From 56f7683cab971ca2dae4049c9489232e4a01e3ae Mon Sep 17 00:00:00 2001
From: Charith Ellawala <charithe@users.noreply.github.com>
Date: Thu, 5 Oct 2023 16:47:08 +0100
Subject: [PATCH] enhancement(helm): Add support for defining topology spread
 constraints (#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   | 20 +++++++++++++++++++
 .../charts/cerbos/templates/deployment.yaml   |  1 +
 deploy/charts/cerbos/values.yaml              |  6 ++++++
 3 files changed, 27 insertions(+)

diff --git a/deploy/charts/cerbos/templates/_helpers.tpl b/deploy/charts/cerbos/templates/_helpers.tpl
index ba94e3735..c3c1db9a3 100644
--- a/deploy/charts/cerbos/templates/_helpers.tpl
+++ b/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 }}
diff --git a/deploy/charts/cerbos/templates/deployment.yaml b/deploy/charts/cerbos/templates/deployment.yaml
index ee1fedc31..0fe2df64b 100644
--- a/deploy/charts/cerbos/templates/deployment.yaml
+++ b/deploy/charts/cerbos/templates/deployment.yaml
@@ -132,3 +132,4 @@ spec:
       tolerations:
         {{- toYaml . | nindent 8 }}
       {{- end }}
+      {{- include "cerbos.topologySpreadConstraints" . | nindent 6}}
diff --git a/deploy/charts/cerbos/values.yaml b/deploy/charts/cerbos/values.yaml
index bec899da6..9bc418713 100644
--- a/deploy/charts/cerbos/values.yaml
+++ b/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: []