紧接k8s client-go 源码分析(一)
2.6 RestClient
RESTClient对象的创建同样是以来传入的config信息。
client, err := rest.RESTClientForConfigAndClient(&config, h)
2.6.1 RESTClientForConfigAndClient
// RESTClientForConfigAndClient returns a RESTClient that satisfies the requested attributes on a
// client Config object.
// Unlike RESTClientFor, RESTClientForConfigAndClient allows to pass an http.Client that is shared
// between all the API Groups and Versions.
// Note that the http client takes precedence over the transport values configured.
// The http client defaults to the `http.DefaultClient` if nil.
func RESTClientForConfigAndClient(config *Config, httpClient *http.Client) (*RESTClient, error) {
if config.GroupVersion == nil {
return nil, fmt.Errorf("GroupVersion is required when initializing a RESTClient")
}
if config.NegotiatedSerializer == nil {
return nil, fmt.Errorf("NegotiatedSerializer is required when initializing a RESTClient")
}
baseURL, versionedAPIPath, err := defaultServerUrlFor(config)
if err != nil {
return nil, err
}
rateLimiter := config.RateLimiter
if rateLimiter == nil {
qps := config.QPS
if config.QPS == 0.0 {
qps = DefaultQPS
}
burst := config.Burst
if config.Burst == 0 {
burst = DefaultBurst
}
if qps > 0 {
rateLimiter = flowcontrol.NewTokenBucketRateLimiter(qps, burst)
}
}
var gv schema.GroupVersion
if config.GroupVersion != nil {
gv = *config.GroupVersion
}
clientContent := ClientContentConfig{
AcceptContentTypes: config.AcceptContentTypes,
ContentType: config.ContentType,
GroupVersion: gv,
Negotiator: runtime.NewClientNegotiator(config.NegotiatedSerializer, gv),
}
restClient, err := NewRESTClient(baseURL, versionedAPIPath, clientContent, rateLimiter, httpClient)
if err == nil && config.WarningHandler != nil {
restClient.warningHandler = config.WarningHandler
}
return restClient, err
}
RESTClientForConfigAndClient中调用NewRESTClient创建RESTClient
2.6.2 NewRESTClient
// NewRESTClient creates a new RESTClient. This client performs generic REST functions
// such as Get, Put, Post, and Delete on specified paths.
func NewRESTClient(baseURL *url.URL, versionedAPIPath string, config ClientContentConfig, rateLimiter flowcontrol.RateLimiter, client *http.Client) (*RESTClient, error) {
if len(config.ContentType) == 0 {
config.ContentType = "application/json"
}
base := *baseURL
if !strings.HasSuffix(base.Path, "/") {
base.Path += "/"
}
base.RawQuery = ""
base.Fragment = ""
return &RESTClient{
base: &base,
versionedAPIPath: versionedAPIPath,
content: config,
createBackoffMgr: readExpBackoffConfig,
rateLimiter: rateLimiter,
Client: client,
}, nil
}
2.6.3 RESTClient结构体
RESTClient是整个clientset的核心数据，RESTClient结构体中包含了http.Client，即本质上RESTClient就是一个http.Client的封装实现。
// RESTClient imposes common Kubernetes API conventions on a set of resource paths.
// The baseURL is expected to point to an HTTP or HTTPS path that is the parent
// of one or more resources. The server should return a decodable API resource
// object, or an api.Status object which contains information about the reason for
// any failure.
//
// Most consumers should use client.New() to get a Kubernetes API client.
type RESTClient struct {
// base is the root URL for all invocations of the client
base *url.URL
// versionedAPIPath is a path segment connecting the base URL to the resource root
versionedAPIPath string
// content describes how a RESTClient encodes and decodes responses.
content ClientContentConfig
// creates BackoffManager that is passed to requests.
createBackoffMgr func() BackoffManager
// rateLimiter is shared among all requests created by this client unless specifically
// overridden.
rateLimiter flowcontrol.RateLimiter
// warningHandler is shared among all requests created by this client.
// If not set, defaultWarningHandler is used.
warningHandler WarningHandler
// Set specific behavior of the client. If not set http.DefaultClient will be used.
Client *http.Client
}
2.6.4 RESTClient.Interface接口
// Interface captures the set of operations for generically interacting with Kubernetes REST apis.
type Interface interface {
GetRateLimiter() flowcontrol.RateLimiter
Verb(verb string) *Request
Post() *Request
Put() *Request
Patch(pt types.PatchType) *Request
Get() *Request
Delete() *Request
APIVersion() schema.GroupVersion
}
RESTClient.Interface中Post、Put、Get、Delete时，实际上调用Verb(verb string)函数
// Verb sets the verb this request will use.
func (r *Request) Verb(verb string) *Request {
r.verb = verb
return r
}
以List为例
func (c *pods) List(ctx context.Context, opts metav1.ListOptions) (result *v1.PodList, err error) {
var timeout time.Duration
if opts.TimeoutSeconds != nil {
timeout = time.Duration(*opts.TimeoutSeconds) * time.Second
}
result = &v1.PodList{}
err = c.client.Get().
Namespace(c.ns).
Resource("pods").
VersionedParams(&opts, scheme.ParameterCodec).
Timeout(timeout).
Do(ctx).
Into(result)
return
}
Verb函数返回一个填充verb字段的Request, 最后调用Do()方法实现一个http请求获取Result。
2.7 总结
client-go对k8s资源对象的调用，先获取k8s的配置信息，链接对配置上节点的apiserver。
整个调用过程如下： kubeconfig -> rest.config -> clientset -> 具体的client(CoreV1Client)->具体资源对象(pod)->RESTClient -> http.Client -> HTTP请求的发送即响应。 clientset中不同的client和client中不同的资源对象方法实现对k8s资源对象的增删改查，常见的client有CoreV1Client、AppV1beta1Client等。
3. client-go对k8s资源的调用
创建clientset
//获取kubeconfig
kubeconfig = flag.String("kubeconfig", filepath.Join(home, ".kube", "config"), "(optional) absolute path to the kubeconfig file")
//创建config
config, err := clientcmd.BuildConfigFromFlags("", *kubeconfig)
//创建clientset
clientset, err := kubernetes.NewForConfig(config)
//具体的资源调用见以下例子
3.1 deployment
//声明deployment对象\
var deployment *v1beta1.Deployment\
//构造deployment对象\
//创建deployment\
deployment, err := clientset.AppsV1beta1().Deployments(<namespace>).Create(<deployment>)\
//更新deployment\
deployment, err := clientset.AppsV1beta1().Deployments(<namespace>).Update(<deployment>)\
//删除deployment\
err := clientset.AppsV1beta1().Deployments(<namespace>).Delete(<deployment.Name>, &meta_v1.DeleteOptions{})\
//查询deployment\
deployment, err := clientset.AppsV1beta1().Deployments(<namespace>).Get(<deployment.Name>, &meta_v1.GetOptions{})\
//列出deployment\
deploymentList, err := clientset.AppsV1beta1().Deployments(<namespace>).List(&meta_v1.ListOptions{})\
//watch deployment\
watchInterface, err := clientset.AppsV1beta1().Deployments(<namespace>).Watch(&meta_v1.ListOptions{})\
3.2 service
//声明service对象
var service *v1.Service
//构造service对象
//创建service
service, err := clientset.CoreV1().Services(<namespace>).Create(<service>)
//更新service
service, err := clientset.CoreV1().Services(<namespace>).Update(<service>)
//删除service
err := clientset.CoreV1().Services(<namespace>).Delete(<service.Name>, &meta_v1.DeleteOptions{})
//查询service
service, err := clientset.CoreV1().Services(<namespace>).Get(<service.Name>, &meta_v1.GetOptions{})
//列出service
serviceList, err := clientset.CoreV1().Services(<namespace>).List(&meta_v1.ListOptions{})
//watch service
watchInterface, err := clientset.CoreV1().Services(<namespace>).Watch(&meta_v1.ListOptions{})
4. client-go所用到的设计模式（后续补充）
4.1 建造者模式
type Request struct {
c *RESTClient
warningHandler WarningHandler
rateLimiter flowcontrol.RateLimiter
backoff BackoffManager
timeout time.Duration
// generic components accessible via method setters
verb string
pathPrefix string
subpath string
params url.Values
headers http.Header
// structural elements of the request that are part of the Kubernetes API conventions
namespace string
namespaceSet bool
resource string
resourceName string
subresource string
// output
err error
body io.Reader
retry WithRetry
}
// List takes label and field selectors, and returns the list of Pods that match those selectors.
func (c *pods) List(ctx context.Context, opts metav1.ListOptions) (result *v1.PodList, err error) {
var timeout time.Duration
if opts.TimeoutSeconds != nil {
timeout = time.Duration(*opts.TimeoutSeconds) * time.Second
}
result = &v1.PodList{}
err = c.client.Get().
Namespace(c.ns).
Resource("pods").
VersionedParams(&opts, scheme.ParameterCodec).
Timeout(timeout).
Do(ctx).
Into(result)
return
}
