K8s获取NodePort

(金庆的专栏 2018.9)

将服务用NodePort暴露到外网，为避免端口冲突，不指定NodePort,
而是让k8s自动选择一个端口。

$ cat get_node_port.yaml
kind: Service
apiVersion: v1
metadata:
  name: jq-service
spec:
  type: NodePort
  selector:
    app: MyApp
  ports:
  - protocol: TCP
    port: 80

$ kubectl apply -f get_node_port.yaml
service "jq-service" configured
$ kubectl describe svc/jq-service
Name:                     jq-service
Namespace:                default
Labels:                   <none>
Annotations:              kubectl...
Selector:                 app=MyApp
Type:                     NodePort
IP:                       10.104.228.187
Port:                     <unset>  80/TCP
TargetPort:               80/TCP
NodePort:                 <unset>  32115/TCP
Endpoints:                <none>
Session Affinity:         None
External Traffic Policy:  Cluster
Events:                   <none>

可以看到k8s分配了NodePort 32115。

然后需要获取这个动态的NodePort，以通知客户端连接该端口。

cat main.go
package main

import (
    "context"
    "fmt"
    "log"
    "io/ioutil"

    "github.com/ghodss/yaml"
    "github.com/ericchiang/k8s"
    corev1 "github.com/ericchiang/k8s/apis/core/v1"
)

func main() {
    data, err := ioutil.ReadFile("config")
    if err != nil {
        panic(err)
    }

    // Unmarshal YAML into a Kubernetes config object.
    var config k8s.Config
    if err := yaml.Unmarshal(data, &config); err != nil {
        panic(err)
    }

    client, err := k8s.NewClient(&config)
    // client, err := k8s.NewInClusterClient()
    if err != nil {
        log.Fatal(err)
    }

    var svc corev1.Service
    if err := client.Get(context.Background(), "default", "jq-service", &svc); err != nil {
        log.Fatal(err)
    }
    fmt.Printf("%d\n", *svc.Spec.Ports[0].NodePort)
}

运行时需要复制config: cp ~/.kube/config .