(三)k8s集群pod存活性和就绪性探测

文章目录1 livenessProbe存活性探测1.1 exec探针1.2 httpGet探针2 readinessProbe就绪性探测1 livenessProbe存活性探测liveness存活性探测，可以通过我们自定义的命令或者一些内置的探测方法来探测pod中容器是否存活，如若探测到其状态或属性不符合我们定义的内容，那么就会使该容器重启来使之恢复正常。[root@master1 mani...

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2827人浏览 · 2019-01-24 11:02:11

RSQ博客 · 2019-01-24 11:02:11 发布

文章目录

1 livenessProbe存活性探测
- 1.1 exec探针
- 1.2 httpGet探针
2 readinessProbe就绪性探测

1 livenessProbe存活性探测

liveness存活性探测，可以通过我们自定义的命令或者一些内置的探测方法来探测pod中容器是否存活，如若探测到其状态或属性不符合我们定义的内容，那么就会使该容器重启来使之恢复正常。

[root@master1 manifests]# kubectl explain pods.spec.containers.livenessProbe
KIND:     Pod
VERSION:  v1

RESOURCE: livenessProbe <Object>

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-probes

     Probe describes a health check to be performed against a container to
     determine whether it is alive or ready to receive traffic.

FIELDS:
   exec	<Object>
     One and only one of the following should be specified. Exec specifies the
     action to take.

   failureThreshold	<integer>
     Minimum consecutive failures for the probe to be considered failed after
     having succeeded. Defaults to 3. Minimum value is 1.

   httpGet	<Object>
     HTTPGet specifies the http request to perform.

   initialDelaySeconds	<integer> 初始化探测，指定初始化时间
     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-probes

   periodSeconds	<integer>
     How often (in seconds) to perform the probe. Default to 10 seconds. Minimum
     value is 1.

   successThreshold	<integer>
     Minimum consecutive successes for the probe to be considered successful
     after having failed. Defaults to 1. Must be 1 for liveness. Minimum value
     is 1.

   tcpSocket	<Object>
     TCPSocket specifies an action involving a TCP port. TCP hooks not yet
     supported

   timeoutSeconds	<integer>
     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

1.1 exec探针

顾名思义，即可以指定命令，来定义我们要探测的命令

[root@master1 manifests]# cat liveness-exec.yaml 
apiVersion: v1
kind: Pod
metadata: 
  name: liveness-exec-pod
  namespace: default
spec:
  containers:
  - name: liveness-exec-container
    image: busybox:latest
    imagePullPolicy: IfNotPresent
    command: ["/bin/sh","-c","touch /tmp/healthy; sleep 30; rm -f /tmp/healthy; sleep 3600"]
    livenessProbe:
      exec:
        command: ["test","-e","/tmp/healthy"]
      initialDelaySeconds: 2
      periodSeconds: 3
[root@master1 manifests]# kubectl create -f liveness-exec.yaml
[root@master1 manifests]# kubectl get pods liveness-exec-pod
NAME                          READY   STATUS    RESTARTS   AGE
liveness-exec-pod             1/1     Running   0          7s
[root@master1 manifests]# kubectl get pods liveness-exec-pod
NAME                          READY   STATUS    RESTARTS   AGE
liveness-exec-pod             1/1     Running   0          17s
[root@master1 manifests]# kubectl get pods liveness-exec-pod
NAME                          READY   STATUS    RESTARTS   AGE
liveness-exec-pod             1/1     Running   1          70s
[root@master1 manifests]# kubectl get pods liveness-exec-pod
NAME                          READY   STATUS    RESTARTS   AGE
liveness-exec-pod             1/1     Running   2          2m38s

通过不停get pods，可以发现该pod会不断重启容器使之工作正常

1.2 httpGet探针

通过指定http端口及路径，来探测该服务是否处于正常状态

[root@master1 manifests]# cat liveness-httpget.yaml 
apiVersion: v1
kind: Pod
metadata: 
  name: liveness-httpget-pod
  namespace: default
spec:
  containers:
  - name: liveness-httpget-container
    image: nginx:1.14-alpine
    imagePullPolicy: IfNotPresent
    ports:
    - name: http
      containerPort: 80
    livenessProbe:
      httpGet:
        port: http
        path: /index.html
      initialDelaySeconds: 2
      periodSeconds: 3

periodSeconds：代表每次探测时间间隔
initialDelaySeconds：代表初始化延迟时间，即在一个容器启动后如果直接开始探测那么很有可能会直接探测失败，需要给一个系统初始化的时间

	[root@master1 manifests]# kubectl create -f liveness-httpget.yaml
	[root@master1 manifests]# kubectl get pods liveness-httpget-pod
	NAME                   READY   STATUS    RESTARTS   AGE
	liveness-httpget-pod   1/1     Running   0          8s
	
	# 手动删除index页面查看状态，会发现pod被重启，然后index页面又被创建
	[root@master1 manifests]# kubectl exec -it liveness-httpget-pod -- /bin/sh
	/ # rm -f /usr/share/nginx/html/index.html
	/ #
	[root@master1 manifests]# kubectl describe pods liveness-httpget-pod
	......
	    Last State:     Terminated
	      Reason:       Completed
	      Exit Code:    0
	      Started:      Fri, 21 Dec 2018 10:11:58 +0800
	      Finished:     Fri, 21 Dec 2018 10:14:12 +0800
	    Ready:          True
	    Restart Count:  1
	......
	[root@master1 manifests]# kubectl get pods liveness-httpget-pod
	NAME                   READY   STATUS    RESTARTS   AGE
	liveness-httpget-pod   1/1     Running   1          3m21s
	
	[root@master1 manifests]# kubectl exec -it liveness-httpget-pod -- /bin/sh
	/ # ls /usr/share/nginx/html/
	50x.html    index.html
	/ # exit

2 readinessProbe就绪性探测

当一个pod中的容器被创建后，正常工作情况下状态会转变至Running，在kubectl get pods的READY列的左侧数字会加1，代表该容器已然就绪，然实际上并不一定就绪，比如一个java服务，服务启动并运行起来可能需要一些时间，若在这个时间段内service把调度请求发给此pod的容器，这个容器又不能响应，就会存在问题，这个时候就要进行就绪性探测，来探测服务是否正常，正常之后kubectl get pods的READY状态左侧数字才会加1，此容器才会被service正常调度。

[root@master1 manifests]# kubectl explain pods.spec.containers.readinessProbe
KIND:     Pod
VERSION:  v1

RESOURCE: readinessProbe <Object>

DESCRIPTION:
     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

     Probe describes a health check to be performed against a container to
     determine whether it is alive or ready to receive traffic.

FIELDS:
   exec	<Object>
     One and only one of the following should be specified. Exec specifies the
     action to take.

   failureThreshold	<integer>
     Minimum consecutive failures for the probe to be considered failed after
     having succeeded. Defaults to 3. Minimum value is 1.

   httpGet	<Object>
     HTTPGet specifies the http request to perform.

   initialDelaySeconds	<integer>
     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-probes

   periodSeconds	<integer>
     How often (in seconds) to perform the probe. Default to 10 seconds. Minimum
     value is 1.

   successThreshold	<integer>
     Minimum consecutive successes for the probe to be considered successful
     after having failed. Defaults to 1. Must be 1 for liveness. Minimum value
     is 1.

   tcpSocket	<Object>
     TCPSocket specifies an action involving a TCP port. TCP hooks not yet
     supported

   timeoutSeconds	<integer>
     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

[root@master1 manifests]# vim rediness-httpget.yaml
apiVersion: v1
kind: Pod
metadata: 
  name: readiness-httpget-pod
  namespace: default
spec:
  containers:
  - name: readiness-httpget-container
    image: nginx:1.14-alpine
    imagePullPolicy: IfNotPresent
    ports:
    - name: http
      containerPort: 80
    readinessProbe:
      httpGet:
        port: http
        path: /index.html
      initialDelaySeconds: 1
      periodSeconds: 3
[root@master1 manifests]# kubectl create -f rediness-httpget.yaml 
pod/readiness-httpget-pod created

# 现在已然处于就绪状态
[root@master1 manifests]# kubectl get pods readiness-httpget-pod
NAME                    READY   STATUS    RESTARTS   AGE
readiness-httpget-pod   1/1     Running   0          35s

# 通过删除和创建index文件来观察pod就绪性状态
[root@master1 manifests]# kubectl exec -it readiness-httpget-pod -- /bin/sh
/ # rm -f /usr/share/nginx/html/index.html  删除index.html文件
/ # echo "hi" >> /usr/share/nginx/html/index.html   创建index.html文件

# 实时观察readiness-httpget-pod就绪性
[root@master1 manifests]# kubectl get pods readiness-httpget-pod -w
NAME                    READY   STATUS    RESTARTS   AGE
readiness-httpget-pod   0/1     Running   0          117s
readiness-httpget-pod   1/1   Running   0     2m27s

在进行存活性和就绪性探测的时候，每次只需要定义其中一个探针即可

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