fix(chart): omit api-server spec.replicas when HPA is enabled

Author: thejoeejoee

chart/templates/api-server/api-server-deployment.yaml

@@ -47,7 +47,9 @@ metadata:
   annotations: {{- toYaml .Values.apiServer.annotations | nindent 4 }}
   {{- end }}
 spec:
+  {{- if not .Values.apiServer.hpa.enabled }}
   replicas: {{ .Values.apiServer.replicas }}
+  {{- end }}
   {{- if ne $revisionHistoryLimit "" }}
   revisionHistoryLimit: {{ $revisionHistoryLimit }}
   {{- end }}

chart/values.schema.json

@@ -6179,8 +6179,11 @@
                     }
                 },
                 "replicas": {
-                    "description": "How many Airflow API server replicas should run. This setting is ignored when HPA (Horizontal Pod Autoscaler) is enabled",
-                    "type": "integer",
+                    "description": "How many Airflow API server replicas should run. Set to null (~) when HPA is enabled to omit the field from the Deployment and let HPA exclusively control the replica count.",
+                    "type": [
+                        "integer",
+                        "null"
+                    ],
                     "default": 1
                 },
                 "revisionHistoryLimit": {

chart/values.yaml

@@ -1748,9 +1748,9 @@ migrateDatabaseJob:
 
 apiServer:
   enabled: true
-  # Number of Airflow API servers in the deployment
-  # This setting is ignored when HPA (Horizontal Pod Autoscaler) is enabled,
-  # as HPA will automatically manage the number of replicas based on the configured metrics.
+  # Number of Airflow API servers in the deployment.
+  # Set to ~ (null) when HPA is enabled so the replicas field is omitted from the Deployment,
+  # letting HPA exclusively control the replica count.
   replicas: 1
   # Max number of old replicasets to retain
   revisionHistoryLimit: ~

helm-tests/tests/helm_tests/apiserver/test_hpa_apiserver.py

@@ -32,10 +32,32 @@ def test_hpa_disabled_by_default(self):
         )
         assert docs == []
 
+    def test_replicas_omitted_when_null(self):
+        """When apiServer.replicas is null the Deployment must not contain spec.replicas."""
+        docs = render_chart(
+            values={
+                "apiServer": {
+                    "replicas": None,
+                    "hpa": {"enabled": True},
+                },
+            },
+            show_only=["templates/api-server/api-server-deployment.yaml"],
+        )
+        assert jmespath.search("spec.replicas", docs[0]) is None
+
+    def test_replicas_present_when_set(self):
+        """When apiServer.replicas is a number the Deployment must contain spec.replicas."""
+        docs = render_chart(
+            values={
+                "apiServer": {"replicas": 3},
+            },
+            show_only=["templates/api-server/api-server-deployment.yaml"],
+        )
+        assert jmespath.search("spec.replicas", docs[0]) == 3
+
     def test_should_add_component_specific_labels(self):
         docs = render_chart(
             values={
-                "airflowVersion": "3.0.2",
                 "apiServer": {
                     "hpa": {"enabled": True},
                     "labels": {"test_label": "test_label_value"},
@@ -58,7 +80,6 @@ def test_min_max_replicas(self, min_replicas, max_replicas):
         """Verify minimum and maximum replicas."""
         docs = render_chart(
             values={
-                "airflowVersion": "3.0.2",
                 "apiServer": {
                     "hpa": {
                         "enabled": True,
@@ -82,7 +103,6 @@ def test_hpa_behavior(self):
         }
         docs = render_chart(
             values={
-                "airflowVersion": "3.0.2",
                 "apiServer": {
                     "hpa": {
                         "enabled": True,
@@ -129,7 +149,6 @@ def test_hpa_behavior(self):
     def test_should_use_hpa_metrics(self, metrics, expected_metrics):
         docs = render_chart(
             values={
-                "airflowVersion": "3.0.2",
                 "apiServer": {
                     "hpa": {"enabled": True, **({"metrics": metrics} if metrics else {})},
                 },