fix: support seamless upgrades with pod uid in socket path names + default helm chart values

[alimaazamat]

Fixes issue #107
Socket path names in the format {baseName}{suffix} works fine for legacy deployments but if we have seamless upgrades (max surge 1 maxUnavailable 0) then it doesn't work because the socket path names include uid {baseName}-{uid}{suffix}.
Without UIDs in socket names: Two pods can't run simultaneously because they'd conflict trying to create the same socket file names.

Solution:
Include pod UID in socket paths. Define default seamless upgrade values. Chart now defaults to seamless upgrades (max surge 1 maxUnavailable 0) which users can override by setting kubeletPlugin.updateStrategy.rollingUpdate values directly.

How to test:

# Build the kubelet plugin binary with the changes
make cmd-dra-example-kubeletplugin
# in demo dir and build/load image
cd demo
./scripts/build-driver-image.sh
./scripts/load-driver-image-into-kind.sh
cd ..
# made a new namespace
kubectl create namespace dra-example-driver

# Test Default Config where seamless upgrades disabled
helm install dra-example-driver deployments/helm/dra-example-driver --namespace dra-example-driver
# Check deployment
kubectl get pods --namespace dra-example-driver
# I verified DaemonSet update strategy correctly has **maxSurge: 1, maxUnavailable: 0**
# Check logs for legacy socket paths
kubectl logs -n dra-example-driver $POD_NAME | grep -E "(socket|endpoint)"
 
# Upgrade deployment triggering rolling update to enable seamless upgrades
kubectl patch daemonset dra-example-driver-kubeletplugin -n dra-example-driver \
  -p '{"spec":{"template":{"metadata":{"annotations":{"test-rolling-update":"'$(date +%s)'"}}}}}'
# verify uid socket paths in new pods
NEW_POD_NAME=$(kubectl get pods -n dra-example-driver -o jsonpath='{.items[0].metadata.name}')
kubectl logs -n dra-example-driver $NEW_POD_NAME | grep -E "(socket|endpoint)" | head -5

# Test non-seamless (overriding defaults)
helm upgrade dra-example-driver deployments/helm/dra-example-driver \
  --namespace dra-example-driver \
  --set kubeletPlugin.updateStrategy.rollingUpdate.maxSurge=0 \
  --set kubeletPlugin.updateStrategy.rollingUpdate.maxUnavailable=1

# Verify old rolling update strategy {"maxSurge": 0, "maxUnavailable": 1}
kubectl get daemonset dra-example-driver-kubeletplugin -n dra-example-driver \
  -o jsonpath='{.spec.updateStrategy.rollingUpdate}' | jq .

Results:
Seamless Upgrades Enabled default behavior:
maxSurge: 1, maxUnavailable: 0

I0422 23:21:04.522190 1 health.go:71] "connecting to registration socket" path="unix:///var/lib/kubelet/plugins_registry/gpu.example.com-<POD_UID>-reg.sock"
I0422 23:21:04.522536 1 health.go:89] "connecting to DRA socket" path="unix:///var/lib/kubelet/plugins/gpu.example.com/dra-<POD_UID>.sock"

Seamless Upgrades Disabled by user overriding helm chart:
maxSurge: 0, maxUnavailable: 1

• socket paths still include pod uid

I0422 23:18:56.245888 1 health.go:71] "connecting to registration socket" path="unix:///var/lib/kubelet/plugins_registry/gpu.example.com-<POD_UID>-reg.sock"
I0422 23:18:56.246339 1 health.go:89] "connecting to DRA socket" path="unix:///var/lib/kubelet/plugins/gpu.example.com/dra-<POD_UID>.sock"

[alimaazamat]

/assign

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/lifecycle stale

[nojnhuh]

/remove-lifecycle stale

[k8s-triage-robot]

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/lifecycle stale

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The Kubernetes project currently lacks enough active contributors to adequately respond to all PRs.

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/lifecycle rotten

[nojnhuh]

/remove-lifecycle rotten

[nojnhuh]

/lgtm

Thanks @alimaazamat! Could you please squash down to one commit?

[k8s-ci-robot]

LGTM label has been added.

Details

Git tree hash: f3f1c421dc5b8f7c738ee6c521b0e31781ba3808

[nojnhuh]

/approve

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[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: alimaazamat, nojnhuh

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