fix(docker): remove broken symlink creation for varnish exporter

[CorentinRegnier]

Summary

This pull request fixes a runtime issue in the GoReleaser.Dockerfile that affects the prometheus_varnish_exporter binary. While the image builds successfully, the exporter fails to run due to an invalid symlink.

Problem

The Dockerfile attempts to create a symlink to prometheus_varnish_exporter after extracting the archive:

ln -sf /exporter/prometheus_varnish_exporter-<version>/prometheus_varnish_exporter prometheus_varnish_exporter

However, this symlink points to a path that no longer exists at runtime, because the extracted directory is not preserved or included properly in the final image layer. As a result, the binary at /exporter/prometheus_varnish_exporter is broken.

This causes container startup to fail when the exporter is invoked.

Screenshot / Error output

Click to expand runtime error

❯ docker run --rm -it --entrypoint="" quay.io/mittwald/kube-httpcache:v0.9.1 bash
root@80cb0973941c:/# ls -al /exporter/
total 32
drwxr-xr-x 1 varnish root 4096 Jul 15 13:12 .
drwxr-xr-x 1 root    root 4096 Aug  4 09:46 ..
-rw-r--r-- 1    1001  118 5464 Jul 15 12:55 CHANGELOG.md
-rw-r--r-- 1    1001  118 1078 Jul 15 12:55 LICENSE
-rw-r--r-- 1    1001  118 5705 Jul 15 12:55 README.md
lrwxrwxrwx 1 root    root   84 Jul 15 13:12 prometheus_varnish_exporter -> /exporter/prometheus_varnish_exporter-v1.7.0.linux-amd64/prometheus_varnish_exporter
root@80cb0973941c:/# ls ^C
root@80cb0973941c:/# /exporter/prometheus_varnish_exporter
bash: /exporter/prometheus_varnish_exporter: No such file or directory
root@80cb0973941c:/# /exporter/prometheus_varnish_exporter-v1.7.0.linux-amd64/prometheus_varnish_exporter
bash: /exporter/prometheus_varnish_exporter-v1.7.0.linux-amd64/prometheus_varnish_exporter: No such file or directory
root@80cb0973941c:/# ls -al /tmp/
total 3404
drwxrwxrwt 1 root    root       4096 Jul 15 13:12 .
drwxr-xr-x 1 root    root       4096 Aug  4 09:46 ..
-rw------- 1 varnish varnish 3474239 Jul 15 12:58 prometheus_varnish_exporter-v1.7.0.linux-amd64.tar.gz
root@80cb0973941c:/#

On kubernetes Error: failed to create containerd task: failed to create shim task: OCI runtime create failed: runc create failed: unable to start container process: exec: "/exporter/prometheus_varnish_exporter": stat /exporter/prometheus_varnish_exporter: no such file or directory: unknown

Regression context

This issue was introduced starting from version v0.9.1, when the Prometheus exporter was switched to prometheus_varnish_exporter. The problem is still present on the current master branch.

As of these versions, the image includes a broken symlink for the exporter binary, making the container unusable in runtime contexts like AKS or Helm-based deployments.

What changed

• Removed the unnecessary and broken ln -sf step
• Deleted the archive after extraction for cleanliness

The binary is already placed in the expected location during extraction, so no symlink is required.

How I tested

I built the Docker image with the fix and pushed it to my own container registry:

docker build -t my-registry.example.com/kube-httpcache:dev -f build/package/docker/GoReleaser.Dockerfile .
docker push my-registry.example.com/kube-httpcache:dev

I then deployed it on a real Kubernetes cluster (AKS) by updating the image reference in the Helm values to point to my custom image.

✅ With this fix, the prometheus_varnish_exporter binary runs correctly and the pod starts successfully.
❌ Without the fix, the exporter binary fails to execute due to a broken symlink, preventing proper startup.

Why it matters

Without this fix, the Docker image produces a broken runtime due to a missing binary, even though the build succeeds. This breaks local testing and deployment workflows — particularly those relying on KinD or Helm installs using the built image.