五、Pod控制器

1、ReplicaSet

用于弹性伸缩副本，是最基础的pod控制器

1.1简单实例

apiVersion: apps/v1
kind: ReplicaSet
metadata:
  name: base-rs-httpd
  namespace: default
  labels:
    app: web
    release: cannary
spec:
  replicas: 3
  selector:
    matchExpressions:
    - key: app
      operator: In
      values:
      - web
    - key: release
      operator: In
      values:
      - cannary
  template:
    metadata:
      labels:
        app: web
        release: cannary
    spec:
      containers:
      - name: httpd
        image: httpd:2.4
        ports:
        - name: httpd
          containerPort: 80
        imagePullPolicy: IfNotPresent
        livenessProbe:
          tcpSocket:
            port: 80
        readinessProbe:
          httpGet:
            path: /

通过标签选择器选择后端的pod
标签选择器有两种配置方式matchExpressions，matchLabels
语法格式查看kubectl explain rs.spec.selector

1.2弹性伸缩

spec:
  replicas: 3

只需要修改其replicas字段即可

1.3版本更新

    spec:
      containers:
      - name: httpd
        image: httpd:latest

只需修改其image字段即可
但是rs有一个问题，不能自动更新，所以需要用到deployment

2、Deployment

建立于ReplicaSet之上，比rs功能更加强大。可以自动更新，并且可以设置更新策略。

2.1自动更新

apiVersion: apps/v1
kind: Deployment
metadata:
  name: base-deploy-web
spec:
  replicas: 7
  selector:
    matchLabels:
      app: web-http
      release: stable
  template:
    metadata:
      labels:
        app: web-http
        release: stable
    spec:
      containers:
      - name: nginx
        image: nginx:1.18
        imagePullPolicy: IfNotPresent
        ports:
        - name: nginx
          containerPort: 80
      restartPolicy: Always

2.2基于策略自动更新

apiVersion: apps/v1
kind: Deployment
metadata:
  name: base-deploy-web
spec:
  replicas: 7
#  paused: True
  strategy:
    rollingUpdate:
      maxSurge: 10%
      maxUnavailable: 0
  selector:
    matchLabels:
      app: web-http
      release: stable
  template:
    metadata:
      labels:
        app: web-http
        release: stable
    spec:
      containers:
      - name: nginx
        image: nginx:1.18
        imagePullPolicy: IfNotPresent
        ports:
        - name: nginx
          containerPort: 80
      restartPolicy: Always

maxSurge: 代表最大用于更新时可以超过原pod的多少
maxUnavailable: 代表最大用于更新时不可提供服务的原pod为多少
可以使用数字和百分比

2.3金丝雀发布

[root@master inventory]# kubectl set image deployment base-deploy-web nginx=nginx:lastet && kubectl rollout pause deployment base-deploy-web

更新一个容器后立即暂停，当后期业务没有问题，再全部更新

3、DaemonSet

用于一个节点部署一个pod，一般用于做集群守护，日志收集，监控告警

3.1日志收集

apiVersion: apps/v1
kind: DaemonSet
metadata:
  name: fluentd-elasticsearch
  namespace: kube-system
  labels:
    k8s-app: fluentd-elasticsearch
  annntations:
spec:
  selector:
    matchLabels:
      name: fluentd-elasticsearch
  template:
    metadata:
      labels:
        name: fluentd-elasticsearch
    spec:
      containers:
      - name: fluentd-elasticsearch
        image: quay.io/fluentd_elasticsearch/fluentd:v2.5.2
        imagePullPolicy: IfNotPresent
      restartPolicy: Always

配置字段跟deployment基本相同，只是少了replicas，因为其不用于一个节点跑多个Pod