将多个容器部署在一个pod里一个pod运行多个容器

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信息小飞侠 2024-03-19 22:26:52

文章标签 将多个容器部署在一个pod里 kubernetes docker 容器 Pod 文章分类 云原生云计算

Pod基本概念

Pod是Kubernetes创建和管理的最小单元，一个Pod由一个容器或多个容器组成，这些容器共享存储、网络。

Pod特点

.一个Pod可以理解为是一个应用实例，提供服务.
Pod中容器始终部署在一个Node上
Pod中容器共享网络、存储资源
Kubernetes直接管理Pod，而不是容器

Pod存在意义

Pod主要用法:

·运行单个容器:最常见的用法，在这种情况下，可以将Pod看做是单个容器的抽象封装
运行多个容器:封装多个紧密耦合且需要共享资源的应用程序

如果有这些需求，你可以运行多个容器:

两个应用之间发生文件交互
两个应用需要通过127.0.0.1或者socket通信
两个应用需要发生频繁的调用

Pod资源共享实现机制

Pod管理命令

//创建Pod:
kubectl apply -f pod.yaml
或者使用命令kubectl run nginx --image=nginx

//查看Pod:
kubectl get pods
kubectl describe pod <Pod名称>

//查看日志:
kubectl logs <Pod名称>[-c CONTAINER]
kubectl logs <Pod名称>[-c CONTAINER] -f

//进入容器终端:
kubectl exec <Pod名称> [-c CONTAINER] -- bash

//删除pod
kubectl delete <Pod名称>
//定义Pod
apiVersion: v1
kind: Pod
metadata:
  name: my-podspec:
containers:
- name: container1
  image: nginx
- name: container2
  image: centos

重启策略

Always：当容器终止退出后，总是重启容器，默认策略（总是重启）
OnFailure：当容器异常退出(退出状态码非0)时，才重启容器 （非正常退出，比如stop、kill）
Never：当容器终止退出，从不重启容器（永不重启）

[root@master ~]# kubectl explain pod.spec.restartPolicy
KIND:     Pod
VERSION:  v1

FIELD:    restartPolicy <string>

DESCRIPTION:
     Restart policy for all containers within the pod. One of Always, OnFailure,
     Never. Default to Always. More info:
     https://kubernetes.io/docs/concepts/workloads/pods/pod-lifecycle/#restart-policy

//修改为Never
[root@master ~]# cat test.yml 
apiVersion: v1
kind: Pod
metadata: 
  name: web
spec: 
  containers:
  - name: nginx
    image: nginx
    imagePullPolicy: IfNotPresent
  - name: test
    image: busybox
    imagePullPolicy: IfNotPresent
    command: ["bin/sh","-c","sleep 45"]
  restartPolicy: Never 		#默认的话不用修改，改为never后停止容器不会重启
 
[root@master ~]# kubectl apply -f test.yml 
pod/web created
[root@master ~]# kubectl get pod
NAME   READY   STATUS    RESTARTS   AGE
web    2/2     Running   0          18s
[root@master ~]#  kubectl get pod -o wide -w		#-w实时监控，在node2上面用docker命令关上其中一个，发现不会重启
NAME   READY   STATUS    RESTARTS   AGE   IP            NODE    NOMINATED NODE   READINESS GATES
web    2/2     Running   0          35s   10.244.1.25   node1   <none>           <none>
web    1/2     NotReady   0          49s   10.244.1.25   node1   <none>           <none>


//修改为Always
[root@master ~]# cat test.yml 
apiVersion: v1
kind: Pod
metadata: 
  name: web
spec: 
  containers:
  - name: nginx
    image: nginx
    imagePullPolicy: IfNotPresent
  - name: test
    image: busybox
    imagePullPolicy: IfNotPresent
    command: ["bin/sh","-c","sleep 45"]
  restartPolicy: Always 

//删除原来的test.yml ,重启启动一个新的pod
[root@master ~]# kubectl delete -f test.yml 
pod "web" deleted
[root@master ~]# kubectl apply -f test.yml 
pod/web created

//启动好后,在node1上停止test
[root@master ~]#  kubectl get pods -o wide -w
NAME   READY   STATUS    RESTARTS   AGE   IP            NODE    NOMINATED NODE   READINESS GATES
web    2/2     Running   0          6s    10.244.1.25   node1   <none>           <none>
web    1/2     NotReady   0          46s   10.244.1.25   node1   <none>           <none>
web    2/2     Running    1          47s   10.244.1.25   node1   <none>           <none>
web    1/2     NotReady   1          92s   10.244.1.25   node1   <none>           <none>
web    1/2     CrashLoopBackOff   1          102s   10.244.1.25   node1   <none>           <none>
web    2/2     Running            2          103s   10.244.1.25   node1   <none>           <none>
等待一定的时间后重启，而后自动起一台新的

//OnFailure
[root@master ~]# cat test.yml 
apiVersion: v1
kind: Pod
metadata: 
  name: web
spec: 
  containers:
  - name: nginx
    image: nginx
    imagePullPolicy: IfNotPresent
  - name: test
    image: busybox
    imagePullPolicy: IfNotPresent
    command: ["bin/sh","-c","sleep 45"]
  restartPolicy: OnFailure 

//删除原来的test.yml ,重启启动一个新的pod
[root@master ~]# kubectl delete -f test.yml 
pod "web" deleted
[root@master ~]# kubectl apply -f test.yml 
pod/web created




[root@master ~]# kubectl get pods -o wide -w
NAME   READY   STATUS              RESTARTS   AGE   IP       NODE    NOMINATED NODE   READINESS GATES
web    2/2     Running             0          5s    10.244.1.62   node1   <none>           <none>
web    1/2     Error               0          32s   10.244.1.62   node1   <none>           <none>
//异常退出（手动杀掉）
web    2/2     Running             1          38s   10.244.1.62   node1   <none>           <none>
//正常退出（60秒）
web    1/2     NotReady            1          99s   10.244.1.62   node1   <none>           <none>
web    1/2     NotReady            1          2m26s   10.244.1.62   node1   <none>           <none>

健康检查

livenessProbe(存活检查)︰如果检查失败，将杀死容器，根据Pod的restartPolicy来操作
readinessProbe(就绪检查)︰如果检查失败，Kubernetes会把Pod从service endpoints中剔除

支持的检查方式:

httpGet:发送HTTP请求，返回200-400范围状态码为成功
exec: 执行hell命令返回状态码是0为成功
tcpSocket:发起TCP Socket建立成功
与重启策略相结合使用

重启策略+健康检查(应用自修复)

将多个容器部署在一个pod里一个pod运行多个容器_Pod

//端口探测
[root@master ~]# cat test.yml 
---
apiVersion: v1
kind: Pod
metadata:
  name: web
spec:
  containers:
  - name: nginx
    image: nginx
    imagePullPolicy: IfNotPresent
    ports:
    - containerPort: 80
      hostPort: 80
    livenessProbe:
      tcpSocket:
        port: 80
      initialDelaySeconds: 20 		#启动容器后多少秒健康检查
      periodSeconds: 10 			#以后间隔多少秒检查一次
    readinessProbe:
      httpGet:
        port: 80
      initialDelaySeconds: 20
      periodSeconds: 10


[root@master ~]# kubectl apply -f test.yml 
pod/web created

//查看pod,发现在进行初始化
[root@master ~]# kubectl get pod
NAME   READY（就绪状态）   STATUS（存活状态）    RESTARTS   AGE
web    0/1     Running   0          22s

//等待一定时间后会进入运行
[root@master ~]# kubectl get pod
NAME   READY   STATUS    RESTARTS   AGE
web    1/1     Running   0          26s
如果失败init容器默认会在State中显示CrashLoopBackOff (重启/异常)
在Reason会显示Error
State 代表状态
Reason 原因
Terminated 终止
Completed 完成

环境变量

变量值几种定义方式：

自定义变量值
变量值从Pod属性获取
变量值从Secrt，ConfigMap

[root@master ~]# kubectl explain pod.spec.containers.env.valueFrom 
KIND:     Pod
VERSION:  v1

RESOURCE: valueFrom <Object>

DESCRIPTION:
     Source for the environment variable's value. Cannot be used if value is not
     empty.

     EnvVarSource represents a source for the value of an EnvVar.

FIELDS:
   configMapKeyRef      <Object>
     Selects a key of a ConfigMap.

   fieldRef     <Object>
     Selects a field of the pod: supports metadata.name, metadata.namespace,
     `metadata.labels['<KEY>']`, `metadata.annotations['<KEY>']`, spec.nodeName,
     spec.serviceAccountName, status.hostIP, status.podIP, status.podIPs.

   resourceFieldRef     <Object>
     Selects a resource of the container: only resources limits and requests
     (limits.cpu, limits.memory, limits.ephemeral-storage, requests.cpu,
     requests.memory and requests.ephemeral-storage) are currently supported.

   secretKeyRef <Object>
     Selects a key of a secret in the pod's namespace

第一种

---
apiVersion: v1
kind: Pod
metadata:
  name: test
spec:
  containers:
  - name: bi
    image: busybox
    imagePullPolicy: IfNotPresent
    command: ["bin/sh","-c","sleep 45"]
    env:
    - name: HN
      value: tom

[root@master ~]# kubectl apply -f test.yml 
pod/test created
[root@master ~]# kubectl get pod
NAME   READY   STATUS    RESTARTS   AGE
test   1/1     Running   0          33s
[root@master ~]# kubectl exec -it test -- /bin/sh
/ # echo $HN
tom

第二种

[root@master ~]# cat test.yml 
---
apiVersion: v1
kind: Pod
metadata:
  name: test
spec:
  containers:
  - name: bi
    image: busybox
    imagePullPolicy: IfNotPresent
    command: ["bin/sh","-c","sleep 45"]
    env:
    - name: HN
      valueFrom:
        fieldRef:
          fieldPath: metadata.name
          
[root@master ~]# kubectl delete -f test.yml 
pod "test" deleted
[root@master ~]# kubectl apply -f test.yml 
pod/test created
[root@master ~]# kubectl get pod
NAME   READY   STATUS    RESTARTS   AGE
test   1/1     Running   0          24s
[root@master ~]# kubectl exec -it test -- /bin/sh
/ # echo $HN
test

第三种

[root@master ~]# cat test.yml 
---
apiVersion: v1
kind: Pod
metadata:
  name: test
spec:
  containers:
  - name: bi
    image: busybox
    imagePullPolicy: IfNotPresent
    command: ["bin/sh","-c","sleep 45"]
    env:
    - name: HN
      valueFrom:
        fieldRef:
          fieldPath: spec.nodeName

[root@master ~]# kubectl delete -f test.yml 
pod "test" deleted
[root@master ~]# kubectl apply -f test.yml 
pod/test created

[root@master ~]# kubectl get pod
NAME   READY   STATUS    RESTARTS   AGE
test   1/1     Running   0          33s
[root@master ~]# kubectl exec -it test -- /bin/sh
/ #  echo $HN
node1

第四种

[root@master ~]# cat test.yml 
---
apiVersion: v1
kind: Pod
metadata:
  name: test
spec:
  containers:
  - name: bi
    image: busybox
    imagePullPolicy: IfNotPresent
    command: ["bin/sh","-c","sleep 45"]
    env:
    - name: HN
      valueFrom:
        fieldRef:
          fieldPath: status.podIP

[root@master ~]# kubectl delete -f test.yml 
pod "test" deleted
[root@master ~]# kubectl apply -f test.yml 
pod/test created
[root@master ~]# kubectl exec -it test -- /bin/sh
/ # echo $HN
10.244.1.75
/ # exit
[root@master ~]# kubectl get pod -o wide
NAME   READY   STATUS    RESTARTS   AGE   IP            NODE    NOMINATED NODE   READINESS GATES
test   1/1     Running   1          50s   10.244.1.75   node1   <none>           <none>

init Container(初始化容器)

初始化容器

Init Container:用于初始化工作，执行完就结束(一次性任务)
支持大部分应用容器配置，但不支持健康检查
优先应用容器执行

应用场景:

环境检查:例如确保应用容器依赖的服务启动后再启动应用容器
初始化配置:例如给应用容器准备配置文件

示例
这里部署一个web网站,网站程序没有打到镜像中，而是希望从代码仓库中动态拉取放到应用容器中

在这里插入代码片[root@master ~]# cat test.yml 
---
apiVersion: v1
kind: Pod
metadata:
  name: web
  namespace: default
spec:
  initContainers:
  - name: download
    image: busybox
    imagePullPolicy: IfNotPresent
    volumeMounts:
    - name: data
      mountPath: /tmp
  containers:
  - name: nginx
    image: nginx
    imagePullPolicy: IfNotPresent
    ports:
    - containerPort: 80
      hostPort: 80
    volumeMounts:
    - name: data
      mountPath: /usr/share/nginx/html
  volumes:
  - name: data
    hostPath:
      path: /var/www/html


//不管在哪个节点我都创建
[root@node1 ~]# mkdir /var/www/html/ -p
[root@node1 ~]# cd /var/www/html/
[root@node1 html]# echo  "node1" > index.html 
[root@node1 html]# cat index.html 
node1

[root@node2 ~]# mkdir /var/www/html/ -p
[root@node2 ~]# cd /var/www/html/
[root@node2 html]# echo "node2" > index.html 
[root@node2 html]# cat index.html 
node2


[root@master ~]# kubectl apply -f test.yml 
pod/web created
[root@master ~]# kubectl get pod
NAME   READY   STATUS    RESTARTS   AGE
web    1/1     Running   0          8s
[root@master ~]# kubectl get pod -o wide
NAME   READY   STATUS    RESTARTS   AGE   IP            NODE    NOMINATED NODE   READINESS GATES
web    1/1     Running   0          45s   10.244.1.66   node1   <none>           <none>
[root@master ~]# curl 10.244.1.66
node1

总结：Pod中会有这几种类型的容器