Kubernetes - Labels & Selectors
Labels are key-value pairs which are attached to pods, replication controller and services. They are used as identifying attributes for objects such as pods and replication controller. They can be added to an object at creation time and can be added or modified at the run time.
Labels do not provide uniqueness. In general, we can say many objects can carry the same labels. Labels selector are core grouping primitive in Kubernetes. They are used by the users to select a set of objects.
Kubernetes API currently supports two type of selectors −
- Equality-based selectors
- Set-based selectors
They allow filtering by key and value. Matching objects should satisfy all the specified labels.
Set-based selectors allow filtering of keys according to a set of values.
apiVersion: v1 kind: Service metadata: name: sp-neo4j-standalone spec: ports: - port: 7474 name: neo4j type: NodePort selector: app: salesplatform ---------> 1 component: neo4j -----------> 2
In the above code, we are using the label selector as app: salesplatform and component as component: neo4j.
Once we run the file using the kubectl command, it will create a service with the name sp-neo4j-standalone which will communicate on port 7474. The ype is NodePort with the new label selector as app: salesplatform and component: neo4j.