k8s源码学习-使用list方法获取各种资源（基于client-go）-CFANZ编程社区

初始化项目

git:(master) ✗ ls
README.md main.go
git:(master) ✗ go mod init app
go: creating new go.mod: module app
go: to add module requirements and sums:
        go mod tidy
git:(master) ✗ ls
README.md go.mod    main.go

解决项目依赖

✗ go mod tidy
go: finding module for package k8s.io/client-go/tools/clientcmd
go: finding module for package k8s.io/client-go/kubernetes
go: finding module for package k8s.io/apimachinery/pkg/apis/meta/v1
go: finding module for package k8s.io/client-go/rest
go: found k8s.io/apimachinery/pkg/apis/meta/v1 in k8s.io/apimachinery v0.23.5
go: found k8s.io/client-go/kubernetes in k8s.io/client-go v0.23.5
go: found k8s.io/client-go/rest in k8s.io/client-go v0.23.5
go: found k8s.io/client-go/tools/clientcmd in k8s.io/client-go v0.23.5

git:(master) ✗ ls
README.md go.mod    go.sum    main.go

运行代码，获取指定命名空间下的pod、deployment、daemonset等信息：

git:(master) ✗ go run main.go 
获取default namespace下的pod
nginx-deployment-9456bbbf9-78z87
nginx-deployment-9456bbbf9-7tgnm
nginx-deployment-9456bbbf9-n4mch
test-incluster-client-go
获取default namespace下的deployment的名字 
nginx-deployment
获取kube-system namespace下的daemonset的名字 
kube-proxy
获取get node的方法 
minikube
获取kube-system svc
kube-dns

代码解读：项目代码

package main

import (
  "context"
  "flag"
  "fmt"

  metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
  "k8s.io/client-go/kubernetes"
  "k8s.io/client-go/rest"
  "k8s.io/client-go/tools/clientcmd"
)

func main() {
  // 一个简单的client-go使用外部kubeconfig文件交互k8s API，这里指定minikube的config配置文件路径
  kubeconfig := flag.String("kubeconfig", "/Users/XXXX/.kube/config", "location to your kubeconfig file")
  config, err := clientcmd.BuildConfigFromFlags("", *kubeconfig)
  if err != nil {
    // handle error
    fmt.Printf("erorr %s building config from flags\n", err.Error())
    config, err = rest.InClusterConfig()
    if err != nil {
      fmt.Printf("error %s, getting inclusterconfig", err.Error())
    }
  }
  //实例化clientset对象
  clientset, err := kubernetes.NewForConfig(config)
  if err != nil {
    // handle error
    fmt.Printf("error %s, creating clientset\n", err.Error())
  }
  ctx := context.Background()
        fmt.Println("获取default namespace下的pod")

  //1、获取default下pod的名字
  pods, err := clientset.CoreV1().Pods("default").List(ctx, metav1.ListOptions{})
  if err != nil {
    // handle error
    fmt.Printf("error %s, while listing all the pods from default namespace\n", err.Error())
  }

  //在k8s源码当中https://github.com/kubernetes/kubernetes/blob/master/staging/src/k8s.io/api/core/v1/types.go
  //type PodList struct 定义了podlist ,Items []Pod定义了包含切片Pod的项目
  //metav1.TypeMeta `json:",inline"`
  // Standard list metadata.
  // More info: https://git.k8s.io/community/contributors/devel/sig-architecture/api-conventions.md#types-kinds
  // +optional
  //metav1.ListMeta `json:"metadata,omitempty" protobuf:"bytes,1,opt,name=metadata"`

  // List of pods.
  // More info: https://git.k8s.io/community/contributors/devel/sig-architecture/api-conventions.md
  //Items []Pod `json:"items" protobuf:"bytes,2,rep,name=items"`
       
  //所以我们就可以之间使用for循环取出此切片的长度了
  for _, pod := range pods.Items {
    fmt.Printf("%s\n", pod.Name)
  }

        
  fmt.Println("获取default namespace下的deployment的名字 ")
  //2、获取default下deployment的资源名字
  deployments, err := clientset.AppsV1().Deployments("default").List(ctx, metav1.ListOptions{})
  if err != nil {
                fmt.Printf("listing deployments %s\n", err.Error())
  }
  for _, d := range deployments.Items {
    fmt.Printf("%s\n", d.Name)
  }

        fmt.Println("获取kube-system namespace下的daemonset的名字 ")       
        //3、获取kube-system下daemonset的资源名字
        daemonsets, err := clientset.AppsV1().DaemonSets("kube-system").List(ctx, metav1.ListOptions{})
        if err != nil {
                fmt.Printf("listing daemonsets %s\n", err.Error())
        }
        for _, ds := range daemonsets.Items {
                fmt.Printf("%s\n", ds.Name)
        }

        fmt.Println("获取get node的方法 ")       
        //4、获取get node的的名字
        node, err := clientset.CoreV1().Nodes().List(ctx, metav1.ListOptions{})
        if err != nil {
                fmt.Printf("listing Node %s\n", err.Error())
        }
        for _, no := range node.Items {
                fmt.Printf("%s\n", no.Name)
        }

        fmt.Println("获取kube-system svc")
        //5、获取kube-system下的service
        svc, err := clientset.CoreV1().Services("kube-system").List(ctx, metav1.ListOptions{})
        if err != nil {
                fmt.Printf("listing service %s\n", err.Error())
        }
        for _, service := range svc.Items {
                fmt.Printf("%s\n", service.Name)
        }

}

开发技巧：

先找到对应的Group和Kind/resource（GR/GK）
staging/src/k8s.io/api/apps/v1/register.go 如果要开发apps资源下的deployment，先找到registor.go，找到对应的list接口

// Adds the list of known types to the given scheme.
func addKnownTypes(scheme *runtime.Scheme) error {
  scheme.AddKnownTypes(SchemeGroupVersion,
    &Deployment{},
    &DeploymentList{},
    &StatefulSet{},
    &StatefulSetList{},
    &DaemonSet{},
    &DaemonSetList{},
    &ReplicaSet{},
    &ReplicaSetList{},
    &ControllerRevision{},
    &ControllerRevisionList{},
  )
  metav1.AddToGroupVersion(scheme, SchemeGroupVersion)
  return nil
}

再去staging/src/k8s.io/api/apps/v1/types.go找到DeploymentList结构体

// DeploymentList is a list of Deployments.
type DeploymentList struct {
  metav1.TypeMeta `json:",inline"`
  // Standard list metadata.
  // +optional
  metav1.ListMeta `json:"metadata,omitempty" protobuf:"bytes,1,opt,name=metadata"`

  // Items is the list of Deployments.
  Items []Deployment `json:"items" protobuf:"bytes,2,rep,name=items"`
}

4.调用方法

deployments, err := clientset.AppsV1().Deployments("default").List(ctx, metav1.ListOptions{})

5.循环输出

for _, d := range deployments.Items {
   fmt.Printf("%s\n", d.Name)
}