一、容器探测器
1、所谓的容器探测无非就是我们在里面设置了一些探针，或者称之为传感器来获取相应的数据作为判定其存活与否或就绪与否的标准，目前k8s所支持的存活性和就绪性探测方式都是一样的。
2、k8s的探针类型有三种
1、ExecAction
2、TCPSocketAction：TCPSocket探针
3、HTTPGetAction ： 如果对方是http服务那么直接向对方发http的get请求就可以了
3、相应字段在 pods.spec.containers 之上
a、livenessProbe
[root@k8smaster ~]# kubectl explain pods.spec.containers.livenessProbe
KIND: Pod
VERSION: v1
RESOURCE: livenessProbe
b、readinessProbe
c、lifecycle
4、exec指针探测
[root@k8smaster ~]# kubectl explain pods.spec.containers.livenessProbe.exec
KIND: Pod
VERSION: v1
RESOURCE: exec
[root@k8smaster manifests]# ls
liveness-exec.yaml pod-demo.yaml
[root@k8smaster 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"] #判断此文件是否存在 initialDelaySeconds: 1 #容器启动后等待1秒开始探测 periodSeconds: 3 #每隔3秒探测一次 restartPolicy: Always [root@k8smaster manifests]# kubectl get pods NAME READY STATUS RESTARTS AGE liveness-exec-pod 1/1 Running 6 9m myapp-848b5b879b-5k4s4 1/1 Running 0 4d myapp-848b5b879b-bzblz 1/1 Running 0 4d myapp-848b5b879b-hzbf5 1/1 Running 0 4d nginx-deploy-5b595999-d9lv5 1/1 Running 0 4d pod-demo 2/2 Running 3 5h [root@k8smaster manifests]# kubectl describe pod liveness-exec-pod Name: liveness-exec-pod Namespace: default Priority: 0 PriorityClassName: Node: k8snode2/192.168.10.12 Start Time: Thu, 09 May 2019 19:59:15 +0800 Labels: Annotations: Status: Running IP: 10.244.2.17 Containers: liveness-exec-container: Container ID: docker://37b9faa3b66df5f74ce43943e20d414a6e0498b261b65e11e7c89ab26c633109 Image: busybox:latest Image ID: docker-pullable://busybox@sha256:4b6ad3a68d34da29bf7c8ccb5d355ba8b4babcad1f99798204e7abb43e54ee3d Port: Host Port: Command: /bin/sh -c touch /tmp/healthy; sleep 30; rm -f /tmp/healthy; sleep 3600 State: Running Started: Thu, 09 May 2019 20:07:42 +0800 Last State: Terminated Reason: Error Exit Code: 137 Started: Thu, 09 May 2019 20:05:00 +0800 Finished: Thu, 09 May 2019 20:06:09 +0800 Ready: True Restart Count: 6 Liveness: exec [test -e /tmp/healthy] delay=1s timeout=1s period=3s #success=1 #failure=3 Environment: Mounts: /var/run/secrets/kubernetes.io/serviceaccount from default-token-jvtl7 (ro) Conditions: Type Status Initialized True Ready True ContainersReady True PodScheduled True Volumes: default-token-jvtl7: Type: Secret (a volume populated by a Secret) SecretName: default-token-jvtl7 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 Pulled 4d (x4 over 4d) kubelet, k8snode2 Container image "busybox:latest" already present on machine Normal Created 4d (x4 over 4d) kubelet, k8snode2 Created container Normal Started 4d (x4 over 4d) kubelet, k8snode2 Started container Normal Killing 4d (x3 over 4d) kubelet, k8snode2 Killing container with id docker://liveness-exec-container:Container failed liveness probe.. Container will be killed and recreate d. Warning Unhealthy 4d (x13 over 4d) kubelet, k8snode2 Liveness probe failed: Normal Scheduled 9m default-scheduler Successfully assigned default/liveness-exec-pod to k8snode2
5、基于tcpSocket探测
[root@k8smaster manifests]# kubectl explain pods.spec.containers.livenessProbe.tcpSocket
KIND: Pod
VERSION: v1
RESOURCE: tcpSocket
6、httpGet探测
[root@k8smaster manifests]# kubectl explain pods.spec.containers.livenessProbe.httpGet
KIND: Pod
VERSION: v1
RESOURCE: httpGet
案例如下
[root@k8smaster manifests]# cat 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 #也可以使用80 path: /index.html initialDelaySeconds: 1 #容器启动后等待1秒开始探测 periodSeconds: 3 #每隔3秒探测一次 restartPolicy: Always
7、就绪性探测，其与service调度有着重要的关联性。如果不做就绪性探测那么pod刚创建就立即被关联到service后端对象中，此时pod如果未就绪将造成服务无法被访问，因此几乎只要使用pod就必须做readinessProbe（就绪性检测）。
其检测方式和探针与liveness一样，只是目标不一样，livenessProbe只是为了判断存活与否，而readinessProbe则是用来判断它就绪与否。因此只是探测命令可能会不一样。
[root@k8smaster manifests]# cat readiness-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 #也可以使用80 path: /index.html initialDelaySeconds: 1 #容器启动后等待1秒开始探测 periodSeconds: 3 #每隔3秒探测一次 restartPolicy: Always [root@k8smaster manifests]# kubectl create -f readiness-httpget.yaml pod/readiness-httpget-pod created [root@k8smaster manifests]# kubectl get pods NAME READY STATUS RESTARTS AGE liveness-httpget-pod 1/1 Running 1 32m myapp-848b5b879b-5k4s4 1/1 Running 0 4d myapp-848b5b879b-bzblz 1/1 Running 0 4d myapp-848b5b879b-hzbf5 1/1 Running 0 4d nginx-deploy-5b595999-d9lv5 1/1 Running 0 5d pod-demo 2/2 Running 4 6h readiness-httpget-pod 1/1 Running 0 6s [root@k8smaster manifests]# kubectl describe pod readiness-httpget-pod Name: readiness-httpget-pod Namespace: default Priority: 0 PriorityClassName:Node: k8snode2/192.168.10.12 Start Time: Thu, 09 May 2019 21:02:50 +0800 Labels: Annotations: Status: Running IP: 10.244.2.19 Containers: readiness-httpget-container: Container ID: docker://2972a892e1c91c2cfa6168f5729cbf1dae02e079f5bd1e8dc370e2ed56dcbf61 Image: ikubernetes/myapp:v1 Image ID: docker-pullable://ikubernetes/myapp@sha256:9c3dc30b5219788b2b8a4b065f548b922a34479577befb54b03330999d30d513 Port: 80/TCP Host Port: 0/TCP State: Running Started: Thu, 09 May 2019 21:02:51 +0800 Ready: True Restart Count: 0 Readiness: http-get http://:http/index.html delay=1s timeout=1s period=3s #success=1 #failure=3 Environment: Mounts: /var/run/secrets/kubernetes.io/serviceaccount from default-token-jvtl7 (ro) Conditions: Type Status Initialized True Ready True ContainersReady True PodScheduled True Volumes: default-token-jvtl7: Type: Secret (a volume populated by a Secret) SecretName: default-token-jvtl7 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 Pulled 4d kubelet, k8snode2 Container image "ikubernetes/myapp:v1" already present on machine Normal Created 4d kubelet, k8snode2 Created container Normal Started 4d kubelet, k8snode2 Started container Normal Scheduled 23s default-scheduler Successfully assigned default/readiness-httpget-pod to k8snode2 #进入容器删除index.html发现不再ready [root@k8smaster manifests]# kubectl get pods NAME READY STATUS RESTARTS AGE liveness-httpget-pod 1/1 Running 1 34m myapp-848b5b879b-5k4s4 1/1 Running 0 4d myapp-848b5b879b-bzblz 1/1 Running 0 4d myapp-848b5b879b-hzbf5 1/1 Running 0 4d nginx-deploy-5b595999-d9lv5 1/1 Running 0 5d pod-demo 2/2 Running 4 6h readiness-httpget-pod 0/1 Running 0 2m
8、lifecycle
[root@k8smaster manifests]# kubectl explain pods.spec.containers.lifecycle
KIND: Pod
VERSION: v1
RESOURCE: lifecycle
a、postStart ，默认会在容器的command命令运行完后再运行其定义的命令。
[root@k8smaster manifests]# more poststart-pod.yaml apiVersion: v1 kind: Pod metadata: name: poststart-pod namespace: default spec: containers: - name: busybox-pod image: busybox:latest imagePullPolicy: IfNotPresent lifecycle: postStart: exec: command: ["mkdir","-p","/data/web/html"] command: ["/bin/sh","-c"] #默认此命令+args执行完才会执行上面的postStart.exec.command中的命令 args: ["sleep 3600"] [root@k8smaster manifests]# kubectl exec -it poststart-pod /bin/sh / # ls /data/web/html/ / # exit [root@k8smaster manifests]# kubectl get pods NAME READY STATUS RESTARTS AGE liveness-httpget-pod 1/1 Running 1 1h myapp-848b5b879b-5k4s4 1/1 Running 0 4d myapp-848b5b879b-bzblz 1/1 Running 0 4d myapp-848b5b879b-hzbf5 1/1 Running 0 4d nginx-deploy-5b595999-d9lv5 1/1 Running 0 5d pod-demo 2/2 Running 5 7h poststart-pod 1/1 Running 0 1m readiness-httpget-pod 1/1 Running 0 58m
b、preStop ，和postStart类似