By default, the components of an application are in the same namespace that the application is in as the Kubernetes resources are all created in the same namespace. The default behavior of Kubernetes Application Navigator is to scope the label selector specified in the Application Custom Resource to the namespace that the label selector was created in. This behavior means that the label selector of an application is applied only to the specified component kinds in the same namespace as the application.
Components from other namespaces can be included in the label selector search by listing multiple namespaces within a comma-delimited list on the kappnav.component.namespaces annotation in the Application custom resource.
Spanning namespaces is valuable when an application is composed of multiple microservices that are created and managed by teams that deploy to isolated namespaces.
In the following example, a business application that is named music-service is composed of microservices that are created by the user interface team and the API team.
Each team is responsible for creating multiple microservices, and they organize themselves into either the ui-namespace or the api-namespace. The teams develop and deploy multiple microservices in their respective namespaces.
The music-service application uses the web-ui that is developed by the user interface team and the streaming-api that is developed by the API team.
To create an Application custom resource that reflects the music-service application, more configuration is needed to instruct Kubernetes Application Navigator to span the namespaces:
metadata:
annotations:
kappnav.component.namespaces: ui-namespace, api-namespace
The optional kappnav.component.namespaces annotation instructs Kubernetes Application Navigator to apply the label selector of the application to the 'ui-namespace' and 'api-namespace' namespaces in addition to the namespace of the application.
The music-service sample application uses the solution: music-service label to group all of the resources together.
The following music-service-app-cr.yaml file is the YAML file of the sample application:
$ kubectl get application music-service -n music-service -o yaml
apiVersion: app.k8s.io/v1beta1
kind: Application
metadata:
name: music-service
annotations:
kappnav.component.namespaces: ui-namespace, api-namespace
labels:
app: music-service
solution: music-service
spec:
componentKinds:
- group: resources
kind: Pod
- group: resources
kind: Deployment
- group: resources
kind: Service
- group: resources
kind: Route
selector:
matchLabels:
solution: music-service