fix: preserve existing flags when applying metrics patch

Ensure that enabling the manager_metrics_patch.yaml in config/default/kustomization.yaml does not overwrite existing arguments in config/manager/manager.yaml. The patch now appends the --metrics-bind-address argument without replacing other arguments.

More info: #3934

Author: camilamacedo86

.github/workflows/test-sample-go.yml

@@ -24,9 +24,9 @@ jobs:
         run: |
           KUSTOMIZATION_FILE_PATH="testdata/project-v4/config/default/kustomization.yaml"
           sed -i '25s/^#//' $KUSTOMIZATION_FILE_PATH
-          sed -i '27s/^#//' $KUSTOMIZATION_FILE_PATH
-          sed -i '42s/^#//' $KUSTOMIZATION_FILE_PATH
-          sed -i '46,142s/^#//' $KUSTOMIZATION_FILE_PATH
+          sed -i '39s/^#//' $KUSTOMIZATION_FILE_PATH
+          sed -i '44s/^#//' $KUSTOMIZATION_FILE_PATH
+          sed -i '48,144s/^#//' $KUSTOMIZATION_FILE_PATH
       
       - name: Test
         run: |

docs/book/src/cronjob-tutorial/testdata/project/cmd/main.go

@@ -76,7 +76,8 @@ func main() {
 	var probeAddr string
 	var secureMetrics bool
 	var enableHTTP2 bool
-	flag.StringVar(&metricsAddr, "metrics-bind-address", ":8080", "The address the metric endpoint binds to.")
+	flag.StringVar(&metricsAddr, "metrics-bind-address", "0", "The address the metric endpoint binds to. "+
+		"Use the port :8080. If not set, it will be '0 in order to disable the metrics server")
 	flag.StringVar(&probeAddr, "health-probe-bind-address", ":8081", "The address the probe endpoint binds to.")
 	flag.BoolVar(&enableLeaderElection, "leader-elect", false,
 		"Enable leader election for controller manager. "+

docs/book/src/cronjob-tutorial/testdata/project/config/default/kustomization.yaml

@@ -31,6 +31,8 @@ patches:
 # More info: https://book.kubebuilder.io/reference/metrics
 # If you want to expose the metric endpoint of your controller-manager uncomment the following line.
 #- path: manager_metrics_patch.yaml
+#  target:
+#    kind: Deployment
 
 # [WEBHOOK] To enable webhook, uncomment all the sections with [WEBHOOK] prefix including the one in
 # crd/kustomization.yaml

docs/book/src/cronjob-tutorial/testdata/project/config/default/manager_metrics_patch.yaml

@@ -1,13 +1,4 @@
 # This patch adds the args to allow exposing the metrics endpoint securely
-apiVersion: apps/v1
-kind: Deployment
-metadata:
-  name: controller-manager
-  namespace: system
-spec:
-  template:
-    spec:
-      containers:
-      - name: manager
-        args:
-        - "--metrics-bind-address=0.0.0.0:8080"
+- op: add
+  path: /spec/template/spec/containers/0/args/0
+  value: --metrics-bind-address=:8080

docs/book/src/cronjob-tutorial/testdata/project/config/manager/manager.yaml

@@ -63,7 +63,6 @@ spec:
         args:
           - --leader-elect
           - --health-probe-bind-address=:8081
-          - --metrics-bind-address=0
         image: controller:latest
         name: manager
         securityContext:

docs/book/src/getting-started/testdata/project/cmd/main.go

@@ -57,7 +57,8 @@ func main() {
 	var probeAddr string
 	var secureMetrics bool
 	var enableHTTP2 bool
-	flag.StringVar(&metricsAddr, "metrics-bind-address", ":8080", "The address the metric endpoint binds to.")
+	flag.StringVar(&metricsAddr, "metrics-bind-address", "0", "The address the metric endpoint binds to. "+
+		"Use the port :8080. If not set, it will be '0 in order to disable the metrics server")
 	flag.StringVar(&probeAddr, "health-probe-bind-address", ":8081", "The address the probe endpoint binds to.")
 	flag.BoolVar(&enableLeaderElection, "leader-elect", false,
 		"Enable leader election for controller manager. "+

docs/book/src/getting-started/testdata/project/config/default/kustomization.yaml

@@ -31,6 +31,8 @@ patches:
 # More info: https://book.kubebuilder.io/reference/metrics
 # If you want to expose the metric endpoint of your controller-manager uncomment the following line.
 #- path: manager_metrics_patch.yaml
+#  target:
+#    kind: Deployment
 
 # [WEBHOOK] To enable webhook, uncomment all the sections with [WEBHOOK] prefix including the one in
 # crd/kustomization.yaml

docs/book/src/getting-started/testdata/project/config/default/manager_metrics_patch.yaml

@@ -1,13 +1,4 @@
 # This patch adds the args to allow exposing the metrics endpoint securely
-apiVersion: apps/v1
-kind: Deployment
-metadata:
-  name: controller-manager
-  namespace: system
-spec:
-  template:
-    spec:
-      containers:
-      - name: manager
-        args:
-        - "--metrics-bind-address=0.0.0.0:8080"
+- op: add
+  path: /spec/template/spec/containers/0/args/0
+  value: --metrics-bind-address=:8080

docs/book/src/getting-started/testdata/project/config/manager/manager.yaml

@@ -63,7 +63,6 @@ spec:
         args:
           - --leader-elect
           - --health-probe-bind-address=:8081
-          - --metrics-bind-address=0
         image: controller:latest
         name: manager
         env:

docs/book/src/reference/metrics.md

@@ -46,9 +46,12 @@ First, you will need enable the Metrics by uncommenting the following line
 in the file `config/default/kustomization.yaml`, see:
 
 ```sh
-# [Metrics] The following patch will enable the metrics endpoint.
-# Ensure that you also protect this endpoint.
+# [METRICS] The following patch will enable the metrics endpoint. Ensure that you also protect this endpoint.
+# More info: https://book.kubebuilder.io/reference/metrics
+# If you want to expose the metric endpoint of your controller-manager uncomment the following line.
 #- path: manager_metrics_patch.yaml
+#  target:
+#    kind: Deployment
 ```
 
 Note that projects are scaffolded by default passing the flag `--metrics-bind-address=0`