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Service Operations

• Create a service
  • Service configuration file
  • Sample files
• View a service
• Delete a service

Services map a port on each cluster node to ports on one or more pods.

The mapping uses a selector key:value pair in the service, and the labels property of pods. Any pods whose labels match the service selector are made accessible through the service’s port.

For more information, see the Services Overview.

Create a service

Services are created by passing a configuration file to the kubectl create command:

$ kubectl create -f FILE

Where:

• -f FILE or --filename FILE is a relative path to a service configuration file in either JSON or YAML format.

A successful service create request returns the service name. You can use a sample file below to try a create request.

Service configuration file

When creating a service, you must point to a service configuration file as the value of the -f flag. The configuration file can be formatted as YAML or as JSON, and supports the following fields:

{
  "kind": "Service",
  "apiVersion": "v1",
  "metadata": {
    "name": string
  },
  "spec": {
    "ports": [{
      "port": int,
      "targetPort": int
    }],
    "selector": {
      string: string
    },
    "type": "LoadBalancer"
  }
}

Required fields are:

• kind: Always Service.
• apiVersion: Currently v1.
• metadata: Contains:
  • name: The name to give to this service.
• spec: Contains:
  • ports: The ports to map. port is the service port to expose on the cluster IP. targetPort is the port to target on the pods that are part of this service.
  • selector: The label key:value pair that defines the pods to target.
  • type: Optional. If the type is LoadBalancer, sets up a network load balancer for your service. This provides an externally-accessible IP address that sends traffic to the correct port on your cluster nodes.

For the full service schema see the Kubernetes api reference.

Sample files

The following service configuration files assume that you have a set of pods that expose port 9376 and carry the label app=example.

Both files create a new service named myapp which resolves to TCP port 9376 on any pod with the app=example label.

The difference in the files is in how the service is accessed. The first file does not create an external load balancer; the service can be accessed through port 8765 on any of the nodes’ IP addresses.

• JSON
• YAML

service-sample.json
{ "kind": "Service", "apiVersion": "v1", "metadata": { "name": "myapp" }, "spec": { "ports": [{ "port": 8765, "targetPort": 9376 }], "selector": { "app": "example" } } }

service-sample.yaml
apiVersion: v1 kind: Service metadata: name: myapp spec: ports: - port: 8765 targetPort: 9376 selector: app: example

The second file uses network load balancing to create a single IP address that spreads traffic to all of the nodes in your cluster. This option is specified with the "type": "LoadBalancer" property.

• JSON
• YAML

load-balancer-sample.json
{ "kind": "Service", "apiVersion": "v1", "metadata": { "name": "myapp" }, "spec": { "ports": [{ "port": 8765, "targetPort": 9376 }], "selector": { "app": "example" }, "type": "LoadBalancer" } }

load-balancer-sample.yaml
apiVersion: v1 kind: Service metadata: name: myapp spec: ports: - port: 8765 targetPort: 9376 selector: app: example type: LoadBalancer

To access the service, a client connects to the external IP address, which forwards to port 8765 on a node in the cluster, which in turn accesses port 9376 on the pod. See the Service configuration file section of this doc for directions on finding the external IP address.

View a service

To list all services on a cluster, use the kubectl get command:

$ kubectl get services

A successful get request returns all services that exist on the specified cluster:

NAME    LABELS   SELECTOR    IP              PORT
myapp   <none>   app=MyApp   10.123.255.83   8765/TCP

To return information about a specific service, use the kubectl describe command:

$ kubectl describe service NAME

Details about the specific service are returned:

Name:                   myapp
Labels:                 <none>
Selector:               app=MyApp
IP:                     10.123.255.83
Port:                   <unnamed>       8765/TCP
NodePort:               <unnamed>       31474/TCP
Endpoints:              <none>
Session Affinity:       None
No events.

To return information about a service when event information is not required, substitute get for describe.

Delete a service

To delete a service, use the kubectl delete command:

$ kubectl delete service NAME

A successful delete request returns the deleted service’s name.