显然，dynamicClient还需要用户自己设置resource资源。其实更多的时候用户只是希望如果要操作pod，那么生成一个podClient；如果要操作service，那么 生成一个serviceClient。ClientSet就是满足用户的这种需要。

ClientSet

ClientSet是多个Client的集合，定义在/pkg/client/clientset_generated/release_1_5/clientset.go中：

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// Clientset contains the clients for groups. Each group has exactly one
// version included in a Clientset.
//***Fankang***//
//***v1.5中的client***//
type Clientset struct {
	*discovery.DiscoveryClient
	*v1core.CoreV1Client
	*v1beta1apps.AppsV1beta1Client
	*v1beta1authentication.AuthenticationV1beta1Client
	*v1beta1authorization.AuthorizationV1beta1Client
	*v1autoscaling.AutoscalingV1Client
	*v1batch.BatchV1Client
	*v2alpha1batch.BatchV2alpha1Client
	*v1alpha1certificates.CertificatesV1alpha1Client
	*v1beta1extensions.ExtensionsV1beta1Client
	*v1beta1policy.PolicyV1beta1Client
	*v1alpha1rbac.RbacV1alpha1Client
	*v1beta1storage.StorageV1beta1Client
}

可以看到ClientSet是按包来组织Client的。

再来看下ClientSet的生成函数。NewForConfig()可以生成一个ClientSet。可以看出，在NewForConfig()中调用了各子client的生成函数，如CoreV1Client通过v1core.NewForConfig(&configShallowCopy)生成，后面的文章将以CoreV1Client为例展示ClientSet的各种操作。

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// NewForConfig creates a new Clientset for the given config.
func NewForConfig(c *restclient.Config) (*Clientset, error) {
	configShallowCopy := *c
	if configShallowCopy.RateLimiter == nil && configShallowCopy.QPS > 0 {
		configShallowCopy.RateLimiter = flowcontrol.NewTokenBucketRateLimiter(configShallowCopy.QPS, configShallowCopy.Burst)
	}
	var clientset Clientset
	var err error
	clientset.CoreV1Client, err = v1core.NewForConfig(&configShallowCopy)
	if err != nil {
		return nil, err
	}
	clientset.AppsV1beta1Client, err = v1beta1apps.NewForConfig(&configShallowCopy)
	if err != nil {
		return nil, err
	}
	clientset.AuthenticationV1beta1Client, err = v1beta1authentication.NewForConfig(&configShallowCopy)
	if err != nil {
		return nil, err
	}
	clientset.AuthorizationV1beta1Client, err = v1beta1authorization.NewForConfig(&configShallowCopy)
	if err != nil {
		return nil, err
	}
	clientset.AutoscalingV1Client, err = v1autoscaling.NewForConfig(&configShallowCopy)
	if err != nil {
		return nil, err
	}
	clientset.BatchV1Client, err = v1batch.NewForConfig(&configShallowCopy)
	if err != nil {
		return nil, err
	}
	clientset.BatchV2alpha1Client, err = v2alpha1batch.NewForConfig(&configShallowCopy)
	if err != nil {
		return nil, err
	}
	clientset.CertificatesV1alpha1Client, err = v1alpha1certificates.NewForConfig(&configShallowCopy)
	if err != nil {
		return nil, err
	}
	clientset.ExtensionsV1beta1Client, err = v1beta1extensions.NewForConfig(&configShallowCopy)
	if err != nil {
		return nil, err
	}
	clientset.PolicyV1beta1Client, err = v1beta1policy.NewForConfig(&configShallowCopy)
	if err != nil {
		return nil, err
	}
	clientset.RbacV1alpha1Client, err = v1alpha1rbac.NewForConfig(&configShallowCopy)
	if err != nil {
		return nil, err
	}
	clientset.StorageV1beta1Client, err = v1beta1storage.NewForConfig(&configShallowCopy)
	if err != nil {
		return nil, err
	}
	clientset.DiscoveryClient, err = discovery.NewDiscoveryClientForConfig(&configShallowCopy)
	if err != nil {
		glog.Errorf("failed to create the DiscoveryClient: %v", err)
		return nil, err
	}
	return &clientset, nil
}

ClientSet可以通过Core()方法获取CoreV1Client：

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//***Core()返回Core***//
func (c *Clientset) Core() v1core.CoreV1Interface {
	if c == nil {
		return nil
	}
	return c.CoreV1Client
}

CoreV1Client

CoreV1Client定义在/pkg/client/clientset_generated/release_1_5/typed/core/v1/core_client.go中，可以通过NewForConfig()返回一个CoreV1Client：

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// CoreV1Client is used to interact with features provided by the k8s.io/kubernetes/pkg/apimachinery/registered.Group group.
type CoreV1Client struct {
	restClient restclient.Interface
}
// NewForConfig creates a new CoreV1Client for the given config.
func NewForConfig(c *restclient.Config) (*CoreV1Client, error) {
	config := *c
	//***在config上设置上core v1的配置***//
	if err := setConfigDefaults(&config); err != nil {
		return nil, err
	}
	//***生成RESTClient***//
	client, err := restclient.RESTClientFor(&config)
	if err != nil {
		return nil, err
	}
	//***返回CoreV1Client***//
	return &CoreV1Client{client}, nil
}

NewForConfig()先通过setConfigDefaults()设置config，然后调用restclient.RESTClientFor()生成RESTClient，最后把RESTClient封装成CoreV1Client并返回。

setConfigDefaults()定义如下：

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//***设置coreV1Client的config***//
func setConfigDefaults(config *restclient.Config) error {
	gv, err := unversioned.ParseGroupVersion("/v1")
	if err != nil {
		return err
	}
	// if /v1 is not enabled, return an error
	if !registered.IsEnabledVersion(gv) {
		return fmt.Errorf("/v1 is not enabled")
	}
	config.APIPath = "/api"
	if config.UserAgent == "" {
		config.UserAgent = restclient.DefaultKubernetesUserAgent()
	}
	copyGroupVersion := gv
	config.GroupVersion = &copyGroupVersion
	config.NegotiatedSerializer = serializer.DirectCodecFactory{CodecFactory: api.Codecs}
	return nil
}

可以看出，setConfigDefaults()把config的APIPath字段设置为”/api”，GroupVersion字段设置为对应的gv。

CoreV1Client定义有Nodes()，Pods()，PersistentVolumes()等方法，以Pods()为例：

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func (c *CoreV1Client) Pods(namespace string) PodInterface {
	return newPods(c, namespace)
}

可以看到Pods中调用了newPods(c, namespace)生成一个pods，pods可以对”pods”资源进行各种操作。

pods

pods定义在/pkg/client/clientset_generated/release_1_5/typed/core/v1/pod.go中：

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// pods implements PodInterface
type pods struct {
	client restclient.Interface
	ns     string
}
// newPods returns a Pods
func newPods(c *CoreV1Client, namespace string) *pods {
	return &pods{
		client: c.RESTClient(),
		ns:     namespace,
	}
}

可以看到pods包含一个RESTClient和ns(即namespace)。

再来看下pods的成员方法，这些成员方法都调用了RESTClient：

Create()

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// Create takes the representation of a pod and creates it.  Returns the server's representation of the pod, and an error, if there is any.
func (c *pods) Create(pod *v1.Pod) (result *v1.Pod, err error) {
	result = &v1.Pod{}
	err = c.client.Post().
		Namespace(c.ns).
		Resource("pods").
		Body(pod).
		Do().
		Into(result)
	return
}

Update()

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// Update takes the representation of a pod and updates it. Returns the server's representation of the pod, and an error, if there is any.
func (c *pods) Update(pod *v1.Pod) (result *v1.Pod, err error) {
	result = &v1.Pod{}
	err = c.client.Put().
		Namespace(c.ns).
		Resource("pods").
		Name(pod.Name).
		Body(pod).
		Do().
		Into(result)
	return
}

Delete()

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// Delete takes name of the pod and deletes it. Returns an error if one occurs.
func (c *pods) Delete(name string, options *v1.DeleteOptions) error {
	return c.client.Delete().
		Namespace(c.ns).
		Resource("pods").
		Name(name).
		Body(options).
		Do().
		Error()
}

Get()

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// Get takes name of the pod, and returns the corresponding pod object, and an error if there is any.
func (c *pods) Get(name string) (result *v1.Pod, err error) {
	result = &v1.Pod{}
	err = c.client.Get().
		Namespace(c.ns).
		Resource("pods").
		Name(name).
		Do().
		Into(result)
	return
}

List()

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// List takes label and field selectors, and returns the list of Pods that match those selectors.
func (c *pods) List(opts v1.ListOptions) (result *v1.PodList, err error) {
	result = &v1.PodList{}
	err = c.client.Get().
		Namespace(c.ns).
		Resource("pods").
		VersionedParams(&opts, api.ParameterCodec).
		Do().
		Into(result)
	return
}

Watch()

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// Watch returns a watch.Interface that watches the requested pods.
func (c *pods) Watch(opts v1.ListOptions) (watch.Interface, error) {
	return c.client.Get().
		Prefix("watch").
		Namespace(c.ns).
		Resource("pods").
		VersionedParams(&opts, api.ParameterCodec).
		Watch()
}

Patch()

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// Patch applies the patch and returns the patched pod.
func (c *pods) Patch(name string, pt api.PatchType, data []byte, subresources ...string) (result *v1.Pod, err error) {
	result = &v1.Pod{}
	err = c.client.Patch(pt).
		Namespace(c.ns).
		Resource("pods").
		SubResource(subresources...).
		Name(name).
		Body(data).
		Do().
		Into(result)
	return
}

例子

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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)
	}
}