adding optional support for topologySpreadConstraints to helm chart (#2575)

* adding support for topologySpreadConstraints

* update readme

Author: stensonb

helm/aws-load-balancer-controller/README.md

@@ -177,6 +177,7 @@ The default values set by the application itself can be confirmed [here](https:/
 | `nodeSelector`                                 | Node labels for controller pod assignment                                                                | `{}`                                                                               |
 | `tolerations`                                  | Controller pod toleration for taints                                                                     | `{}`                                                                               |
 | `affinity`                                     | Affinity for pod assignment                                                                              | `{}`                                                                               |
+| `topologySpreadConstraints`                    | Topology Spread Constraints for pod assignment                                                           | `{}`                                                                               |
 | `podAnnotations`                               | Annotations to add to each pod                                                                           | `{}`                                                                               |
 | `podLabels`                                    | Labels to add to each pod                                                                                | `{}`                                                                               |
 | `rbac.create`                                  | if `true`, create and use RBAC resources                                                                 | `true`                                                                             |

helm/aws-load-balancer-controller/templates/deployment.yaml

@@ -196,3 +196,7 @@ spec:
       {{- if .Values.priorityClassName }}
       priorityClassName: {{ .Values.priorityClassName | quote }}
       {{- end }}
+      {{- with .Values.topologySpreadConstraints }}
+      topologySpreadConstraints:
+        {{- toYaml . | nindent 8 }}
+      {{- end }}

helm/aws-load-balancer-controller/test.yaml

@@ -63,6 +63,13 @@ tolerations: []
 
 affinity: {}
 
+# topologySpreadConstraints is a stable feature of k8s v1.19 which provides the ability to
+# control how Pods are spread across your cluster among failure-domains such as regions, zones,
+# nodes, and other user-defined topology domains.
+# 
+# more details here: https://kubernetes.io/docs/concepts/workloads/pods/pod-topology-spread-constraints/
+topologySpreadConstraints: {}
+
 podAnnotations: {}
 
 podLabels: {}

helm/aws-load-balancer-controller/values.yaml

@@ -67,6 +67,13 @@ tolerations: []
 
 affinity: {}
 
+# topologySpreadConstraints is a stable feature of k8s v1.19 which provides the ability to
+# control how Pods are spread across your cluster among failure-domains such as regions, zones,
+# nodes, and other user-defined topology domains.
+# 
+# more details here: https://kubernetes.io/docs/concepts/workloads/pods/pod-topology-spread-constraints/
+topologySpreadConstraints: {}
+
 updateStrategy: {}
   # type: RollingUpdate
   # rollingUpdate: