enhancement(helm): Add support for defining topology spread constrain…

…ts (#1821)

* Add topologySpreadConstraints to the helm chart

Signed-off-by: Piotr Solarczyk <psolarcz@cisco.com>

* Use a template function

Signed-off-by: Charith Ellawala <charith@cerbos.dev>

---------

Signed-off-by: Piotr Solarczyk <psolarcz@cisco.com>
Signed-off-by: Charith Ellawala <charith@cerbos.dev>
Co-authored-by: Piotr Solarczyk <psolarcz@cisco.com>

deploy/charts/cerbos/templates/_helpers.tpl

@@ -167,3 +167,23 @@ The image reference to use in pods
 {{- end -}}
 "
 {{- end }}
+
+{{/*
+Topology spread constraints with label selector injected
+*/}}
+{{- define "cerbos.topologySpreadConstraints" -}}
+{{- if .Values.topologySpreadConstraints }}
+{{- $defaultLabels := (fromYaml (include "cerbos.selectorLabels" $)) }}
+{{- $defaultLabelSelector := (dict "labelSelector" (dict "matchLabels" $defaultLabels)) }}
+{{- $constraints := list }}
+{{- range $c := .Values.topologySpreadConstraints }}
+{{- if (hasKey $c "labelSelector") }}
+{{- $constraints = (append $constraints $c) }}
+{{- else }}
+{{- $constraints = (append $constraints (mergeOverwrite $c $defaultLabelSelector)) }}
+{{- end }}
+{{- end }}
+topologySpreadConstraints:
+{{ toYaml $constraints | indent 2 }}
+{{- end }}
+{{- end }}

deploy/charts/cerbos/templates/deployment.yaml

@@ -132,3 +132,4 @@ spec:
       tolerations:
         {{- toYaml . | nindent 8 }}
       {{- end }}
+      {{- include "cerbos.topologySpreadConstraints" . | nindent 6}}

deploy/charts/cerbos/values.yaml

@@ -79,6 +79,12 @@ tolerations: []
 # Pod affinity rules.
 affinity: {}
 
+# Topology Spread Constraints rules.
+topologySpreadConstraints: []
+  # - topologyKey: topology.kubernetes.io/zone
+  #   maxSkew: 1
+  #   whenUnsatisfiable: ScheduleAnyway
+
 # Volumes to add to the pod.
 volumes: []