Add example for replicas in kustomization.yaml

examples/replicas.md

@@ -0,0 +1,67 @@
+# Demo: change replicas
+
+
+Define a place to work:
+
+<!-- @makeWorkplace @testAgainstLatestRelease -->
+```
+DEMO_HOME=$(mktemp -d)
+```
+
+Make a `kustomization` containing a deployment resource with replicas
+
+<!-- @createKustomization @testAgainstLatestRelease -->
+```
+cat <<EOF >$DEMO_HOME/kustomization.yaml
+resources:
+- deployment.yaml
+replicas:
+- name: myapp
+  count: 3
+EOF
+```
+
+Declare the deployment resource
+
+<!-- @createDeployment @testAgainstLatestRelease -->
+```
+cat <<EOF >$DEMO_HOME/pod.yaml
+apiVersion: apps/v1
+kind: Deployment
+metadata:
+  labels:
+    app: myapp
+  name: myapp
+spec:
+  replicas: 1
+  selector:
+    matchLabels:
+      app: myapp
+  template:
+    metadata:
+      labels:
+        app: nginx
+    spec:
+      containers:
+      - name: myapp-container
+        image: busybox:1.29.0
+EOF
+```
+
+The `myapp` resource declares an deployment managing a pod running a busybox container.
+
+
+Now build this `kustomization`
+<!-- @kustomizeBuild @testAgainstLatestRelease -->
+```
+kustomize build $DEMO_HOME
+```
+
+Confirm that this replaces replicas for myapp:
+
+<!-- @confirmImages @testAgainstLatestRelease -->
+```
+test 3 = \
+  $(kustomize build $DEMO_HOME | grep replicas | awk '{print $2}); \
+  echo $?
+```