kubenetes入门学习-六-Pod控制器应用进阶

原理听着好累，加油！

Pod控制器应用进阶
   资源格式清单格式：
      一级字段：apiVersion（group/version）,kind(资源类别),metadata(name,namespace,labels,annotations,.....),spec,status(只读)
      
  kubectl explain pods.spec.containers  
  kubectl explain pods.spec.containers.ports
  Pod资源：
      spec.container <[]object>
      - name
        image         镜像来源
        imagePullPolicy
           Always, Never, IfNotPresent
        ports <[]Object>
        修改镜像中的默认应用：
        command, args 
        https://kubernetes.io/docs/tasks/inject-data-application/define-command-argument-container/    
        标签：
           key=value
              key：字母、数字 _ - .     
              value: 可以为空，只能字母或者数字开头或者结尾，中间可使用              

一个资源对象上可以有多个标签，一个标签也可以添加到多个资源对象上

k8s两种标签选择器：
        等值关系  = == !=
        集合关系  
           KEY in (VALUE1,VALUE2,....)
           KEY notin (VALUE1,VALUE2,....)
           KEY 
           !key

许多资源支持内嵌字段定义其使用的标签选择器
     matchLabels:直接给定键值
     matchExpression:基于给定的表达式来定义使用的标签选择器，｛key: "KEY", operator: "OPERTOR", values: [VAL1,VAL2,...]｝
        操作符：
           In,NotIn： values字段的值必须为非空列表；
           Exists,NotExists：values字段的值必须为空列表；
nodeSelector  
     节点标签选择器
      nodeSelector：
      disktype: ssd   指定标签选择主机
      
nodeName

annotations:
    与labels不同的地方在于，它不能用于挑选资源对象，仅用于为对象提供元数据。

Pod生命周期
     状态：Pending，Running，Failed，Succeeded,Unkuown,....
     
     创建Pod：
     初始化--|----主容器启动------------------|
             |poststart---------------pre stop|
                  存活性探测
                  就绪性探测
    Pod生命周期中的重要行为：：
        初始化容器
        容器探测：
            liveness  存活性探测
            readiness 就绪性探测
    restartPolicy：
        Always, OnFailure,Never. Default to Always.
    探针类型有三种
        ExecAction、TCPSockketAction、HTTPGetAction   

    就绪性探测和service ip关系
      客户端访问直接访问service ip，service ip通过标签选择器选择后端pod执行调度。
      
    
===================================
apiVersion: v1
kind: Pod
metadata:
  name: pod-demo
  namespace: default
  labels:
    app: myapp
    tier: frontend
spec:
  containers:
  - name: myapp
    image: nginx:1.14-alpine
    imagePullPolicy: IfNotPresent   
  - name: apache
    image: httpd:2.4
    ports:
    - name: http
      containerPort:80
    - name: https
      containerPort:443
    command:
    - "/bin/sh"
    - "-c"
    - "sleep 3600"
  nodeSelector：
    disktype: ssd 
===============================
[root@master manifests]# kubectl explain pods.spec.containers
KIND:     Pod
VERSION:  v1

RESOURCE: containers <[]Object>

DESCRIPTION:
     List of containers belonging to the pod. Containers cannot currently be
     added or removed. There must be at least one container in a Pod. Cannot be
     updated.

     A single application container that you want to run within a pod.

FIELDS:
   args    <[]string>
     Arguments to the entrypoint. The docker image's CMD is used if this is not
     provided. Variable references $(VAR_NAME) are expanded using the
     container's environment. If a variable cannot be resolved, the reference in
     the input string will be unchanged. The $(VAR_NAME) syntax can be escaped
     with a double $$, ie: $$(VAR_NAME). Escaped references will never be
     expanded, regardless of whether the variable exists or not. Cannot be
     updated. More info:
     https://kubernetes.io/docs/tasks/inject-data-application/define-command-argument-container/#running-a-command-in-a-shell

   command    <[]string>
     Entrypoint array. Not executed within a shell. The docker image's
     ENTRYPOINT is used if this is not provided. Variable references $(VAR_NAME)
     are expanded using the container's environment. If a variable cannot be
     resolved, the reference in the input string will be unchanged. The
     $(VAR_NAME) syntax can be escaped with a double $$, ie: $$(VAR_NAME).
     Escaped references will never be expanded, regardless of whether the
     variable exists or not. Cannot be updated. More info:
     https://kubernetes.io/docs/tasks/inject-data-application/define-command-argument-container/#running-a-command-in-a-shell

   env    <[]Object>
     List of environment variables to set in the container. Cannot be updated.

   envFrom    <[]Object>
     List of sources to populate environment variables in the container. The
     keys defined within a source must be a C_IDENTIFIER. All invalid keys will
     be reported as an event when the container is starting. When a key exists
     in multiple sources, the value associated with the last source will take
     precedence. Values defined by an Env with a duplicate key will take
     precedence. Cannot be updated.

   image    
     Docker image name. More info:
     https://kubernetes.io/docs/concepts/containers/images This field is
     optional to allow higher level config management to default or override
     container images in workload controllers like Deployments and StatefulSets.

   imagePullPolicy    
     Image pull policy. One of Always, Never, IfNotPresent. Defaults to Always
     if :latest tag is specified, or IfNotPresent otherwise. Cannot be updated.
     More info:
     https://kubernetes.io/docs/concepts/containers/images#updating-images

   lifecycle