Kubernetes 完全教程

Agenda

1. Kubernetes 的 Pod 放置策略
   • 如何放置 Pod 到 Node
   • Affinity 以及 anti-affinity
   • Taints 和 Tolerations 机制
2. Kubernetes 应用开发
   • Java Spring Cloud 案例
   • PHP Wordpress

如何放置 Pod 到 Node — 从手动编排过度到 Kubernets

Pod 的 nodeName 和 nodeSelector 属性

kind: Pod
metadata:
name: db
spec:
containers:
- name: db
image: mysql
nodeSelector:
  disktype: ssd

内置的 node labels

kubectl get nodes --show-labels

#cloud-provider
kubernetes.io/hostname
failure-domain.beta.kubernetes.io/zone
failure-domain.beta.kubernetes.io/region
beta.kubernetes.io/instance-type
#kubelet
beta.kubernetes.io/os
beta.kubernetes.io/arch
#kubeadm
node-role.kubernetes.io/master

Affinity 以及 anti-affinity

为什么需要 Affinity 机制

1. nodeSelector 选择表达式不够强大
2. nodeSelector 不能区分强制要求和优先配置
3. 无法避免同一个应用的多个 pod 调度到同一个 node 上

Affinity

• nodeAffinity
• podAffinity
• podAntiAffinity

nodeAffinity

• preferredDuringSchedulingIgnoredDuringExecution: PreferredSchedulingTerm array
  • preference: nodeSelectorTerms
  • weight: 0-100
• requiredDuringSchedulingIgnoredDuringExecution: NodeSelector

NodeSelector

• nodeSelectorTerms
  • matchExpressions array
    • operator: In, NotIn, Exists, DoesNotExist. Gt, Lt
    • values: string array

  matchExpressions:
    - {key: disktype, operator: In, values: [ssd]}
    - {key: environment, operator: NotIn, values: [dev]}

nodeAffinity

apiVersion: v1
kind: Pod
metadata:
  name: with-node-affinity
spec:
  affinity:
    nodeAffinity:
      requiredDuringSchedulingIgnoredDuringExecution:
        nodeSelectorTerms:
        - matchExpressions:
          - key: failure-domain.beta.kubernetes.io/zone
            operator: In
            values:
            - az1
            - az2
  containers:
  - name: with-node-affinity

nodeAffinity

podAffinity/podAntiAffinity

• preferredDuringSchedulingIgnoredDuringExecution: WeightedPodAffinityTerm array
  • podAffinityTerm： PodAffinityTerm
  • weight： 0-100
• requiredDuringSchedulingIgnoredDuringExecution: PodAffinityTerm array
  • labelSelector： LabelSelector
  • namespaces： string array
  • topologyKey

podAffinity

apiVersion: v1
kind: Pod
metadata:
  name: with-pod-affinity
spec:
  affinity:
    podAffinity:
      requiredDuringSchedulingIgnoredDuringExecution:
      - labelSelector:
          matchExpressions:
          - key: security
            operator: In
            values:
            - S1
        topologyKey: failure-domain.beta.kubernetes.io/zone
  containers:
  - name: with-pod-affinity
    image: example

podAntiAffinity

apiVersion: v1
kind: Pod
metadata:
  name: zk
  lables:
    app: zk
spec:
  affinity:
    podAntiAffinity:
      requiredDuringSchedulingIgnoredDuringExecution:
        - labelSelector:
            matchExpressions:
            - key: "app"
              operator: In
              values:
              - zk
          topologyKey: "kubernetes.io/hostname"
  containers:
  - name: zk
    image: zk

为什么要有 Taints 和 Tolerations

1. Taints 隔离 Node
   • 上线新 Node 验证
   • 下线 Node 维护
   • 专用 Node
2. Tolerations Pod 对 Taints Node 的容忍
   • 表明 Pod 有资格使用专用 Node
   • 每个节点必须运行的基础 Pod

Taints 和 Tolerations

kubectl taint nodes node1 key=value:NoSchedule

• tolerations
  • operator: Exists,Equal (default)
  • effect: NoSchedule,PreferNoSchedule,NoExecute
    ```yaml
    tolerations:
• key: “key”
  operator: “Equal”
  value: “value”
  effect: “NoSchedule”
  tolerationSeconds: 3600
  ```

Tolerations

apiVersion: extensions/v1beta1
metadata:
  name: kube-proxy
spec:
  template:
    spec:
      containers:
      - name: kube-proxy
        image: gcr.io/google_containers/hyperkube-amd64:1.7.9
      tolerations:
      - key: "CriticalAddonsOnly"
        operator: "Exists"
      - key: "dedicated"
        operator: "Exists"
      - key: "node-role.kubernetes.io/master"
        effect: NoSchedule
      - key: node.cloudprovider.kubernetes.io/uninitialized
        effect: NoSchedule
        value: "true"

Taint based Evictions

kube-controller-manager --feature-gates=TaintBasedEvictions=true

内置的 taints

DaemonSet Tolerations

node.alpha.kubernetes.io/unreachable
node.kubernetes.io/not-ready

Kubernetes 应用开发案例

1. Java SpringCloud
2. PHP Wordpress

Kubernetes SpringCloud 案例

1. spring-cloud-kubernetes
2. fabric8

spring-cloud-kubernetes

https://github.com/spring-cloud-incubator/spring-cloud-kubernetes

• DiscoveryClient
• ConfigMap/Secrets PropertySource
• Pod Health Indicator
• Ribbon/Zipkin discovery

fabric8

Integrated Development Platform for Kubernetes

fabric8-maven-plugin

• fabric8:run
• fabric8:build
• fabric8:push
• fabric8:deploy

SpringCloud 案例演示

#第一次启动要翻墙
minikube start
#没开启一个新的 terminal 都需要重新执行一下
eval $(minikube docker-env)
sudo route -n add 10.0.0.0/24 $(minikube ip)

spring-cloud-kubernetes-examples

• kubernetes-hello-world-example

    mvn fabric8:run -Pkubernetes
       kubectl get service
    curl http://$clusterip
    #修改代码 重新执行上面的命令看结果

• kubernetes-reload-example

    kubectl apply -f config-map.yml
    mvn fabric8:run -Pkubernetes
    kubectl logs -f $spring-cloud-reload-podid
    kubectl edit configmap reload-example
    # 可看到修改后的 configmap 被重新加载

spring-cloud-kubernetes-examples

• kubernetes-circuitbreaker-ribbon-example

    cd name-service; mvn fabric8:run -Pkubernetes
    cd greeting-service; mvn fabric8:run -Pkubernetes
    curl $greeting-service-clusterIP/greeting
    kubectl scale --replicas=2 deployment name-service
    curl $greeting-service-clusterIP/greeting
  

PHP Wordpress

• LoadBalancer
• PersistentVolumeClaim
• Secret
• MySQL

总结

• 对 Kubernetes 的 Pod 放置策略有一个整体的了解
• 了解在 Kubernetes 上开发应用的流程以及应用如何利用 Kubernetes 的特性

作业

1. 思考自己所在公司的服务如果全部部署到 Kubernetes 中，需要如何规划 Node 的 Label，以及那些节点需要通过 taints 机制来专用，那些服务需要使用到 Affinity 机制。
2. 通过 Kubernetes 去部署一个更复杂的微服务应用（根据自己熟悉的语言来选择）

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