Kubernetes API相关知识

Kubernetes集群中，所有组件需要操作集群资源时都通过调用kube-apiserver提供的RESTful接口来实现。kube-apiserver进一步和etcd交互，完成资源信息的更新。
Kubernetes中的资源本质上是一个API对象，这个对象的期望状态被APIServer保存在etcd中，然后提供RESTful接口用于更新这些对象。
与kube-apiserver的交互方式可以是直接交互，也可以是通过kubectl或client-go的方式。

准备工作

使用kind准备一个Kubernetes集群

Curl方式访问API

准备工作

kube-apiserver提供的是双向TLS认证的HTTPS服务，所以这里xshell开启一个命令行窗口，通过kubectl代理暴露API Server服务

[root@test ~]# kubectl proxy --port=8080
Starting to serve on 127.0.0.1:8080

在另一个命令行窗口进行测试

[root@test ~]# curl localhost:8080/version
{
  "major": "1",
  "minor": "21",
  "gitVersion": "v1.21.14",
  "gitCommit": "0f77da5bd4809927e15d1658fb4aa8f13ad890a5",
  "gitTreeState": "clean",
  "buildDate": "2022-10-26T15:31:07Z",
  "goVersion": "go1.16.15",
  "compiler": "gc",
  "platform": "linux/amd64"
}

创建nginx-deploy.yaml

apiVersion: apps/v1
kind: Deployment
metadata:
  name: nginx-deploy
  namespace: default
spec:
  replicas: 3
  selector:
    matchLabels:
      app: nginx
  template:
    metadata:
      labels:
        app: nginx
    spec:
      containers:
        - name: nginx
          image: nginx:1.14.2
          ports:
            - containerPort: 80

资源创建

curl执行命令

curl -X POST -H \
'Content-Type: application/yaml' \
--data-binary '@nginx-deploy.yaml' \
http://localhost:8080/apis/apps/v1/namespaces/default/deployments

返回参数

{
  "kind": "Deployment",
  "apiVersion": "apps/v1",
  "metadata": {
    "name": "nginx-deploy",
    "namespace": "default",
    "uid": "d6cf96bb-c831-4efd-9e30-3983edb4ceb4",
    "resourceVersion": "1347583",
    "generation": 1,
    "creationTimestamp": "2023-04-15T10:00:41Z",
    "managedFields": [
      {
        "manager": "curl",
        "operation": "Update",
        "apiVersion": "apps/v1",
        "time": "2023-04-15T10:00:41Z",
        "fieldsType": "FieldsV1",
        "fieldsV1": {"f:spec":{"f:progressDeadlineSeconds":{},"f:replicas":{},"f:revisionHistoryLimit":{},"f:selector":{},"f:strategy":{"f:rollingUpdate":{".":{},"f:maxSurge":{},"f:maxUnavailable":{}},"f:type":{}},"f:template":{"f:metadata":{"f:labels":{".":{},"f:app":{}}},"f:spec":{"f:containers":{"k:{\"name\":\"nginx\"}":{".":{},"f:image":{},"f:imagePullPolicy":{},"f:name":{},"f:ports":{".":{},"k:{\"containerPort\":80,\"protocol\":\"TCP\"}":{".":{},"f:containerPort":{},"f:protocol":{}}},"f:resources":{},"f:terminationMessagePath":{},"f:terminationMessagePolicy":{}}},"f:dnsPolicy":{},"f:restartPolicy":{},"f:schedulerName":{},"f:securityContext":{},"f:terminationGracePeriodSeconds":{}}}}}
      }
    ]
  },
  "spec": {
    "replicas": 3,
    "selector": {
      "matchLabels": {
        "app": "nginx"
      }
    },
    "template": {
      "metadata": {
        "creationTimestamp": null,
        "labels": {
          "app": "nginx"
        }
      },
      "spec": {
        "containers": [
          {
            "name": "nginx",
            "image": "nginx:1.14.2",
            "ports": [
              {
                "containerPort": 80,
                "protocol": "TCP"
              }
            ],
            "resources": {
              
            },
            "terminationMessagePath": "/dev/termination-log",
            "terminationMessagePolicy": "File",
            "imagePullPolicy": "IfNotPresent"
          }
        ],
        "restartPolicy": "Always",
        "terminationGracePeriodSeconds": 30,
        "dnsPolicy": "ClusterFirst",
        "securityContext": {
          
        },
        "schedulerName": "default-scheduler"
      }
    },
    "strategy": {
      "type": "RollingUpdate",
      "rollingUpdate": {
        "maxUnavailable": "25%",
        "maxSurge": "25%"
      }
    },
    "revisionHistoryLimit": 10,
    "progressDeadlineSeconds": 600
  },
  "status": {
    
  }
}

查看资源对象，已成功创建

[root@test ch3]# kubectl get deploy
NAME           READY   UP-TO-DATE   AVAILABLE   AGE
nginx-deploy   3/3     3            3           2m15s

资源删除

curl执行命令

curl -X DELETE -H 'Content-Type: application/yaml' \
--data 'gracePeriodSeconds:0 orphanDependents: false' \
http://localhost:8080/apis/apps/v1/namespaces/default/deployments/nginx-deploy

返回参数

{
  "kind": "Status",
  "apiVersion": "v1",
  "metadata": {
    
  },
  "status": "Success",
  "details": {
    "name": "nginx-deploy",
    "group": "apps",
    "kind": "deployments",
    "uid": "d6cf96bb-c831-4efd-9e30-3983edb4ceb4"
  }
}

查看资源对象，已成功删除

[root@test ch3]# kubectl get deploy
No resources found in default namespace.

kubectl raw方式访问API

kubectl raw方式默认使用kubeconfig中的连接信息

[root@test ch3]# kubectl get --raw /version
{
  "major": "1",
  "minor": "21",
  "gitVersion": "v1.21.14",
  "gitCommit": "0f77da5bd4809927e15d1658fb4aa8f13ad890a5",
  "gitTreeState": "clean",
  "buildDate": "2022-10-26T15:31:07Z",
  "goVersion": "go1.16.15",
  "compiler": "gc",
  "platform": "linux/amd64"
}

资源查询

查询Pod信息

kubectl get --raw /apis/apps/v1/namespaces/default/deployments/nginx-deploy

GV & GVK & GVR

• GV: API Group & Version
  • API Group 是相关 API 功能的集合
  • 每个 Group 拥有一或多个 Versions
• GVK: Group Version Kind
  • 每个 GV 都包含 N 个 api 类型，称之为 Kinds，不同 Version 同一个 Kinds 可能不同
• GVR: Group Version Resource
  • Resource 是 Kind 的对象标识，一般来 Kind 和 Resource 是 1:1 的，但是有时候存在 1:n 的关系，不过对于 Operator 来说都是 1:1 的关系

举例说明：

apiVersion: apps/v1 # 这个是 GV，G 是 apps，V 是 v1
kind: Deployment    # 这个就是 Kind
sepc:               # 加上下放的 spec 就是 Resource了
  ...

根据 GVK K8s 就能找到你到底要创建什么类型的资源，根据你定义的 Spec 创建好资源之后就成为了 Resource，也就是 GVR。GVK/GVR 就是 K8s 资源的坐标，是创建/删除/修改/读取资源的基础