ClusterIP Services allow workloads in the same cluster to use their cluster-internal domain names to access each other.
The cluster-internal domain name format is <Service name>.<Namespace of the workload>.svc.cluster.local:<Port>, for example, nginx.default.svc.cluster.local:80.
Figure 1 shows the mapping relationships between access channels, container ports, and access ports.
You can set the access type (Service) when creating a workload on the CCE console.
You can set the Service after creating a workload. This has no impact on the workload status and takes effect immediately. The procedure is as follows:
You can run kubectl commands to set the access type (Service). This section uses a Nginx workload as an example to describe how to implement intra-cluster access using kubectl.
The file names are user-defined. nginx-deployment.yaml and nginx-clusterip-svc.yaml are merely example file names.
apiVersion: apps/v1 kind: Deployment metadata: name: nginx spec: replicas: 1 selector: matchLabels: app: nginx template: metadata: labels: app: nginx spec: containers: - image: nginx:latest name: nginx imagePullSecrets: - name: default-secret
apiVersion: v1 kind: Service metadata: labels: app: nginx name: nginx-clusterip spec: ports: - name: service0 port: 8080 # Port for accessing a Service. protocol: TCP # Protocol used for accessing a Service. The value can be TCP or UDP. targetPort: 80 # Port used by a Service to access the target container. This port is closely related to the applications running in a container. In this example, the Nginx image uses port 80 by default. selector: # Label selector. A Service selects a pod based on the label and forwards the requests for accessing the Service to the pod. In this example, select the pod with the app:nginx label. app: nginx type: ClusterIP # Type of a Service. ClusterIP indicates that a Service is only reachable from within the cluster.
kubectl create -f nginx-deployment.yaml
If information similar to the following is displayed, the workload has been created.
deployment "nginx" created
kubectl get po
If information similar to the following is displayed, the workload is running.
NAME READY STATUS RESTARTS AGE nginx-2601814895-znhbr 1/1 Running 0 15s
kubectl create -f nginx-clusterip-svc.yaml
If information similar to the following is displayed, the Service is being created.
service "nginx-clusterip" created
kubectl get svc
If information similar to the following is displayed, the Service has been created, and a cluster-internal IP address has been assigned to the Service.
# kubectl get svc NAME TYPE CLUSTER-IP EXTERNAL-IP PORT(S) AGE kubernetes ClusterIP 10.247.0.1 <none> 443/TCP 4d6h nginx-clusterip ClusterIP 10.247.74.52 <none> 8080/TCP 14m
A Service can be accessed from containers or nodes in a cluster.
Create a pod, access the pod, and run the curl command to access IP address:Port or the domain name of the Service, as shown in the following figure.
The domain name suffix can be omitted. In the same namespace, you can directly use nginx-clusterip:8080 for access. In other namespaces, you can use nginx-clusterip.default:8080 for access.
# kubectl run -i --tty --image nginx:alpine test --rm /bin/sh If you don't see a command prompt, try pressing enter. / # curl 10.247.74.52:8080 <!DOCTYPE html> <html> <head> <title>Welcome to nginx!</title> <style> body { width: 35em; margin: 0 auto; font-family: Tahoma, Verdana, Arial, sans-serif; } </style> </head> <body> <h1>Welcome to nginx!</h1> <p>If you see this page, the nginx web server is successfully installed and working. Further configuration is required.</p> <p>For online documentation and support please refer to <a href="http://nginx.org/">nginx.org</a>.<br/> Commercial support is available at <a href="http://nginx.com/">nginx.com</a>.</p> <p><em>Thank you for using nginx.</em></p> </body> </html> / # curl nginx-clusterip.default.svc.cluster.local:8080 ... <h1>Welcome to nginx!</h1> ... / # curl nginx-clusterip.default:8080 ... <h1>Welcome to nginx!</h1> ... / # curl nginx-clusterip:8080 ... <h1>Welcome to nginx!</h1> ...