Kubernetes 1.19.0——健康性检查

原创

gz_naldo

修改于 2020-10-09 10:19:59

4282

修改于 2020-10-09 10:19:59

文章被收录于专栏：CloudComputingCloudComputing

探测的目的

deployment的作用是用来维持 pod的健壮性

当pod挂掉之后，deployment会生成新的pod

但如果pod是正常运行的，而pod里面又出了问题，此时deployment是监测不到的。

故此需要探测（probe）

用户定义 “出现什么样的状况 “才叫出问题

当probe监测到此问题，会认为pod出现了问题，执行“重启大法”来解决问题

参数的意义

initialDelaySeconds：容器启动后第一次执行探测是需要等待多少秒。

periodSeconds：执行探测的频率，默认是10秒，最小1秒。

timeoutSeconds：探测超时时间，默认1秒，最小1秒。

successThreshold：探测失败后，最少连续探测成功多少次才被认定为成功，默认是1，对于liveness必须是1，最小值是1。

failureThreshold：当 Pod 启动了并且探测到失败，Kubernetes 的重试次数。存活探测情况下的放弃就意味着重新启动容器。就绪探测情况下的放弃 Pod 会被打上未就绪的标签。默认值是 3。最小值是 1

https://kubernetes.io/zh/docs/tasks/configure-pod-container/configure-liveness-readiness-

startup-probes/#configure-probes

liveness probe --command

[root@vms61 chap7-probe]# cat pod1.yaml 
apiVersion: v1 
kind: Pod 
metadata: 
  labels: 
    test: liveness 
  name: pod1 
spec: 
  terminationGracePeriodSeconds: 0
  containers: 
  - name: liveness 
    image: busybox
    imagePullPolicy: IfNotPresent
    args: 
    - /bin/sh 
    - -c 
    - touch /tmp/healthy; sleep 30; rm -rf /tmp/healthy; sleep 100000 
    livenessProbe: 
      exec: 
        command:
        - cat
        - /tmp/healthy
      initialDelaySeconds: 5            
      periodSeconds: 5   
[root@vms61 chap7-probe]# kubectl apply -f pod1.yaml 
pod/pod1 created

通过watch -n .5 'kubectl get pods;kubectl exec pod1 -- ls /tmp/ 每隔0.5秒检测一次

liveness probe --httpGET

[root@vms61 chap7-probe]# cat pod2.yaml 
apiVersion: v1
kind: Pod
metadata: 
  labels: 
    test: liveness
  name: pod1
spec: 
  containers: 
  - name: liveness
    image: nginx
    imagePullPolicy: IfNotPresent
    livenessProbe: 
      failureThreshold: 3
      httpGet: 
        path: /index.html
        port: 80
        scheme: HTTP
      initialDelaySeconds: 10
      periodSeconds: 10
      successThreshold: 1
      timeoutSeconds: 10
[root@vms61 chap7-probe]# kubectl apply -f pod2.yaml 
pod/pod1 created
[root@vms61 chap7-probe]# kubectl exec pod1 -- rm /usr/share/nginx/html/index.html

liveness probe --tcp

[root@vms61 chap7-probe]# cat pod3.yaml 
apiVersion: v1
kind: Pod
metadata: 
  labels: 
    test: liveness
  name: pod1
spec: 
  containers: 
  - name: liveness
    image: nginx
    imagePullPolicy: IfNotPresent
    livenessProbe: 
      failureThreshold: 3
      tcpSocket:
        port: 80
        scheme: HTTP
      initialDelaySeconds: 10
      periodSeconds: 10
      successThreshold: 1
      timeoutSeconds: 10

readiness probe --command

liveness通过重启来解决问题

readiness检测到问题，并不重启

[root@vms61 chap7-probe]# cat web1.yaml 
apiVersion: apps/v1
kind: Deployment
metadata:
  creationTimestamp: null
  labels:
    app: web1
  name: web1
spec:
  replicas: 3
  selector:
    matchLabels:
      app: web1
  strategy: {}
  template:
    metadata:
      creationTimestamp: null
      labels:
        app: web1
    spec:
      containers:
      - image: nginx
        imagePullPolicy: IfNotPresent
        name: nginx
        resources: {}
        readinessProbe:
          exec:
            command:
            - cat
            - /usr/share/nginx/html/index.html
          initialDelaySeconds: 5
          periodSeconds: 5
status: {}
[root@vms61 chap7-probe]# kubectl apply -f web1.yaml 
deployment.apps/web1 created
[root@vms61 chap7-probe]# kubectl get pods
NAME                    READY   STATUS    RESTARTS   AGE
web1-58468bf858-4r89d   0/1     Running   0          6s
web1-58468bf858-hzs2b   0/1     Running   0          6s
web1-58468bf858-kr8l9   0/1     Running   0          6s
[root@vms61 chap7-probe]# kubectl exec -it web1-58468bf858-4r89d -- bash 
root@web1-58468bf858-4r89d:/# echo 11111 > /usr/share/nginx/html/index.html 
root@web1-58468bf858-4r89d:/# exit
exit
[root@vms61 chap7-probe]# kubectl exec -it web1-58468bf858-hzs2b -- bash 
root@web1-58468bf858-hzs2b:/# echo 22222 > /usr/share/nginx/html/index.html 
root@web1-58468bf858-hzs2b:/# exit
exit
[root@vms61 chap7-probe]# kubectl exec -it web1-58468bf858-kr8l9 -- bash 
root@web1-58468bf858-kr8l9:/# echo 33333 > /usr/share/nginx/html/index.html 
root@web1-58468bf858-kr8l9:/# exit
exit

[root@vms61 chap7-probe]# kubectl expose deployment web1 --port=80 --target-port=80
service/web1 exposed
[root@vms61 chap7-probe]# kubectl get svc
NAME   TYPE        CLUSTER-IP       EXTERNAL-IP   PORT(S)   AGE
web1   ClusterIP   10.111.157.194   <none>        80/TCP    4s
[root@vms61 chap7-probe]# curl -s 10.111.157.194
22222
[root@vms61 chap7-probe]# curl -s 10.111.157.194
33333
[root@vms61 chap7-probe]# curl -s 10.111.157.194
11111
[root@vms61 chap7-probe]# curl -s 10.111.157.194
33333
[root@vms61 chap7-probe]# curl -s 10.111.157.194
22222
[root@vms61 chap7-probe]# curl -s 10.111.157.194
11111