Enable parallel image pulls

As of 1.27, Kubernetes added support for parallelizing image pulls but
this is not enabled by default.  This is especially useful in situations
where multiple images need to be downloaded to a host, but one of them
is particularly large.

charts/cluster-api-cluster-openstack/templates/control-plane.yaml

@@ -22,6 +22,7 @@ spec:
         name: {{ "'{{ local_hostname }}'" }}
         kubeletExtraArgs:
           cloud-provider: external
+          serialize-image-pulls: "true"
           node-labels: {{- include "openstack.nodelabels.control-plane" . | nindent 12 }}
         taints:
           {{- include "openstack.taints.control-plane" . | nindent 8 }}
@@ -34,6 +35,7 @@ spec:
         name: {{ "'{{ local_hostname }}'" }}
         kubeletExtraArgs:
           cloud-provider: external
+          serialize-image-pulls: "true"
           node-labels: {{- include "openstack.nodelabels.control-plane" . | nindent 12 }}
         taints:
           {{- include "openstack.taints.control-plane" . | nindent 8 }}

charts/cluster-api-cluster-openstack/templates/workload.yaml

@@ -107,6 +107,15 @@ spec:
         path: {{ $file.path }}
         permissions: "0600"
       {{- end }}
+      {{- with $config := $pool.kubelet -}}
+      {{ $_ := set $config "apiVersion" "kubelet.config.k8s.io/v1beta1" -}}
+      {{ $_ := set $config "kind" "KubeletConfiguration" }}
+      - path: /etc/kubernetes/patches/kubeletconfiguration0+strategic.json
+        owner: "root:root"
+        permissions: "0644"
+        content: |
+          {{ $config | toJson }}
+      {{- end }}
       joinConfiguration:
         nodeRegistration:
           name: {{ "'{{ local_hostname }}'" }}
@@ -115,4 +124,8 @@ spec:
             node-labels: {{- include "openstack.nodelabels.workload" $context | nindent 14 }}
           taints:
             {{- include "openstack.taints.workload" $ | nindent 10 }}
+        {{- if $pool.kubelet }}
+        patches:
+          directory: /etc/kubernetes/patches
+        {{- end }}
 {{- end }}

charts/cluster-api-cluster-openstack/values.yaml

@@ -138,6 +138,11 @@ controlPlane:
 #    - path: /etc/cat
 #      content: bWVvdw==
 #
+#    # Additional configuration to be passed to the kubelet can be specifed here
+#    kubelet:
+#      # For example:
+#      serializeImagePulls: "false"
+#
 #    # Enable or disable cluster autoscaling.
 #    # This object is considered immutable.
 #    autoscaling: