Add rolling update strategy to multi-replica pods (#4267)

This introduces a rolling update strategy to Linkerd deployments that have
three replicas during HA deployments. This allows for at most one pod to begin
terminating before a new pod ready is ready.

This allows for upgrades to take place on three node clusters. As a pod begins
terminating, it opens up the node for the new pod to start initializing.

`.Values.enablePodAntiAffinity` was chosen as the conditional here because it
is set by the `values-ha.yaml` config on HA deployments

charts/linkerd2/templates/controller.yaml

@@ -45,6 +45,11 @@ spec:
       {{.Values.global.controllerComponentLabel}}: controller
       {{.Values.global.controllerNamespaceLabel}}: {{.Values.global.namespace}}
       {{- include "partials.proxy.labels" .Values.global.proxy | nindent 6}}
+  {{- if .Values.enablePodAntiAffinity }}
+  strategy:
+    rollingUpdate:
+      maxUnavailable: 1
+  {{- end }}
   template:
     metadata:
       annotations:

charts/linkerd2/templates/destination.yaml

@@ -45,6 +45,11 @@ spec:
       {{.Values.global.controllerComponentLabel}}: destination
       {{.Values.global.controllerNamespaceLabel}}: {{.Values.global.namespace}}
       {{- include "partials.proxy.labels" .Values.global.proxy | nindent 6}}
+  {{- if .Values.enablePodAntiAffinity }}
+  strategy:
+    rollingUpdate:
+      maxUnavailable: 1
+  {{- end }}
   template:
     metadata:
       annotations:

charts/linkerd2/templates/identity.yaml

@@ -65,6 +65,11 @@ spec:
       {{.Values.global.controllerComponentLabel}}: identity
       {{.Values.global.controllerNamespaceLabel}}: {{.Values.global.namespace}}
       {{- include "partials.proxy.labels" .Values.global.proxy | nindent 6}}
+  {{- if .Values.enablePodAntiAffinity }}
+  strategy:
+    rollingUpdate:
+      maxUnavailable: 1
+  {{- end }}
   template:
     metadata:
       annotations:

charts/linkerd2/templates/proxy-injector.yaml

@@ -24,6 +24,11 @@ spec:
   selector:
     matchLabels:
       {{.Values.global.controllerComponentLabel}}: proxy-injector
+  {{- if .Values.enablePodAntiAffinity }}
+  strategy:
+    rollingUpdate:
+      maxUnavailable: 1
+  {{- end }}
   template:
     metadata:
       annotations:

charts/linkerd2/templates/sp-validator.yaml

@@ -43,6 +43,11 @@ spec:
   selector:
     matchLabels:
       {{.Values.global.controllerComponentLabel}}: sp-validator
+  {{- if .Values.enablePodAntiAffinity }}
+  strategy:
+    rollingUpdate:
+      maxUnavailable: 1
+  {{- end }}
   template:
     metadata:
       annotations:

charts/linkerd2/templates/tap.yaml

@@ -48,6 +48,11 @@ spec:
       {{.Values.global.controllerComponentLabel}}: tap
       {{.Values.global.controllerNamespaceLabel}}: {{.Values.global.namespace}}
       {{- include "partials.proxy.labels" .Values.global.proxy | nindent 6}}
+  {{- if .Values.enablePodAntiAffinity }}
+  strategy:
+    rollingUpdate:
+      maxUnavailable: 1
+  {{- end }}
   template:
     metadata:
       annotations: