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k8s学习|K8S学习之容器探测 livenessProbe、readinessProbe、startupProbe、lifecycle

容器运维Kubernetesk8s学习

容器探测 所谓容器探测就是我们在里面设置了一些探针，或者传感器来获取相应的数据用来判断容器是否启动、存活、就绪的标准；
目前k8s支持的探针有三种：livenessProbe、readinessProbe、startupProbe。（可以混用）
探测类型有三种：exec、httpGet、tcpSocket。我们平时定义的时候只需要定义任意一个即可。如果探测失败，kubelet杀掉该容器，并根据容器的重启策略做相应的处理（readinessProbe不会重启pod）。
命令行查看探针

[root@master ~]# kubectl explain pods.spec.containers ... livenessProbe Periodic probe of container liveness. Container will be restarted if the probe fails. Cannot be updated. More info: https://kubernetes.io/docs/concepts/workloads/pods/pod-lifecycle#container-probes readinessProbe Periodic probe of container service readiness. Container will be removed from service endpoints if the probe fails. Cannot be updated. More info: https://kubernetes.io/docs/concepts/workloads/pods/pod-lifecycle#container-probes startupProbe StartupProbe indicates that the Pod has successfully initialized. If specified, no other probes are executed until this completes successfully. If this probe fails, the Pod will be restarted, just as if the livenessProbe failed. This can be used to provide different probe parameters at the beginning of a Pod's lifecycle, when it might take a long time to load data or warm a cache, than during steady-state operation. This cannot be updated. This is a beta feature enabled by the StartupProbe feature flag. More info: https://kubernetes.io/docs/concepts/workloads/pods/pod-lifecycle#container-probes
查看livenessprobe
[root@master ~]# kubectl explain pods.spec.containers.livenessProbe KIND:Pod VERSION:v1RESOURCE: livenessProbe DESCRIPTION: Periodic probe of container liveness. Container will be restarted if the probe fails. Cannot be updated. More info: https://kubernetes.io/docs/concepts/workloads/pods/pod-lifecycle#container-probesProbe describes a health check to be performed against a container to determine whether it is alive or ready to receive traffic.FIELDS: exec One and only one of the following should be specified. Exec specifies the action to take.failureThreshold Minimum consecutive failures for the probe to be considered failed after having succeeded. Defaults to 3. Minimum value is 1.httpGet HTTPGet specifies the http request to perform.initialDelaySeconds Number of seconds after the container has started before liveness probes are initiated. More info: https://kubernetes.io/docs/concepts/workloads/pods/pod-lifecycle#container-probesperiodSeconds How often (in seconds) to perform the probe. Default to 10 seconds. Minimum value is 1.successThreshold Minimum consecutive successes for the probe to be considered successful after having failed. Defaults to 1. Must be 1 for liveness and startup. Minimum value is 1.tcpSocket TCPSocket specifies an action involving a TCP port. TCP hooks not yet supportedtimeoutSeconds Number of seconds after which the probe times out. Defaults to 1 second. Minimum value is 1. More info: https://kubernetes.io/docs/concepts/workloads/pods/pod-lifecycle#container-probes
参数简介
failureThreshold失败判断，默认失败3次 initialDelaySeconds 初始化延迟等待时间 periodSeconds周期间隔时长，默认10s successThreshold启动几秒后，认为成功，默认1s timeoutSeconds探测后的响应时间，默认1s

ReadinessProbe、startupprobe各项参数解释同上面的livenessProbe
查看livenessProbe下的exec用法
[root@master ~]# kubectl explain pods.spec.containers.livenessProbe.exec KIND:Pod VERSION:v1RESOURCE: exec DESCRIPTION: One and only one of the following should be specified. Exec specifies the action to take.ExecAction describes a "run in container" action.FIELDS: command<[]string> Command is the command line to execute inside the container, the working directory for the command is root ('/') in the container's filesystem. The command is simply exec'd, it is not run inside a shell, so traditional shell instructions ('|', etc) won't work. To use a shell, you need to explicitly call out to that shell. Exit status of 0 is treated as live/healthy and non-zero is unhealthy.
[root@master ~]# vim liveness-exec.yaml
apiVersion: v1 kind: Pod metadata: name: liveness-exec-container namespace: default spec: containers: - name: liveness-exec-container image: busybox:latest imagePullPolicy: IfNotPresent command: ["/bin/sh","-c","touch /tmp/healthy; sleep 30; rm -rf /tmp/healthy; sleep 3600"] livenessProbe: exec: command: ["test","-e","/tmp/healthy"]#检测文件是否存在，判断存活 initialDelaySeconds: 1 periodSeconds: 3[root@master ~]# kubectl get pod NAMEREADYSTATUSRESTARTSAGE liveness-exec-container1/1Running07s [root@master ~]# kubectl describe pod liveness-exec-container ... Events: TypeReasonAgeFromMessage ------------------------- NormalScheduled16sdefault-schedulerSuccessfully assigned default/liveness-exec-container to node1 NormalPulled16skubeletContainer image "busybox:latest" already present on machine NormalCreated16skubeletCreated container liveness-exec-container NormalStarted15skubeletStarted container liveness-exec-container 此时可以看到容器启动成功，等待一段时间再次查看，会发现Liveness probe failed，容器重启 [root@master ~]# kubectl describe pod liveness-exec-container ... Restart Count:3 ... Events: TypeReasonAgeFromMessage ------------------------- NormalScheduled40sdefault-schedulerSuccessfully assigned default/liveness-exec-container to node1 NormalPulled40skubeletContainer image "busybox:latest" already present on machine NormalCreated40skubeletCreated container liveness-exec-container NormalStarted39skubeletStarted container liveness-exec-container WarningUnhealthy2s (x3 over 8s)kubeletLiveness probe failed: NormalKilling2skubeletContainer liveness-exec-container failed liveness probe, will be restarted

查看livenessProbe下的httpGet的使用
[root@master ~]# kubectl explain pods.spec.containers.livenessProbe.httpGet KIND:Pod VERSION:v1RESOURCE: httpGet DESCRIPTION: HTTPGet specifies the http request to perform.HTTPGetAction describes an action based on HTTP Get requests.FIELDS: host > Host name to connect to, defaults to the pod IP. You probably want to set "Host" in httpHeaders instead.httpHeaders<[]Object> Custom headers to set in the request. HTTP allows repeated headers.path > Path to access on the HTTP server.port > -required- Name or number of the port to access on the container. Number must be in the range 1 to 65535. Name must be an IANA_SVC_NAME.scheme> Scheme to use for connecting to the host. Defaults to HTTP.
[root@master ~]# vim liveness-httpget.yaml
apiVersion: v1 kind: Pod metadata: name: liveness-httpget-pod namespace: default spec: containers: - name: liveness-httpget-container image: ikubernetes/myapp:v1 imagePullPolicy: IfNotPresent ports: - name: http containerPort: 80 livenessProbe: httpGet: port: http path: /index.html initialDelaySeconds: 1 periodSeconds: 3

查看pod的信息，此时pod 能够访问
[root@master ceshi]# kubectl get pod NAMEREADYSTATUSRESTARTSAGE liveness-httpget-pod1/1Running018s [root@master ceshi]# kubectl get pod -owide NAMEREADYSTATUSRESTARTSAGEIPNODENOMINATED NODEREADINESS GATES liveness-httpget-pod1/1Running023s10.244.1.34node1 [root@master ceshi]# curl 10.244.1.34 Hello MyApp [root@master ~]#kubectl describe pod liveness-httpget-pod ... Events: TypeReasonAgeFromMessage ------------------------- NormalScheduled1m30sdefault-schedulerSuccessfully assigned default/liveness-httpget-pod to node1 NormalPulled1m30skubeletContainer image "ikubernetes/myapp:v1" already present on machine NormalCreated1m30skubeletCreated container liveness-httpget-container NormalStarted1m30skubeletStarted container liveness-httpget-container

进入容器删除livenessProbe的探测的文件index.html。退出稍等一下，观察会发现pod，依然能访问
[root@master ~]# kubectl exec -it liveness-httpget-pod -- /bin/sh / # rm -rf /usr/share/nginx/html/index.html / # exit [root@master ~]#curl 10.244.1.34 Hello MyApp [root@master ~]# kubectl get pod -owide NAMEREADYSTATUSRESTARTSAGEIPNODENOMINATED NODEREADINESS GATES liveness-httpget-pod1/1Running16m25s10.244.1.34node1[root@master ~]#kubectl describe pod liveness-httpget-pod ... Restart Count:1 Events: TypeReasonAgeFromMessage ------------------------- NormalScheduled5m11sdefault-schedulerSuccessfully assigned default/liveness-httpget-pod to node1 NormalPulled6s (x2 over 5m10s)kubeletContainer image "ikubernetes/myapp:v1" already present on machine NormalCreated6s (x2 over 5m10s)kubeletCreated container liveness-httpget-container NormalStarted6s (x2 over 5m10s)kubeletStarted container liveness-httpget-container WarningUnhealthy6s (x3 over 12s)kubeletLiveness probe failed: HTTP probe failed with statuscode: 404 NormalKilling6skubeletContainer liveness-httpget-container failed liveness probe, will be restarted

readnessProbe（容器就绪性探测）使用
[root@master ~]# vim readliness-httpget.yaml
apiVersion: v1 kind: Pod metadata: name: readiness-httpget-pod namespace: default spec: containers: - name: readiness-httpget-container image: ikubernetes/myapp:v1 imagePullPolicy: IfNotPresent ports: - name: http containerPort: 80 readinessProbe: httpGet: port: http path: /index.html initialDelaySeconds: 1 periodSeconds: 3

此时查看pod
[root@master ~]# kubectl apply -f readliness-httpget.yaml pod/readiness-httpget-pod created [root@master ~]# kubectl get pod -owide NAMEREADYSTATUSRESTARTSAGEIPNODENOMINATED NODEREADINESS GATES readiness-httpget-pod1/1Running026s10.244.1.35node1 [root@master ~]# curl 10.244.1.35 Hello MyApp

容器就绪性状态检测index.html是否存在，如果把index.html删除，那么容器处于不正常运行，**但不会重启。**此时
kubectl get pod的READY状态是0/1
kubectl descript pod 显示404报错访问的网页是默认的，不是Hello MyApp。
kubectl logs readiness-httpget-pod 显示没有这个文件
[root@master ~]# kubectl exec -it readiness-httpget-pod -- /bin/sh / # rm -rf /usr/share/nginx/html/index.html / # exit [root@master ~]# kubectl get pod NAMEREADYSTATUSRESTARTSAGE readiness-httpget-pod0/1Running05m3s [root@master ~]# kubectl describe pod readiness-httpget-pod ... Events: ... WarningUnhealthy3m1s (x53 over 5m37s)kubeletReadiness probe failed: HTTP probe failed with statuscode: 404 [root@master ~]# kubectl logs readiness-httpget-pod open() "/usr/share/nginx/html/index.html" failed (2: No such file or directory),

进入容器再次创建index.html时，会发现容器就绪，可以正常访问
[root@master ~]# kubectl exec -it readiness-httpget-pod -- /bin/sh / # echo "Hello MyApp" >> /usr/share/nginx/html/index.html / # exit [root@master ~]# kubectl get pod NAMEREADYSTATUSRESTARTSAGE readiness-httpget-pod1/1Running010m [root@master ~]# curl 10.244.1.35 Hello MyApp

3.lifecycle生命周期讲解
[root@master ~]# kubectl explain pods.spec.containers.lifecycle
PostStart ：容器创建成功后，运行前的任务，用于资源部署、环境准备等。如果操作失败，容器根据重启策略决定是否重启，
PreStop ：在容器被终止前的任务，用于优雅关闭应用程序、通知其他系统等等。
[root@master ~]# kubectl explain pods.spec.containers.lifecycle.postStart
同样也是exec、httpGet、tcpSocket三种方式
postStart例子 初始化操作使用的比较多，实际生产使用频次较少
这里前钩子修改了index.html文件，访问时是新的界面home
[root@master ~]# vim poststart-nginx.yaml
apiVersion: v1 kind: Pod metadata: name: poststart-nginx namespace: default spec: containers: - name: poststart-nginx image: nginx imagePullPolicy: IfNotPresent lifecycle: postStart: exec: command: ["/bin/sh","-c","echo home >> /usr/share/nginx/html/index.html"] ports: - name: http containerPort: 80 [root@master ~]# kubectl get pod -owide NAMEREADYSTATUSRESTARTSAGEIPNODENOMINATED NODEREADINESS GATES poststart-nginx1/1Running05s10.244.1.36node1 [root@master ~]# curl 10.244.1.36 home

prestop举例：
PreStop在整个生命周期中比较有用，实用场景也比较多。 比如：
1.关闭前等待某一个状态完成；
2.关闭前同步一些状态（数据）到其他的地方；
3.关闭前通知某一个系统或者更新一个状态；
[root@master ~]# vim preStop-nginx.yaml 这里实现了nginx的优雅退出
apiVersion: v1 kind: Pod metadata: name: prestop-nginx namespace: default spec: containers: - name: prestop-nginx image: nginx imagePullPolicy: IfNotPresent lifecycle: preStop: exec: command: ["/usr/local/nginx/sbin/nginx","-s","quit"] ports: - name: http containerPort: 80

【k8s学习|K8S学习之容器探测 livenessProbe、readinessProbe、startupProbe、lifecycle】混合配置，这里有个参考的，可以看看
https://www.cnblogs.com/superlinux/p/14933961.html

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