Kubernetes资源清单和Pod生命周期

资源清单

1.Kubernetes的资源清单的介绍

官网参考：https://kubernetes.io/docs/reference/generated/kubernetes-api/v1.18/#deployment-v1-apps
命令参考：
kubectl explain pod
kubectl get pod -o yaml |less

2. 自主式Pod资源清单

2.1 创建自主式Pod资源清单

[kubeadm@server1 ~]$ mkdir mainfest  创建目录存放资源清单
[kubeadm@server1 ~]$ cd mainfest/
[kubeadm@server1 mainfest]$ ls
[kubeadm@server1 mainfest]$ vim pod.yml   创建资源清单
[kubeadm@server1 mainfest]$ cat pod.yml
apiVersion: v1  指明api资源版本
kind: Pod   标记创建的资源类型
metadata:  元数据
  name: myapp  对象名称
spec:  定义目标资源的期待状态
  containers:
    - name: myapp
      image: myapp:v1  指定镜像
[kubeadm@server1 mainfest]$ kubectl create -f pod.yml
pod/myapp created
[kubeadm@server1 mainfest]$ kubectl get pod
NAME    READY   STATUS    RESTARTS   AGE
myapp   1/1     Running   0          9s
[kubeadm@server1 mainfest]$ kubectl get pod -o wide
NAME    READY   STATUS    RESTARTS   AGE     IP            NODE      NOMINATED NODE   READINESS GATES
myapp   1/1     Running   0          4m16s   10.244.1.13   server2              
[kubeadm@server1 mainfest]$ curl 10.244.1.13
Hello MyApp | Version: v1 | Pod Name

命令帮助参考：kubectl explain pod

kubectl api-versions 查看api资源属于那个群组或版本

[kubeadm@server1 mainfest]$ kubectl delete -f pod.yml ##自主式pod清单的修改需要先删除在创建
pod "myapp" deleted
[kubeadm@server1 mainfest]$ vim pod.yml
[kubeadm@server1 mainfest]$ cat pod.yml
apiVersion: v1
kind: Pod
metadata:
  name: myapp
spec:
  containers:
    - name: myapp
      image: myapp:v2  修改资源清单，此处修改的是资源镜像的版本
[kubeadm@server1 mainfest]$ kubectl create -f pod.yml
pod/myapp created
[kubeadm@server1 mainfest]$ kubectl get pod -o wide
NAME    READY   STATUS    RESTARTS   AGE   IP            NODE      NOMINATED NODE   READINESS GATES
myapp   1/1     Running   0          3s    10.244.2.14   server3              
[kubeadm@server1 mainfest]$ curl 10.244.2.14
Hello MyApp | Version: v2 | Pod Name

2.2 交互式进入pod内部

[kubeadm@server1 mainfest]$ kubectl delete -f pod.yml 
pod "myapp" deleted
[kubeadm@server1 mainfest]$ vim pod.yml 
[kubeadm@server1 mainfest]$ cat pod.yml 
apiVersion: v1
kind: Pod
metadata:
  name: myapp
spec:
  containers:
    - name: myappv1
      image: myapp:v1
    - name: demo
      image: busyboxplus
      tty: true
      stdin: true
      stdinOnce: true
[kubeadm@server1 mainfest]$ kubectl apply -f pod.yml 
pod/myapp created
[kubeadm@server1 mainfest]$ kubectl get pod
NAME    READY   STATUS    RESTARTS   AGE
myapp   2/2     Running   0          5s  ----->成功运行两个容器
[kubeadm@server1 mainfest]$ kubectl describe pod myapp 
Name:         myapp
Namespace:    default
Priority:     0
Node:         server2/172.25.1.2
Start Time:   Mon, 22 Jun 2020 20:43:54 +0800
Labels:       
Annotations:  Status:  Running
IP:           10.244.1.22    -------->这两个容器会共享网络
IPs:
  IP:  10.244.1.22
Containers:
  myappv1:
    Container ID:   docker://c3a8b858d190b68214e4bed175c27b96c202b983006ffbb0e5f1b8c3dfdc2517
    Image:          myapp:v1
    Image ID:       docker-pullable://myapp@sha256:9eeca44ba2d410e54fccc54cbe9c021802aa8b9836a0bcf3d3229354e4c8870e
    Port:           
    Host Port:      
    State:          Running
      Started:      Mon, 22 Jun 2020 20:43:55 +0800
    Ready:          True
    Restart Count:  0
    Environment:    
    Mounts:
      /var/run/secrets/kubernetes.io/serviceaccount from default-token-5qqxc (ro)
  demo:
    Container ID:   docker://7596aa40bd7d6623791038c06bacecd8169ccdff65d76609f92831f2697ce434
    Image:          busyboxplus
    Image ID:       docker-pullable://busyboxplus@sha256:ef538eae80f40015736f1ee308d74b4f38f74e978c65522ce64abdf8c8c5e0d6
    Port:           
    Host Port:      
    State:          Running
      Started:      Mon, 22 Jun 2020 20:43:55 +0800
    Ready:          True
    Restart Count:  0
    Environment:    
    Mounts:
      /var/run/secrets/kubernetes.io/serviceaccount from default-token-5qqxc (ro)
Conditions:
  Type              Status
  Initialized       True 
  Ready             True 
  ContainersReady   True 
  PodScheduled      True 
Volumes:
  default-token-5qqxc:
    Type:        Secret (a volume populated by a Secret)
    SecretName:  default-token-5qqxc
    Optional:    false
QoS Class:       BestEffort
Node-Selectors:  
Tolerations:     node.kubernetes.io/not-ready:NoExecute for 300s
                 node.kubernetes.io/unreachable:NoExecute for 300s
Events:
  Type    Reason     Age   From               Message
  ----    ------     ----  ----               -------
  Normal  Scheduled  10s   default-scheduler  Successfully assigned default/myapp to server2
  Normal  Pulled     10s   kubelet, server2   Container image "myapp:v1" already present on machine
  Normal  Created    10s   kubelet, server2   Created container myappv1
  Normal  Started    10s   kubelet, server2   Started container myappv1
  Normal  Pulling    10s   kubelet, server2   Pulling image "busyboxplus"
  Normal  Pulled     10s   kubelet, server2   Successfully pulled image "busyboxplus"
  Normal  Created    10s   kubelet, server2   Created container demo
  Normal  Started    10s   kubelet, server2   Started container demo

2.4 pod的镜像拉取策略

kubectl explain pod.spec.containers

[kubeadm@server1 mainfest]$ vim pod.yml 
[kubeadm@server1 mainfest]$ cat pod.yml 
apiVersion: v1
kind: Pod
metadata:
  name: myapp
spec:
  containers:
    - name: myappv1
      image: myapp:v1
    - name: demo
      image: busyboxplus
      tty: true
      stdin: true
      stdinOnce: true
      imagePullPolicy: IfNotPresent ------->镜像拉取时策略，需要时拉取

2.5 容器的端口映射

[kubeadm@server1 mainfest]$ vim pod.yml 
[kubeadm@server1 mainfest]$ cat pod.yml 
apiVersion: v1
kind: Pod
metadata:
  name: myapp
spec:
  containers:
    - name: myappv1
      image: myapp:v1
      ports:   ----------->此处为端口映射
      - name: http
        containerPort: 80
        hostPort: 80
[kubeadm@server1 mainfest]$ kubectl apply -f pod.yml    ------>应用这个yml
pod/myapp created
[kubeadm@server1 mainfest]$ kubectl get pod -o wide
NAME    READY   STATUS    RESTARTS   AGE   IP            NODE      NOMINATED NODE   READINESS GATES
myapp   1/1     Running   0          10s   10.244.1.23   server2              
[kubeadm@server1 mainfest]$ curl 10.244.1.23
Hello MyApp | Version: v1 | Pod Name

验证：

iptables -t nat -nL | grep 80

2.6 定义pod使用主机网络模式

定义容器使用主机网络模式会直接使用宿主机的网络，但是只能有一个不能有副本

[kubeadm@server1 mainfest]$ vim pod.yml 
[kubeadm@server1 mainfest]$ cat pod.yml 
apiVersion: v1
kind: Pod
metadata:
  name: myapp
spec:
  containers:
    - name: myappv1
      image: myapp:v1
      ports:
      - name: http
        containerPort: 80
        hostPort: 80
  hostNetwork: true  ---------->使用主机网络模式
[kubeadm@server1 mainfest]$ kubectl apply -f pod.yml 
pod/myapp created
[kubeadm@server1 mainfest]$ kubectl get pod -o wide
NAME    READY   STATUS    RESTARTS   AGE   IP           NODE      NOMINATED NODE   READINESS GATES
myapp   1/1     Running   0          4s    172.25.1.2   server2              
[kubeadm@server1 mainfest]$ curl 172.25.1.2   -------->可通过主机网络IP访问pod
Hello MyApp | Version: v1 | Pod Name

2.7 定义pod的重启策略

命令行模式

[kubeadm@server1 mainfest]$ kubectl run demo --image=busyboxplus -it --restart=Never   ----->不重启
If you don't see a command prompt, try pressing enter.
[ root@demo:/ ]$ ls
bin/     etc/     lib/     linuxrc  mnt/     proc/    run      sys/     usr/
dev/     home/    lib64    media/   opt/     root/    sbin/    tmp/     var/
[ root@demo:/ ]$ [kubeadm@server1 mainfest]$ logout  -------->退出
[root@server1 ~]# su - kubeadm 
Last login: Mon Jun 22 18:36:13 CST 2020 on pts/0
[kubeadm@server1 ~]$ kubectl get pod 
NAME   READY   STATUS      RESTARTS   AGE
demo   0/1     Completed   0          18s  ---------->退出后完成

自定义模式：

[kubeadm@server1 mainfest]$ vim pod.yml 
[kubeadm@server1 mainfest]$ cat pod.yml 
apiVersion: v1
kind: Pod
metadata:
  name: myapp
spec:
  containers:
    - name: myappv1
      image: myapp:v1
  restartPolicy: Never  ----------->不重启
[kubeadm@server1 mainfest]$ kubectl apply -f pod.yml 
pod/myapp created
[kubeadm@server1 mainfest]$ kubectl exec -it myapp -- sh
/ # nginx -s stop
2020/06/22 14:00:56 [notice] 12#12: signal process started
/ # command terminated with exit code 137
[kubeadm@server1 mainfest]$ kubectl get pod
NAME    READY   STATUS      RESTARTS   AGE
myapp   0/1     Completed   0          36s

2.8 限制pod资源

[kubeadm@server1 mainfest]$ vim pod.yml 
[kubeadm@server1 mainfest]$ cat pod.yml 
apiVersion: v1
kind: Pod
metadata:
  name: myapp
spec:
  containers:
    - name: myappv1
      image: myapp:v1
      resources:
        requests:-------->资源限制，下限（必须满足）
          memory: 100Mi
          cpu: 0.1
        limits:---------->上限（防止无限消耗资源）
          memory: 200Mi
          cpu: 0.2
[kubeadm@server1 mainfest]$ kubectl apply -f pod.yml 
pod/myapp created
[kubeadm@server1 mainfest]$ kubectl describe pod myapp 
Name:         myapp
Namespace:    default
Priority:     0
Node:         server2/172.25.1.2
Start Time:   Mon, 22 Jun 2020 22:32:49 +0800
Labels:       
Annotations:  Status:  Running
IP:           10.244.1.25
IPs:
  IP:  10.244.1.25
Containers:
  myappv1:
    Container ID:   docker://7e81871169467479581a5294c0f5094de5f01495d7e9746ad141ff30726d4776
    Image:          myapp:v1
    Image ID:       docker-pullable://myapp@sha256:9eeca44ba2d410e54fccc54cbe9c021802aa8b9836a0bcf3d3229354e4c8870e
    Port:           
    Host Port:      
    State:          Running
      Started:      Mon, 22 Jun 2020 22:32:50 +0800
    Ready:          True
    Restart Count:  0
    Limits:
      cpu:     200m
      memory:  200Mi
    Requests:
      cpu:        100m
      memory:     100Mi
    Environment:  
    Mounts:
      /var/run/secrets/kubernetes.io/serviceaccount from default-token-5qqxc (ro)
Conditions:
  Type              Status
  Initialized       True 
  Ready             True 
  ContainersReady   True 
  PodScheduled      True 
Volumes:
  default-token-5qqxc:
    Type:        Secret (a volume populated by a Secret)
    SecretName:  default-token-5qqxc
    Optional:    false
QoS Class:       Burstable
Node-Selectors:  
Tolerations:     node.kubernetes.io/not-ready:NoExecute for 300s
                 node.kubernetes.io/unreachable:NoExecute for 300s
Events:
  Type    Reason     Age   From               Message
  ----    ------     ----  ----               -------
  Normal  Scheduled  21s   default-scheduler  Successfully assigned default/myapp to server2
  Normal  Pulled     21s   kubelet, server2   Container image "myapp:v1" already present on machine
  Normal  Created    21s   kubelet, server2   Created container myappv1
  Normal  Started    21s   kubelet, server2   Started container myappv1

2.9 定义Node的label过滤标签（节点选择器）

[kubeadm@server1 mainfest]$ kubectl delete -f pod.yml 
pod "myapp" deleted
[kubeadm@server1 mainfest]$ kubectl get node --show-labels ##查看节点的标签
NAME      STATUS   ROLES    AGE     VERSION   LABELS
server1   Ready    master   3d18h   v1.18.3   beta.kubernetes.io/arch=amd64,beta.kubernetes.io/os=linux,kubernetes.io/arch=amd64,kubernetes.io/hostname=server1,kubernetes.io/os=linux,node-role.kubernetes.io/master=
server2   Ready       3d18h   v1.18.3   beta.kubernetes.io/arch=amd64,beta.kubernetes.io/os=linux,kubernetes.io/arch=amd64,kubernetes.io/hostname=server2,kubernetes.io/os=linux
server3   Ready       3d3h    v1.18.3   beta.kubernetes.io/arch=amd64,beta.kubernetes.io/os=linux,kubernetes.io/arch=amd64,kubernetes.io/hostname=server3,kubernetes.io/os=linux

[kubeadm@server1 mainfest]$ vim pod.yml 
[kubeadm@server1 mainfest]$ cat pod.yml 
apiVersion: v1
kind: Pod
metadata:
  name: myapp
spec:
  containers:
    - name: myappv1
      image: myapp:v1
      resources:
        requests:
          memory: 100Mi
          cpu: 0.1
        limits:
          memory: 200Mi
          cpu: 0.2
  nodeSelector: 
    kubernetes.io/hostname: server3  ------------->节点选择器
[kubeadm@server1 mainfest]$ kubectl apply -f pod.yml 
pod/myapp created
[kubeadm@server1 mainfest]$ kubectl get pod -o wide
NAME    READY   STATUS    RESTARTS   AGE   IP            NODE      NOMINATED NODE   READINESS GATES
myapp   1/1     Running   0          9s    10.244.2.28   server3              

2.10 定义pod的标签

$ kubectl get pod --show-labels //查看标签
$ kubectl get pod -l app //过滤包含app的标签
$ kubectl label pod demo version=v1 //打标签
$ kubectl label pod demo app=nginx --overwrite //更改标签
 

[kubeadm@server1 mainfest]$ cat pod.yml 
apiVersion: v1
kind: Pod
metadata:
  name: myapp
  labels:
    app: myapp   --------> 给pod打标签
spec:
  containers:
    - name: myappv1
      image: myapp:v1
      resources:
        requests:
          memory: 100Mi
          cpu: 0.1
        limits:
          memory: 200Mi
          cpu: 0.2
  nodeSelector: 
    kubernetes.io/hostname: server3
[kubeadm@server1 mainfest]$ kubectl apply -f pod.yml 
pod/myapp created
[kubeadm@server1 mainfest]$ kubectl get pod --show-labels 
NAME    READY   STATUS    RESTARTS   AGE   LABELS
myapp   1/1     Running   0          6s    app=myapp

[kubeadm@server1 mainfest]$ kubectl label pod myapp app=nginx --overwrite  ----->更改标签
pod/myapp labeled
[kubeadm@server1 mainfest]$ kubectl get pod --show-labels 
NAME    READY   STATUS    RESTARTS   AGE   LABELS
myapp   1/1     Running   0          74s   app=nginx

3.控制器部署pod清单

[kubeadm@server1 mainfest]$ kubectl delete -f pod.yml
pod "myapp" deleted
[kubeadm@server1 mainfest]$ vim pod2.yml
[kubeadm@server1 mainfest]$ cat pod2.yml
apiVersion: apps/v1
kind: Deployment
metadata:
  # Unique key of the Deployment instance
  name: deployment-example
spec:
  # 3 Pods should exist at all times.
  replicas: 3
  selector:
    matchLabels:
      app: nginx
  template:
    metadata:
      labels:
        # Apply this label to pods and default
        # the Deployment label selector to this value
        app: nginx
    spec:
      containers:
      - name: nginx
        # Run this image
        image: myapp:v1

[kubeadm@server1 mainfest]$ kubectl create -f pod2.yml
deployment.apps/deployment-example created
[kubeadm@server1 mainfest]$ kubectl get pod
NAME                                  READY   STATUS    RESTARTS   AGE
deployment-example-7d5c95894c-4snlm   1/1     Running   0          29s
deployment-example-7d5c95894c-88t4h   1/1     Running   0          29s
deployment-example-7d5c95894c-tlxfs   1/1     Running   0          29s
[kubeadm@server1 mainfest]$ kubectl get pod --show-labels
NAME                                  READY   STATUS    RESTARTS   AGE   LABELS
deployment-example-7d5c95894c-4snlm   1/1     Running   0          60s   app=nginx,pod-template-hash=7d5c95894c
deployment-example-7d5c95894c-88t4h   1/1     Running   0          60s   app=nginx,pod-template-hash=7d5c95894c
deployment-example-7d5c95894c-tlxfs   1/1     Running   0          60s   app=nginx,pod-template-hash=7d5c95894c
[kubeadm@server1 mainfest]$ vim pod2.yml

Pod生命周期

1.Pod 怎样管理多个容器

Pod （就像在鲸鱼荚或者豌豆荚中）是一组（一个或多个）容器容器是可移植、可执行的轻量级的镜像，镜像中包含软件及其相关依赖。（例如 Docker 容器），这些容器共享存储、网络、以及怎样运行这些容器的声明。Pod 中的内容总是并置（colocated）的并且一同调度，在共享的上下文中运行。
Pod 所建模的是特定于应用的“逻辑主机”，其中包含一个或多个应用容器，这些容器是相对紧密的耦合在一起 — 在容器出现之前，在相同的物理机或虚拟机上运行意味着在相同的逻辑主机上运行。

Pod 怎样管理多个容器：
Pod 被设计成支持形成内聚服务单元的多个协作过程（作为容器）。Pod 中的容器被自动的安排到集群中的同一物理或虚拟机上，并可以一起进行调度。容器可以共享资源和依赖、彼此通信、协调何时以及何种方式终止它们。
Pod 为其组成容器提供了两种共享资源：网络 和 存储。

网络：
每个 Pod 分配一个唯一的 IP 地址。Pod 中的每个容器共享网络命名空间，包括 IP 地址和网络端口。Pod 内的容器 可以使用 localhost 互相通信。当 Pod 中的容器与 Pod 之外 的实体通信时，它们必须协调如何使用共享的网络资源（例如端口）。存储一个 Pod 可以指定一组共享存储卷包含可被 Pod 中容器访问的数据的目录。

存储：
Pod 中的所有容器都可以访问共享卷，允许这些容器共享数据。卷还允许 Pod 中的持久数据保留下来，以防其中的容器需要重新启动。

2.Pod的生命周期

就绪检测准备好之后才可以被外部service暴露

2.1 init容器

官网参考：https://kubernetes.io/zh/docs/concepts/workloads/pods/init-containers/

Pod 可以包含多个容器，应用运行在这些容器里面，同时 Pod 也可以有一个或多个先于应用容器启动的Init 容器。

Init 容器的特点：
• 它们总是运行到完成。
• Init 容器不支持 Readiness，因为它们必须在 Pod 就绪之前运行完成。
• 每个 Init 容器必须运行成功，下一个才能够运行。

如果 Pod 的 Init 容器失败，Kubernetes 会不断地重启该 Pod，直到 Init 容 器成功为止。然而，如果 Pod 对应的 restartPolicy 值为 Never，它不会重新启动。

Init 容器的工作
因为 Init 容器具有与应用容器分离的单独镜像，其启动相关代码具有如下优势：
• Init 容器可以包含一些安装过程中应用容器中不存在的实用工具或个性化 代码。
• Init 容器可以安全地运行这些工具，避免这些工具导致应用镜像的安全性 降低。
• 应用镜像的创建者和部署者可以各自独立工作，而没有必要联合构建一个 单独的应用镜像。
• Init 容器能以不同于Pod内应用容器的文件系统视图运行。因此，Init容器 可具有访问 Secrets 的权限，而应用容器不能够访问。
• 由于 Init 容器必须在应用容器启动之前运行完成，因此 Init 容器提供了一 种机制来阻塞或延迟应用容器的启动，直到满足了一组先决条件。一旦前 置条件满足，Pod内的所有的应用容器会并行启动。

1.创建Init容器

示例一
下面的例子定义了一个具有 2 个 Init 容器的简单 Pod。 第一个等待 myservice 启动，第二个等待 mydb 启动。 一旦这两个 Init容器 都启动完成，Pod 将启动spec区域中的应用容器。

[kubeadm@server1 mainfest]$ vim init.yml
[kubeadm@server1 mainfest]$ cat init.yml
apiVersion: v1
kind: Pod
metadata:
  name: myapp-pod
  labels:
    app: myapp
spec:
  containers:
  - name: myapp-container
    image: busybox:latest
    command: ['sh', '-c', 'echo The app is running! && sleep 3600']
  initContainers:
  - name: init-myservice
    image: busybox:latest
    command: ['sh', '-c', "until nslookup myservice.default.svc.cluster.local; do echo waiting for myservice; sleep 2; done"]
  - name: init-mydb
    image: busybox:latest
    command: ['sh', '-c', "until nslookup mydb.default.svc.cluster.local; do echo waiting for mydb; sleep 2; done"]

下面的 yaml 文件展示了 mydb 和 myservice 两个 Service：

[kubeadm@server1 mainfest]$ vim service.yml
[kubeadm@server1 mainfest]$ cat service.yml
kind: Service
apiVersion: v1
metadata:
  name: myservice
spec:
  ports:
    - protocol: TCP
      port: 80
      targetPort: 9376
---
kind: Service
apiVersion: v1
metadata:
  name: mydb
spec:
  ports:
    - protocol: TCP
      port: 80
      targetPort: 9377

应用这个yml文件：

kubectl apply -f service.yml

一旦我们启动了 mydb 和 myservice 这两个 Service，我们能够看到 Init 容器完成，并且 myapp-pod 被创建，随后my-app的Pod转移进入 Running 状态

实例二：

[kubeadm@server1 mainfest]$ cat init.yml 
apiVersion: v1
kind: Pod
metadata:
  name: myapp-pod
  labels:
    app: myapp
spec:
  containers:
  - name: myapp-container
    image: myapp:v1
  initContainers:    -------------->init初始化容器
  - name: init-myservice
    image: busyboxplus
    command: ['sh', '-c', "until nslookup myservice.default.svc.cluster.local; do echo waiting for myservice; sleep 2; done"]
[kubeadm@server1 mainfest]$ kubectl apply -f init.yml 
pod/myapp-pod created
[kubeadm@server1 mainfest]$ kubectl get pod
NAME        READY   STATUS     RESTARTS   AGE
myapp-pod   0/1     Init:0/1   0          3s
[kubeadm@server1 mainfest]$ kubectl get pod
NAME        READY   STATUS     RESTARTS   AGE
myapp-pod   0/1     Init:0/1   0          5s------------------->普通容器在init初始化完成之前处于阻塞状态
[kubeadm@server1 mainfest]$ kubectl describe pod myapp-pod 
Name:         myapp-pod
Namespace:    default
Priority:     0
Node:         server3/172.25.1.3
Start Time:   Tue, 23 Jun 2020 00:18:16 +0800
Labels:       app=myapp
Annotations:  Status:  Pending
IP:           10.244.2.33
IPs:
  IP:  10.244.2.33
Init Containers:
  init-myservice:
    Container ID:  docker://b875962d0c3f6c9c116b10c4a8f0ac18985ce3cc7189abd74f62a49b71b81f16
    Image:         busyboxplus
    Image ID:      docker-pullable://busyboxplus@sha256:ef538eae80f40015736f1ee308d74b4f38f74e978c65522ce64abdf8c8c5e0d6
    Port:          
    Host Port:     
    Command:
      sh
      -c
      until nslookup myservice.default.svc.cluster.local; do echo waiting for myservice; sleep 2; done
    State:          Running  ------------------>表示初始化正在运行
      Started:      Tue, 23 Jun 2020 00:18:17 +0800
    Ready:          False
    Restart Count:  0
    Environment:    
    Mounts:
      /var/run/secrets/kubernetes.io/serviceaccount from default-token-5qqxc (ro)
Containers:
  myapp-container:
    Container ID:   
    Image:          myapp:v1
    Image ID:       
    Port:           
    Host Port:      
    State:          Waiting
      Reason:       PodInitializing
    Ready:          False
    Restart Count:  0
    Environment:    
    Mounts:
      /var/run/secrets/kubernetes.io/serviceaccount from default-token-5qqxc (ro)
Conditions:
  Type              Status
  Initialized       False 
  Ready             False 
  ContainersReady   False 
  PodScheduled      True 
Volumes:
  default-token-5qqxc:
    Type:        Secret (a volume populated by a Secret)
    SecretName:  default-token-5qqxc
    Optional:    false
QoS Class:       BestEffort
Node-Selectors:  
Tolerations:     node.kubernetes.io/not-ready:NoExecute for 300s
                 node.kubernetes.io/unreachable:NoExecute for 300s
Events:
  Type    Reason     Age   From               Message
  ----    ------     ----  ----               -------
  Normal  Scheduled  15s   default-scheduler  Successfully assigned default/myapp-pod to server3
  Normal  Pulling    14s   kubelet, server3   Pulling image "busyboxplus"
  Normal  Pulled     14s   kubelet, server3   Successfully pulled image "busyboxplus"
  Normal  Created    14s   kubelet, server3   Created container init-myservice
  Normal  Started    14s   kubelet, server3   Started container init-myservice


服务侧：
[kubeadm@server1 mainfest]$ vim service.yml 
[kubeadm@server1 mainfest]$ cat service.yml 
kind: Service
apiVersion: v1
metadata:
  name: myservice
spec:
  ports:
    - protocol: TCP
      port: 80
      targetPort: 9376
[kubeadm@server1 mainfest]$ kubectl apply -f service.yml --------->开始应用服务
service/myservice created
[kubeadm@server1 mainfest]$ kubectl get pod -w
NAME        READY   STATUS     RESTARTS   AGE
myapp-pod   0/1     Init:0/1   0          5m11s
myapp-pod   0/1     PodInitializing   0          5m19s
myapp-pod   1/1     Running           0          5m20s  ------------->初始化完成后才能运行pod

在初始化init完成之后，删除service也没有影响，因为init已经完成。

init容器完成之后，普通容器才能开始正常运行

2.2 探针

探针：
• ExecAction：在容器内执行指定命令。如果命令退出时返回码为 0 则认 为诊断成功。
• TCPSocketAction：对指定端口上的容器的 IP 地址进行 TCP 检查。如果 端口打开，则诊断被认为是成功的。
• HTTPGetAction：对指定的端口和路径上的容器的 IP 地址执行 HTTP Get 请求。如果响应的状态码大于等于200 且小于400，则诊断被认为是成功的。

探测结果:
• 成功：容器通过了诊断。
• 失败：容器未通过诊断。
• 未知：诊断失败，因此不会采取任何行动。

Kubelet 可以选择是否执行在容器上运行的三种探针执行和做出反应：
• livenessProbe：指示容器是否正在运行。如果存活探测失败，则 kubelet 会杀死容器，并且容器将受到其 重启策略 的影响。如果容器不提供存活探 针，则默认状态为 Success。

• readinessProbe：指示容器是否准备好服务请求。如果就绪探测失败，端 点控制器将从与 Pod 匹配的所有 Service 的端点中删除该 Pod 的 IP 地址。 初始延迟之前的就绪状态默认为 Failure。如果容器不提供就绪探针，则默 认状态为 Success。

• startupProbe: 指示容器中的应用是否已经启动。如果提供了启动探测 (startup probe)，则禁用所有其他探测，直到它成功为止。如果启动探测 失败，kubelet 将杀死容器，容器服从其重启策略进行重启。如果容器没有 提供启动探测，则默认状态为成功Success。

该什么时候使用存活（liveness）和就绪（readiness）探针?
如果容器中的进程能够在遇到问题或不健康的情况下自行崩溃，则不一定需要存活探针; kubelet 将根据 Pod 的restartPolicy 自动执行正确的操作。
如果希望容器在探测失败时被杀死并重新启动，那么指定一个存活探针，并指定restartPolicy 为 Always 或 OnFailure。
如果要仅在探测成功时才开始向 Pod 发送流量，请指定就绪探针。在这种情况下，就绪探针可能与存活探针相同，但是 spec 中的就绪探针的存在意味着 Pod 将在没有接收到任何流量的情况下启动，并且只有在探针探测成功后才开始接收流量。
如果希望容器能够自行维护，可以指定一个就绪探针，该探针检查与存活探针不同的端点。请注意，如果只想在 Pod 被删除时能够排除请求，则不一定需要使用就绪探针；在删除 Pod 时，Pod 会自动将自身置于未完成状态，无论就绪探针是否存在。当等待 Pod 中的容器停止时，Pod 仍处于未完成状态。

重启策略
PodSpec 中有一个 restartPolicy 字段，可能的值为 Always、OnFailure 和 Never。默认为 Always。

Pod 的生命
一般Pod 不会消失，直到人为销毁他们，这可能是一个人或控制器。
建议创建适当的控制器来创建 Pod，而不是直接自己创建 Pod。因为单独的 Pod 在机器故障的情况下没有办法自动复原，而控制器却可以。

三种可用的控制器：
• 使用 Job 运行预期会终止的 Pod，例如批量计算。Job 仅适用于重启策略 为 OnFailure 或 Never 的 Pod。
• 对预期不会终止的 Pod 使用 ReplicationController、ReplicaSet 和 Deployment ，例如 Web 服务器。 ReplicationController 仅适用于具 有 restartPolicy 为 Always 的 Pod。
• 提供特定于机器的系统服务，使用 DaemonSet 为每台机器运行一个 Pod 。

1.存活探针示例

[kubeadm@server1 mainfest]$ vim init.yml 
[kubeadm@server1 mainfest]$ cat init.yml 
apiVersion: v1
kind: Pod
metadata:
  name: myapp-pod
  labels:
    app: myapp
spec:
  containers:
  - name: myapp-container
    image: myapp:v1
  initContainers:
  - name: init-myservice
    image: busybox:1.28
    command: ['sh', '-c', "until nslookup myservice.default.svc.cluster.local; do echo waiting for myservice; sleep 2; done"]
  containers:
  - name: myapp-container
    image: myapp:v1
    imagePullPolicy: IfNotPresent
    livenessProbe:     ----------->存活探针
      tcpSocket:
        port: 80
      initialDelaySeconds: 1  -------------->container启动后延迟1s
      periodSeconds: 2    ------------------>每次探针时间间隔
      timeoutSeconds: 1   ------------------>超时时间



[kubeadm@server1 mainfest]$ cat service.yml    -------------->SVC服务用来暴露端口
kind: Service
apiVersion: v1
metadata:
  name: myservice
spec:
  ports:
    - protocol: TCP
      port: 80
      targetPort: 9376



[kubeadm@server1 mainfest]$ kubectl apply -f init.yml 
pod/myapp-pod created
[kubeadm@server1 mainfest]$ kubectl get pod
NAME        READY   STATUS     RESTARTS   AGE
myapp-pod   0/1     Init:0/1   0          3m35s
[kubeadm@server1 mainfest]$ kubectl apply -f service.yml 
service/myservice created
[kubeadm@server1 mainfest]$ kubectl get pod
NAME        READY   STATUS     RESTARTS   AGE
myapp-pod   0/1     Init:0/1   0          3m46s
[kubeadm@server1 mainfest]$ kubectl get pod
NAME        READY   STATUS     RESTARTS   AGE
myapp-pod   0/1     Init:0/1   0          3m54s
[kubeadm@server1 mainfest]$ kubectl get pod
NAME        READY   STATUS     RESTARTS   AGE
myapp-pod   0/1     Init:0/1   0          4m
[kubeadm@server1 mainfest]$ kubectl get pod
NAME        READY   STATUS    RESTARTS   AGE
myapp-pod   1/1     Running   0          4m13s
[kubeadm@server1 mainfest]$ kubectl describe pod myapp-pod
Name:         myapp-pod
Namespace:    default
Priority:     0
Node:         server3/172.25.1.3
Start Time:   Tue, 23 Jun 2020 01:09:33 +0800
Labels:       app=myapp
Annotations:  Status:  Running
IP:           10.244.2.34
IPs:
  IP:  10.244.2.34
Init Containers:
  init-myservice:
    Container ID:  docker://fc21c78635243d0e9dd380a4330707b21d4eb21d8bf42f33455d7f5c5822d312
    Image:         busybox:1.28
    Image ID:      docker-pullable://busybox@sha256:141c253bc4c3fd0a201d32dc1f493bcf3fff003b6df416dea4f41046e0f37d47
    Port:          
    Host Port:     
    Command:
      sh
      -c
      until nslookup myservice.default.svc.cluster.local; do echo waiting for myservice; sleep 2; done
    State:          Terminated
      Reason:       Completed
      Exit Code:    0
      Started:      Tue, 23 Jun 2020 01:09:51 +0800
      Finished:     Tue, 23 Jun 2020 01:13:36 +0800
    Ready:          True
    Restart Count:  0
    Environment:    
    Mounts:
      /var/run/secrets/kubernetes.io/serviceaccount from default-token-5qqxc (ro)
Containers:
  myapp-container:
    Container ID:   docker://c09ad11fdf89f84510191f3828348de203317eeabf887f2199cdb8d513990f22
    Image:          myapp:v1
    Image ID:       docker-pullable://myapp@sha256:9eeca44ba2d410e54fccc54cbe9c021802aa8b9836a0bcf3d3229354e4c8870e
    Port:           
    Host Port:      
    State:          Running
      Started:      Tue, 23 Jun 2020 01:13:36 +0800
    Ready:          True
    Restart Count:  0
    Liveness:       tcp-socket :80 delay=1s timeout=1s period=2s #success=1 #failure=3  ---------->存活探针       
    Environment:    
    Mounts:
      /var/run/secrets/kubernetes.io/serviceaccount from default-token-5qqxc (ro)
Conditions:
  Type              Status
  Initialized       True 
  Ready             True 
  ContainersReady   True 
  PodScheduled      True 
Volumes:
  default-token-5qqxc:
    Type:        Secret (a volume populated by a Secret)
    SecretName:  default-token-5qqxc
    Optional:    false
QoS Class:       BestEffort
Node-Selectors:  
Tolerations:     node.kubernetes.io/not-ready:NoExecute for 300s
                 node.kubernetes.io/unreachable:NoExecute for 300s
Events:
  Type    Reason     Age    From               Message
  ----    ------     ----   ----               -------
  Normal  Scheduled  4m38s  default-scheduler  Successfully assigned default/myapp-pod to server3
  Normal  Pulling    4m37s  kubelet, server3   Pulling image "busybox:1.28"
  Normal  Pulled     4m20s  kubelet, server3   Successfully pulled image "busybox:1.28"
  Normal  Created    4m20s  kubelet, server3   Created container init-myservice
  Normal  Started    4m20s  kubelet, server3   Started container init-myservice
  Normal  Pulled     35s    kubelet, server3   Container image "myapp:v1" already present on machine
  Normal  Created    35s    kubelet, server3   Created container myapp-container
  Normal  Started    35s    kubelet, server3   Started container myapp-container

[kubeadm@server1 mainfest]$ kubectl exec -it myapp-pod -- sh   ---------->对 myapp这个pod执行命令
/ # nginx -s stop       --------->命令内容是让nginx停止
2020/06/22 17:17:15 [notice] 12#12: signal process started
/ # command terminated with exit code 137
[kubeadm@server1 mainfest]$ kubectl get pod         ----------->查看pod的状态
NAME        READY   STATUS    RESTARTS   AGE
myapp-pod   1/1     Running   1          7m46s       --------------->有了一个restart
[kubeadm@server1 mainfest]$ kubectl exec -it myapp-pod -- sh    ------------->重复上面的步骤
/ # nginx -s stop
2020/06/22 17:17:29 [notice] 12#12: signal process started
/ # command terminated with exit code 137
[kubeadm@server1 mainfest]$ kubectl get pod
NAME        READY   STATUS             RESTARTS   AGE
myapp-pod   0/1     CrashLoopBackOff   1          8m4s
[kubeadm@server1 mainfest]$ kubectl get pod        ----------------->restart数变为2
NAME        READY   STATUS    RESTARTS   AGE
myapp-pod   1/1     Running   2          8m13s

注意：前提是restartPolicy是always

2.就绪探针示例

示例一：

[kubeadm@server1 mainfest]$ vim pod.yml 
[kubeadm@server1 mainfest]$ cat pod.yml 
apiVersion: v1
kind: Pod
metadata:
  name: myapp
  labels:
    app: myapp
spec:
  containers:
    - name: myappv1
      image: myapp:v1
      resources:
        requests:
          memory: 100Mi
          cpu: 0.1
        limits:
          memory: 200Mi
          cpu: 0.2
  nodeSelector: 
    kubernetes.io/hostname: server3
[kubeadm@server1 mainfest]$ kubectl apply -f pod.yml 
pod/myapp created
[kubeadm@server1 mainfest]$ kubectl get pod --show-labels 
NAME    READY   STATUS    RESTARTS   AGE   LABELS
myapp   1/1     Running   0          3s    app=myapp
[kubeadm@server1 mainfest]$ vim service.yml 
[kubeadm@server1 mainfest]$ cat service.yml 
kind: Service
apiVersion: v1
metadata:
  name: myservice
spec:
  ports:
    - protocol: TCP
      port: 80
      targetPort: 9376
  selector:
    app: myapp
[kubeadm@server1 mainfest]$ kubectl apply -f service.yml 
service/myservice configured
[kubeadm@server1 mainfest]$ kubectl get svc
NAME         TYPE        CLUSTER-IP       EXTERNAL-IP   PORT(S)   AGE
kubernetes   ClusterIP   10.96.0.1                443/TCP   6d23h
myservice    ClusterIP   10.110.113.147           80/TCP    3d1h
[kubeadm@server1 mainfest]$ kubectl get pod -o wide
NAME    READY   STATUS    RESTARTS   AGE   IP            NODE      NOMINATED NODE   READINESS GATES
myapp   1/1     Running   0          80s   10.244.2.37   server3              
[kubeadm@server1 mainfest]$ kubectl describe svc myservice 
Name:              myservice
Namespace:         default
Labels:            
Annotations:       Selector:  app=myapp
Type:              ClusterIP
IP:                10.110.113.147
Port:                80/TCP
TargetPort:        9376/TCP
Endpoints:         10.244.2.37:9376
Session Affinity:  None
Events:            

示例二：

[kubeadm@server1 mainfest]$ vim init.yml 
[kubeadm@server1 mainfest]$ cat init.yml 
apiVersion: v1
kind: Pod
metadata:
  name: myapp-pod
  labels:
    app: myapp
spec:
  containers:
  - name: myapp-container
    image: myapp:v1
  initContainers:
  - name: init-myservice
    image: busybox:1.28
    command: ['sh', '-c', "until nslookup myservice.default.svc.cluster.local; do echo waiting for myservice; sleep 2; done"]
  containers:
  - name: myapp-container
    image: myapp:v1
    imagePullPolicy: IfNotPresent
    livenessProbe:
      tcpSocket:
        port: 80
      initialDelaySeconds: 1
      periodSeconds: 2
      timeoutSeconds: 1
    readinessProbe:   -------------->就绪检测
      httpGet:          
        path: /hostname.html          
        port: 80        
      initialDelaySeconds: 1        
      periodSeconds: 3        
      timeoutSeconds: 1
[kubeadm@server1 mainfest]$ kubectl apply -f init.yml 
pod/myapp-pod created
[kubeadm@server1 mainfest]$ cat service.yml 
kind: Service
apiVersion: v1
metadata:
  name: myservice
spec:
  ports:
    - protocol: TCP
      port: 80
      targetPort: 9376
  selector:
    app: myapp
[kubeadm@server1 mainfest]$ kubectl apply -f service.yml 
service/myservice unchanged
[kubeadm@server1 mainfest]$ kubectl get pod
NAME        READY   STATUS    RESTARTS   AGE
myapp-pod   1/1     Running   0          32s
[kubeadm@server1 mainfest]$ kubectl exec -it myapp-pod -- sh
/ # cd /etc/nginx/conf.d/
/etc/nginx/conf.d # ls
default.conf
/etc/nginx/conf.d # vi default.conf 
/etc/nginx/conf.d # nginx -s reload   ----------->更改掉配置文件后，重新载入nginx
2020/06/25 19:22:43 [notice] 14#14: signal process started
/etc/nginx/conf.d # ps ax
PID   USER     TIME   COMMAND
    1 root       0:00 nginx: master process nginx -g daemon off;
    7 root       0:00 sh
   15 nginx      0:00 nginx: worker process
   16 root       0:00 ps ax
/etc/nginx/conf.d # [kubeadm
[kubeadm@server1 mainfest]$ kubectl get pod           
NAME        READY   STATUS    RESTARTS   AGE
myapp-pod   0/1     Running   0          4m11s            --------------->ready变为0，即就绪检测失败
[kubeadm@server1 mainfest]$ kubectl describe svc myservice 
Name:              myservice
Namespace:         default
Labels:            
Annotations:       Selector:  app=myapp
Type:              ClusterIP
IP:                10.110.113.147
Port:                80/TCP
TargetPort:        9376/TCP
Endpoints:          ------------>就绪检测没有成功之前不会加入service
Session Affinity:  None
Events:            
[kubeadm@server1 mainfest]$ kubectl get pod --show-labels 
NAME        READY   STATUS    RESTARTS   AGE     LABELS
myapp-pod   0/1     Running   0          8m46s   app=myapp  -------->虽然有标签，但是service没有主动把pod加入
[kubeadm@server1 mainfest]$ kubectl get pod -o wide
NAME        READY   STATUS    RESTARTS   AGE   IP            NODE      NOMINATED NODE   READINESS GATES
myapp-pod   0/1     Running   0          10m   10.244.1.27   server2              
[kubeadm@server1 mainfest]$ kubectl run demo --image=busyboxplus -it --restart=Never
If you don't see a command prompt, try pressing enter.
[ root@demo:/ ]$ curl 10.244.1.27
Hello MyApp | Version: v1 | Pod Name
[ root@demo:/ ]$ curl 10.244.1.27/hostname.html   --------->会访问失败



404 Not Found
nginx/1.12.2

取消注释重新加载会恢复就绪状态

[kubeadm@server1 mainfest]$ cat service.yml 
kind: Service
apiVersion: v1
metadata:
  name: myservice
spec:
  ports:
    - protocol: TCP
      port: 80
      targetPort: 80
  selector:
    app: myapp
[kubeadm@server1 mainfest]$ cat pod2.yml 
apiVersion: apps/v1
kind: Deployment
metadata:
  # Unique key of the Deployment instance
  name: deployment-example
spec:
  # 3 Pods should exist at all times.
  replicas: 2
  selector:
    matchLabels:
      app: myapp
  template:
    metadata:
      labels:
        # Apply this label to pods and default
        # the Deployment label selector to this value
        app: myapp
    spec:
      containers:
      - name: myapp
        # Run this image
        image: myapp:v2
[kubeadm@server1 mainfest]$ kubectl apply -f service.yml 
service/myservice created
[kubeadm@server1 mainfest]$ vim pod2.yml 
[kubeadm@server1 mainfest]$ kubectl apply -f pod2.yml 
deployment.apps/deployment-example unchanged
[kubeadm@server1 mainfest]$ kubectl get pod
NAME                                  READY   STATUS    RESTARTS   AGE
deployment-example-67764dd8bd-rbl7v   1/1     Running   0          5m47s
deployment-example-67764dd8bd-shwvk   1/1     Running   0          5m47s
myapp-pod                             1/1     Running   0          2m35s
[kubeadm@server1 mainfest]$ kubectl describe svc myservice 
Name:              myservice
Namespace:         default
Labels:            
Annotations:       Selector:  app=myapp
Type:              ClusterIP
IP:                10.110.155.170
Port:                80/TCP
TargetPort:        80/TCP
Endpoints:         10.244.1.28:80,10.244.2.41:80,10.244.2.43:80
Session Affinity:  None
Events:            
[kubeadm@server1 mainfest]$ kubectl run demo --image=busyboxplus -it --restart=Never
If you don't see a command prompt, try pressing enter.
[ root@demo:/ ]$ curl 10.110.155.170    --------------->即可实现负载均衡
Hello MyApp | Version: v1 | Pod Name
[ root@demo:/ ]$ curl 10.110.155.170
Hello MyApp | Version: v2 | Pod Name
[ root@demo:/ ]$ curl 10.110.155.170
Hello MyApp | Version: v2 | Pod Name
[ root@demo:/ ]$ curl 10.110.155.170
Hello MyApp | Version: v1 | Pod Name
[ root@demo:/ ]$ curl 10.110.155.170
Hello MyApp | Version: v2 | Pod Name
[ root@demo:/ ]$ curl 10.110.155.170
Hello MyApp | Version: v2 | Pod Name