Add multibases example with different namespace

Author: Liujingfang1

examples/multibases/README.md

@@ -123,4 +123,5 @@ test 1 == \
   $(kustomize build $DEMO_HOME | grep cluster-a-prod-myapp-pod | wc -l); \
   echo $?    
 ```
-
+Similarly to adding different `namePrefix` in different variants, one can also add different `namespace` and compose those variants in
+one _kustomization_. For more details, take a look at [multi-namespaces](multi-namespace.md).

examples/multibases/multi-namespace.md

@@ -0,0 +1,115 @@
+# Demo: multi namespaces with a common base
+
+`kustomize` supports defining multiple variants with different namespace, as overlays on a common base.
+
+It's possible to create an additional overlay to compose these variants together - just declare the overlays as the bases of a new kustomization. The following demonstrates this using a base that's just one pod.
+
+Define a place to work:
+
+<!-- @makeWorkplace @test -->
+```
+DEMO_HOME=$(mktemp -d)
+```
+
+Define a common base:
+<!-- @makeBase @test -->
+```
+BASE=$DEMO_HOME/base
+mkdir $BASE
+
+cat <<EOF >$BASE/kustomization.yaml
+resources:
+- pod.yaml
+EOF
+
+cat <<EOF >$BASE/pod.yaml
+apiVersion: v1
+kind: Pod
+metadata:
+  name: myapp-pod
+  labels:
+    app: myapp
+spec:
+  containers:
+  - name: nginx
+    image: nginx:1.7.9
+EOF
+```
+
+Define a variant in namespace-a overlaying base:
+<!-- @makeNamespaceA @test -->
+```
+NSA=$DEMO_HOME/namespace-a
+mkdir $NSA
+
+cat <<EOF >$NSA/kustomization.yaml
+bases:
+- ./../base
+resources:
+- namespace.yaml
+namespace: namespace-a
+EOF
+
+cat <<EOF >$NSA/namespace.yaml
+apiVersion: v1
+kind: Namespace
+metadata:
+  name: namespace-a
+EOF
+```
+
+Define a variant in namespace-b overlaying base:
+<!-- @makeNamespaceB @test -->
+```
+NSB=$DEMO_HOME/namespace-b
+mkdir $NSB
+
+cat <<EOF >$NSB/kustomization.yaml
+bases:
+- ./../base
+resources:
+- namespace.yaml
+namespace: namespace-b
+EOF
+
+cat <<EOF >$NSA/namespace.yaml
+apiVersion: v1
+kind: Namespace
+metadata:
+  name: namespace-b
+EOF
+```
+
+Then define a _Kustomization_ composing two variants together:
+<!-- @makeTopLayer @test -->
+```
+cat <<EOF >$DEMO_HOME/kustomization.yaml
+bases:
+- ./namespace-a
+- ./namespace-b
+EOF
+```
+
+Now the workspace has following directories
+> ```
+> .
+> ├── base
+> │   ├── kustomization.yaml
+> │   └── pod.yaml
+> ├── kustomization.yaml
+> ├── namespace-a
+> │   ├── kustomization.yaml
+> │   └── namespace.yaml
+> └── namespace-b
+>     ├── kustomization.yaml
+>     └── namespace.yaml
+> ```
+
+Confirm that the `kustomize build` output contains two pod objects from namespace-a and namespace-b.
+
+<!-- @confirmVariants @test -->
+```
+test 2 == \
+  $(kustomize build $DEMO_HOME| grep -B 4 "namespace: namespace-[ab]" | grep "name: myapp-pod" | wc -l); \
+  echo $?  
+```