I have the following YAML file -
apiVersion: v1
kind: Service
metadata:
labels:
name: mariadb
name: mariadb
spec:
ports:
- port: 3306
selector:
name: mariadbWhen this service is created, a ClusterIP is automatically set. My stateful set 'mariadb' is exposed using this service. But if I login to another pod on Kubernetes, I cannot ping this pod using
ping mariadb-0.mariadb.[namespace].svc.cluster.localIt also does not work if the ServiceType is set to 'NodePort'.
If I update the service to
apiVersion: v1
kind: Service
metadata:
labels:
name: mariadb
name: mariadb
spec:
ports:
- port: 3306
clusterIP: None
selector:
name: mariadbWhen I login to another pod on Kubernetes, I can ping this pod using
ping mariadb-0.mariadb.[namespace].svc.cluster.localIs there any reason why this internal url is not accessible when the ClusterIP is set?
The key is 'clusterIP: None'.
If clusterIP is not set, k8s will allocate one for the service automatically, also the kube-dns will set a domain name for the service, named mariadb.[namespace].svc.cluster.local, that's your first case.
While if clusterIP is set to 'None', that means k8s doesn't allocate a ip for the service, in this case, kube-dns will set a domain name for every endpoints that the service points to, in your second case, it's mariadb-0.mariadb.[namespace].svc.cluster.local.
Also you can set clusterIP to a ip address, in that case, it's the same as your first case.
That's why you can ping mariadb-0.mariadb.[namespace].svc.cluster.local in your second case, while can't in your first case.