add feature gates support in Helm templates (#531)

Issue #, if available: N/A, but related to aws-controllers-k8s/runtime#151

Description of changes: Adds optional support for feature gates in Helm templates.  A top-level key of `featureGates` has been added to the default values file template, and the optional command-line argument has been appended to the deployment template.

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.

Author: eadasiak

templates/helm/templates/_helpers.tpl.tpl

@@ -51,4 +51,13 @@
 {{ "{{/* The rules a of ClusterRole or Role */}}" }}
 {{ DefineTemplate "rbac-rules" }}
 SEDREPLACERULES
-{{ "{{- end }}" }}
+{{ "{{- end }}" }}
+
+{{ "{{/* Convert k/v map to string like: \"key1=value1,key2=value2,...\" */}}" }}
+{{ DefineTemplate "feature-gates" }}
+{{ "{{- $list := list -}}" }}
+{{ "{{- range $k, $v := .Values.featureGates -}}" }}
+{{ "{{- $list = append $list (printf \"%s=%s\" $k ( $v | toString)) -}}" }}
+{{ "{{- end -}}" }}
+{{ "{{ join \",\" $list }}" }}
+{{ "{{- end -}}" }}

templates/helm/templates/deployment.yaml.tpl

@@ -79,6 +79,10 @@ spec:
 {{ "{{- range $key, $value := .Values.reconcile.resourceMaxConcurrentSyncs }}" }}
         - --reconcile-resource-max-concurrent-syncs
         - {{ "\"$(RECONCILE_RESOURCE_MAX_CONCURRENT_SYNCS_{{ $key | upper }})\"" }}
+{{ "{{- end }}" }}
+{{ "{{- if .Values.featureGates}}" }}
+        - --feature-gates
+        - "$(FEATURE_GATES)"
 {{ "{{- end }}" }}
         image: {{ "{{ .Values.image.repository }}:{{ .Values.image.tag }}" }}
         imagePullPolicy: {{ "{{ .Values.image.pullPolicy }}" }}
@@ -122,6 +126,10 @@ spec:
 {{ "{{- range $key, $value := .Values.reconcile.resourceMaxConcurrentSyncs }}" }}
         - name: {{ "RECONCILE_RESOURCE_MAX_CONCURRENT_SYNCS_{{ $key | upper }}" }}
           value: {{ "{{ $key }}={{ $value }}" }}
+{{ "{{- end }}" }}
+{{ "{{- if .Values.featureGates}}" }}
+        - name: FEATURE_GATES
+          value: {{ IncludeTemplate "feature-gates" }}
 {{ "{{- end }}" }}
         {{ "{{- if .Values.aws.credentials.secretName }}" }}
         - name: AWS_SHARED_CREDENTIALS_FILE

templates/helm/values.schema.json

@@ -268,6 +268,13 @@
       "type": "object"
     }
   },
+  "featureGates": {
+    "description": "Feature gates settings",
+    "type": "object",
+    "additionalProperties": {
+      "type": "boolean"
+    }
+  },
   "required": [
     "image",
     "deployment",

templates/helm/values.yaml.tpl

@@ -153,3 +153,10 @@ leaderElection:
   # will attempt to use the namespace of the service account mounted to the Controller
   # pod.
   namespace: ""
+
+# Configuration for feature gates.  These are optional controller features that
+# can be individually enabled ("true") or disabled ("false") by adding key/value
+# pairs below.
+featureGates: {}
+  # featureGate1: true
+  # featureGate2: false