Kubernetes(2) k8s资源，以及使用配置文件部署 Pod资源

本文会从资源基础定义开始讲起，在后面提供实验操作步骤。

在本章结束后应该对k8s 资源有个大概的理解，且自己手动通过模板定义的方法创建一个包括两个容器的 Pod 资源。

1 Kubernetes 中资源分类

详见 https://kubernetes.io/docs/reference/generated/kubernetes-api/v1.13/#-strong-api-overview-strong-

Workload 类型

主要用于管理且运行集群中的容器，包括：

• Container
• Cronjob
• DaemonSet
• Deployment
• Job
• Pod
• ReplicaSet
• ReplicationController
• StatefulSet

Service

该种类服务主要用于对于 Workload 资源的补充，比如提供对外服务，负载均衡。

• Service Discovery
• Load-Balance
• Ingress

Config and Storage

该种类服务主要用于在应用中注入数据，以及对容器提供外部持久化数据。

• ConfigMap
• Secret
• PersistentVolumeClaim
• StorageClass
• Volume
• VolumeAttachment
• CSI
• ...

Metadata

元数据用于配置集群内部资源行为，如：HorizontalPodAutoscaler for scaling workloads.

• PodTemplate
• LimitRange
• Event
• HorizontalPodAutoscaler(HPA)
• ...

Cluster

该资源定义了集群是如何配置的，通常是管理员权限级别的操作

• Namespace
• Node
• Role
• ClusterRole
• Persisitentvolume
• RoleBinding
• ClusterRoleBinding
• ...

2. 提取Kubernetes 资源信息

展示运行的 Pod 资源

[root@k8smaster ~]# kubectl get pod
NAME                     READY   STATUS    RESTARTS   AGE
nginx-79976cbb47-8dqnk   1/1     Running   0          3h
nginx-79976cbb47-p247g   1/1     Running   0          3h
nginx-79976cbb47-ppbqv   1/1     Running   0          3h

展示 Pod 如何配置的 （-o yaml 将输出转换为 yaml 格式）：

[root@k8smaster ~]# kubectl get pod nginx-79976cbb47-ppbqv -o yaml
apiVersion: v1
kind: Pod
metadata:
  creationTimestamp: "2019-01-03T13:34:16Z"
  generateName: nginx-79976cbb47-
  labels:
    pod-template-hash: "3553276603"
    run: nginx
  name: nginx-79976cbb47-ppbqv
  namespace: default
  ownerReferences:
  - apiVersion: apps/v1
    blockOwnerDeletion: true
    controller: true
    kind: ReplicaSet
    name: nginx-79976cbb47
    uid: 43cecba5-0f5c-11e9-8668-000c297191df
  resourceVersion: "39591"
  selfLink: /api/v1/namespaces/default/pods/nginx-79976cbb47-ppbqv
  uid: 43d50008-0f5c-11e9-8668-000c297191df
spec:
  containers:
  - image: nginx:1.14-alpine
    imagePullPolicy: IfNotPresent
    name: nginx
    ports:
    - containerPort: 80
      protocol: TCP
    resources: {}
    terminationMessagePath: /dev/termination-log
    terminationMessagePolicy: File
    volumeMounts:
    - mountPath: /var/run/secrets/kubernetes.io/serviceaccount
      name: default-token-rxs5t
      readOnly: true
  dnsPolicy: ClusterFirst
  nodeName: k8snode1
  priority: 0
  restartPolicy: Always
  schedulerName: default-scheduler
  securityContext: {}
  serviceAccount: default
  serviceAccountName: default
  terminationGracePeriodSeconds: 30
  tolerations:
  - effect: NoExecute
    key: node.kubernetes.io/not-ready
    operator: Exists
    tolerationSeconds: 300
  - effect: NoExecute
    key: node.kubernetes.io/unreachable
    operator: Exists
    tolerationSeconds: 300
  volumes:
  - name: default-token-rxs5t
    secret:
      defaultMode: 420
      secretName: default-token-rxs5t
status:
  conditions:
  - lastProbeTime: null
    lastTransitionTime: "2019-01-03T13:34:16Z"
    status: "True"
    type: Initialized
  - lastProbeTime: null
    lastTransitionTime: "2019-01-03T13:34:18Z"
    status: "True"
    type: Ready
  - lastProbeTime: null
    lastTransitionTime: null
    status: "True"
    type: ContainersReady
  - lastProbeTime: null
    lastTransitionTime: "2019-01-03T13:34:16Z"
    status: "True"
    type: PodScheduled
  containerStatuses:
  - containerID: docker://3d438e181572b2072cee7c7794914e94ee1df133d06cf32193d964c29f879525
    image: nginx:1.14-alpine
    imageID: docker-pullable://nginx@sha256:e3f77f7f4a6bb5e7820e013fa60b96602b34f5704e796cfd94b561ae73adcf96
    lastState: {}
    name: nginx
    ready: true
    restartCount: 0
    state:
      running:
        startedAt: "2019-01-03T13:34:17Z"
  hostIP: 172.16.0.12
  phase: Running
  podIP: 10.244.1.6
  qosClass: BestEffort
  startTime: "2019-01-03T13:34:16Z"

3 资源对象

通常资源对象有三种组件:

• Resource ObjectMeta: 这种信息主要描述资源的元信息比如：名字，类型，api 版本，标注，标签等。这些属性可以使用户自定义也可以是系统自动分配的
• ResourceSpec: 主要有用户自定义，描述了对系统期望的状态，且应用于创建或更新资源时
• ResourceStatus: 主要有系统自动填写，用于显示当前系统状态等信息。通常用户不需要自己手动更改

4 资源模板的格式

4.1 API 名称

• apiVersion
• kind
• spec
• metadata
• etc.

4.2 组名称

• core (by default, if it is not mentioned)
• apps
• batch
• extensions
• ...

4.3 版本号r

• v1 (stable version)
• v1beta
• ...

例如 apiVersion: v1 表示： apiVersion API 名称; group 为 core (by default); version 为 v1

5 第一级别 Attributes for K8s模板

这里是 5 种常见模板attributes, 前四个应该由用户自定义:

• apiVersion: group/version
• kind: 资源类型-如：pod, service, deployment 等.
• metadata: 元信息如：name, namespace, labels, annotations (optional)
• spec (期望状态；disired state)
• status (由 kubernetes 自动维护)

用户可使用 "kubectl explain {resource type}" 展示详细信息

例如展示 Pod 定义信息：

[root@k8smaster ~]# kubectl explain pod
KIND:     Pod
VERSION:  v1

DESCRIPTION:
     Pod is a collection of containers that can run on a host. This resource is
     created by clients and scheduled onto hosts.

FIELDS:
   apiVersion    <string>
     APIVersion defines the versioned schema of this representation of an
     object. Servers should convert recognized schemas to the latest internal
     value, and may reject unrecognized values. More info:
     https://git.k8s.io/community/contributors/devel/api-conventions.md#resources

   kind    <string>
     Kind is a string value representing the REST resource this object
     represents. Servers may infer this from the endpoint the client submits
     requests to. Cannot be updated. In CamelCase. More info:
     https://git.k8s.io/community/contributors/devel/api-conventions.md#types-kinds

   metadata