Building with this builder and checking the record in the history:

$ docker buildx --builder kube history ls
BUILD ID                    NAME      STATUS      CREATED AT           DURATION   
qdwd758xqnhw7oh3rl2ylcy2a   buildx    Completed   About a minute ago   1m  9s     Open

Then exporting:

$ docker buildx --builder kube history export qdwd758xqnhw7oh3rl2ylcy2a > k3d.dockerbuild
$ ls k3d.dockerbuild
k3d.dockerbuild

Importing it back in Docker Desktop:

$ docker buildx --builder kube history import --file k3d.dockerbuild
docker-desktop://dashboard/build/.imported/_/qdwd758xqnhw7oh3rl2ylcy2a

It works fine and opens the Builds view:

So this might be something else.

If someone can show where it hangs that would helpful 🙏