三个Client

在Kubernetes上，通常需要Client来访问Kubernetes中的对象，目前最常用的是RESTClient, DynamicClient和ClientSet这三种Client。今天就先介绍下这三个Client基本含义及大概的用法。Demo的编写是参考了http://blog.csdn.net/column/details/14420.html ，非常感谢。

RESTClient

RESTClient是Kubernetes最基础的Client，直接负责与Request(RESTClient中的概念)打交道。下面的Demo就描述如何生成一个RESTClient，并用该RESTClient获取某具体Pod的详细信息。

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package main
import (
	"flag"
	"fmt"
	"k8s.io/client-go/pkg/runtime"
	"k8s.io/client-go/pkg/runtime/serializer"
	"k8s.io/client-go/pkg/api"
	v1 "k8s.io/client-go/pkg/api/v1"
	"k8s.io/client-go/pkg/api/unversioned"
	"k8s.io/client-go/rest"
	"k8s.io/client-go/tools/clientcmd"
)
func main() {
	kubeconfig := flag.String("kubeconfig", "/root/.kube/config", "Path to a kube config. Only required if out-of-cluster.")
	flag.Parse()
	config, err := clientcmd.BuildConfigFromFlags("", *kubeconfig)
	if err != nil {
		fmt.Println("BuildConfigFromFlags error")
	}
	groupversion := &unversioned.GroupVersion{"", "v1"}
	config.GroupVersion = groupversion
	config.APIPath = "/api"
	config.ContentType = runtime.ContentTypeJSON
	config.NegotiatedSerializer = serializer.DirectCodecFactory{CodecFactory: api.Codecs}
	restClient, err := rest.RESTClientFor(config)
	if err != nil {
		fmt.Println("RESTClientFor error")
	}
	pod := v1.Pod{}
	err = restClient.Get().Resource("pods").Namespace("default").Name("nginx-1487191267-b4w5j").Do().Into(&pod)
	if err != nil {
		fmt.Println("error")
	}
	fmt.Println(pod)
}

运行结果内容过多，略。

DynamicClient

RESTClient需要自己设置请求各属性，用起来很不方便。DynamicClient是对RESTClient的封装，支持动态设置访问类型。

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package main
import (
	"flag"
	"fmt"
	"reflect"
	"encoding/json"
	"k8s.io/client-go/pkg/api/v1"
	"k8s.io/client-go/pkg/api/unversioned"
	"k8s.io/client-go/dynamic"
	"k8s.io/client-go/tools/clientcmd"
	"k8s.io/client-go/rest"
)
func main() {
	kubeconfig := flag.String("kubeconfig", "/root/.kube/config", "Path to a kube config. Only required if out-of-cluster.")
	fmt.Println(kubeconfig)
	flag.Parse()
	config, err := clientcmd.BuildConfigFromFlags("", *kubeconfig)
	if err != nil {
		fmt.Println("error1")
	}
	// 生成dynamicClient
	gv := &unversioned.GroupVersion{"", "v1"}
	resource := &unversioned.APIResource{Name: "pods", Namespaced: true}
	config.ContentConfig = rest.ContentConfig{GroupVersion: gv}
	config.APIPath = "/api"
	dynamicClient, err := dynamic.NewClient(config)
	if err != nil {
		fmt.Println("dynamic NewCLient error")
	}
	// 获取所有namespace的pod列表
	obj, err := dynamicClient.Resource(resource, "").List(&v1.ListOptions{})
	if err != nil {
		fmt.Println("dynamicClient Resource error")
	}
	js, err := json.Marshal(reflect.ValueOf(obj).Elem().Interface())
	if err != nil {
		fmt.Println("error")
	}
	podlist := v1.PodList{}
	json.Unmarshal(js, &podlist)
	fmt.Println(podlist)
	fmt.Println("------------------------")
	// 获取具体具体pod
	obj, err = dynamicClient.Resource(resource, "default").Get("nginx-1487191267-b4w5j")
        if err != nil {
                fmt.Println("dynamicClient Resource error")
        }
        js, err = json.Marshal(obj)
        if err != nil {
                fmt.Println("error")
        }
        pod := v1.Pod{}
        json.Unmarshal(js, &pod)
        fmt.Println(pod)
}

运行结果内容过多，略。

ClientSet

ClientSet也是对RESTClient的一种封装，与DynamicClient不同的是，ClientSet支持衍生出具体资源的Client，如PodClient等。ClientSet是Kubernetes用的最多的Client类型 。

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package main
import (
	"flag"
	"fmt"
	apiv1 "k8s.io/client-go/pkg/api/v1"
	"k8s.io/client-go/kubernetes"
	"k8s.io/client-go/tools/clientcmd"
)
func main() {
	kubeconfig := flag.String("kubeconfig", "/root/.kube/config", "Path to a kube config. Only required if out-of-cluster.")
	fmt.Println(kubeconfig)
	flag.Parse()
	config, err := clientcmd.BuildConfigFromFlags("", *kubeconfig)
	if err != nil {
		fmt.Println("error")
	}
	// 生成clientset
	clientset, err := kubernetes.NewForConfig(config)
	if err != nil {
		fmt.Println("error")
	}
	// 生成podCLient
	podClient := clientset.Core().Pods("")
	pods, err := podClient.List(apiv1.ListOptions{})
	if err != nil {
		fmt.Println("error")
	}
	for _, pod := range pods.Items {
		fmt.Println(pod)
	}
}

运行结果内容过多，略。