Issue identified with Docker 26 and self-hosted runner.

[#1]

Hi Everyone.

We have become aware of an issue with a recently released version of Docker that is causing issues for some customers utilising the self-hosted runner. The problem manifests itself when trying to run a step that uses a custom Docker-in-Docker image.

Docker have released a new version of the docker engine (https://docs.docker.com/engine/release-notes/26.0/) which is not currently compatible with the runner.

When encountered, the following error will appear in the runner log:

An error occurred whilst inspecting image.
java.lang.NullPointerException: The mapper function returned a null value.

We have been able to reproduce this issue internally and confirm that it is limited to Docker 26. We are investigating the cause of this issue and working on implementing support for it to ensure customers can upgrade.

Please avoid upgrading to Docker v26 until this incompatibility has been resolved. If you are experiencing this issue today, pinning your Docker version to 25.x or an earlier compatible version should remediate the issue.

[Storm Muller]

We've tried setting 

services:
    docker:
      - image: docker:dind

to 

services:
    docker:
      - image: docker:25-dind

In our pipelines file, but the issue remains. 

Do we need to change something on the runners themselves?

[Storm Muller]

Also, please can you update the status page https://bitbucket.status.atlassian.com/ 

[Alex Figliolia]

Storm, you have to downgrade Docker, not dind. If you run docker --version on the runner's host it should return version 25. 

[Storm Muller]

Thanks Alex, I was hoping I wouldn't have to get into the runners themselves, but I appreciate the feedback.

[Storm Muller]

If we're using k8 and the `docker-public.packages.atlassian.com/sox/atlassian/bitbucket-pipelines-runner` image. How can we set the version of docker? Is there a tag we can use?

[Karthik Ashokan]

We have a fleet of Kubernetes auto-scaling runners running in AWS EKS on Kubernetes version 1.28. The container runtime here is containerd version 1.7.2 and is throwing the same null value error. Is this related to the same Docker v26 incompatibility? In our pipelines, we are using Docker 23

definitions:
  services:
    docker-custom:
      type: docker
      image: docker:23

edit: related to the previous comment by Storm

[Storm Muller]

.

[Graham Gatus]

This issue has been resolved in runner version 1.565.