容器探针
探针是由 kubelet对容器执行的定期诊断。要执行诊断， kubelet 调用由容器实现的 Handler 。有三种类型的处理程序：
- ExecAction ：在容器内执行指定命令。如果命令退出时返回码为 0 则认为诊断成功。
- TCPSocketAction ：对指定端口上的容器的 IP 地址进行 TCP 检查。如果端口打开，则诊断被认为是成功的。
- HTTPGetAction ：对指定的端口和路径上的容器的 IP 地址执行 HTTP Get 请求。如果响应的状态码大于等于 200 且小于 400 ，则诊断被认为是成功的
每次探测都将获得以下三种结果之一：
- 成功：容器通过了诊断。
- 失败：容器未通过诊断。
- 未知：诊断失败，因此不会采取任何行动
探针的方式
- livenessProbe ：指示容器是否正在运行。如果存活探测失败，则 kubelet 会杀死容器，并且容器将受到其 重启策略 的影响。如果容器不提供存活探针，则默认状态为 Success
- readinessProbe ：指示容器是否准备好服务请求。如果就绪探测失败，端点控制器将从与 Pod 匹配的所有 Service 的端点中删除该 Pod 的 IP 地址。初始延迟之前的就绪状态默认为 Failure 。如果容器不提供就绪探针，则默认状态为 Success。
测试
检测探针 - 就绪检测
read.yaml
[root@k8s-master mnt]# cat read.yaml
apiVersion: v1
kind: Pod
metadata:
name: readiness-httpget-pod
namespace: default
spec:
containers:
- name: readiness-httpget-container
image: wangyanglinux/myapp:v1
imagePullPolicy: IfNotPresent
readinessProbe:
httpGet:
port: 80
path: /index1.html
initialDelaySeconds: 1
periodSeconds: 3
[root@k8s-master mnt]#
[root@k8s-master mnt]# vim read.yaml
[root@k8s-master mnt]# kubectl create -f read.yaml
pod/readiness-httpget-pod created
[root@k8s-master mnt]# kubectl get pod
NAME READY STATUS RESTARTS AGE
myapp-pod 1/1 Running 0 70m
readiness-httpget-pod 0/1 Running 0 17s
[root@k8s-master mnt]# kubectl describe pod readiness-httpget-pod
Name: readiness-httpget-pod
Namespace: default
Priority: 0
Node: k8s-node01/192.168.180.133
Start Time: Wed, 18 Dec 2019 23:12:59 +0800
Labels:
Annotations:
Status: Running
IP: 10.244.2.10
IPs:
IP: 10.244.2.10
Containers:
readiness-httpget-container:
Container ID: docker://566ff6cdcf44daaba316b796fb8bf6f9563ddd44000c9ae9f572fd0a6719684c
Image: wangyanglinux/myapp:v1
Image ID: docker-pullable://wangyanglinux/myapp@sha256:9c3dc30b5219788b2b8a4b065f548b922a34479577befb54b03330999d30d513
Port:
Host Port:
State: Running
Started: Wed, 18 Dec 2019 23:13:01 +0800
Ready: False
Restart Count: 0
Readiness: http-get http://:80/index1.html delay=1s timeout=1s period=3s #success=1 #failure=3
Environment:
Mounts:
/var/run/secrets/kubernetes.io/serviceaccount from default-token-gx2h8 (ro)
Conditions:
Type Status
Initialized True
Ready False
ContainersReady False
PodScheduled True
Volumes:
default-token-gx2h8:
Type: Secret (a volume populated by a Secret)
SecretName: default-token-gx2h8
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 Scheduled default-scheduler Successfully assigned default/readiness-httpget-pod to k8s-node01
Normal Pulled 66s kubelet, k8s-node01 Container image "wangyanglinux/myapp:v1" already present on machine
Normal Created 66s kubelet, k8s-node01 Created container readiness-httpget-container
Normal Started 66s kubelet, k8s-node01 Started container readiness-httpget-container
Warning Unhealthy 0s (x22 over 63s) kubelet, k8s-node01 Readiness probe failed: HTTP probe failed with statuscode: 404
[root@k8s-master mnt]# kubectl exec readiness-httpget-pod -it /bin/sh
/ # ls
bin dev etc home lib media mnt proc root run sbin srv sys tmp usr var
/ # cd /usr/share/nginx
/usr/share/nginx # ls -l
total 0
drwxr-xr-x 1 root root 24 Feb 25 2018 html
/usr/share/nginx # cd html/
/usr/share/nginx/html # ls -l
total 8
-rw-r--r-- 1 root root 537 Jan 10 2018 50x.html
-rw-r--r-- 1 root root 65 Mar 2 2018 index.html
/usr/share/nginx/html # cat index.html
Hello MyApp | Version: v1 | Pod Name
/usr/share/nginx/html # echo "123" >> index1.html
/usr/share/nginx/html # exit
[root@k8s-master mnt]# kubectl get pod
NAME READY STATUS RESTARTS AGE
myapp-pod 1/1 Running 1 73m
readiness-httpget-pod 1/1 Running 0 3m41s 说明：由于index1.html不存在，会导致他重启，手动创建后就正常了。
检测探针 - 存活检测
[root@k8s-master mnt]# cat live-exec.yaml
apiVersion: v1
kind: Pod
metadata:
name: liveness-exec-pod
namespace: default
spec:
containers:
- name: liveness-exec-container
image: busybox
imagePullPolicy: IfNotPresent
command: ["/bin/sh","-c","touch /tmp/live ; sleep 60; rm -rf /tmp/live; sleep 3600"]
livenessProbe:
exec:
command: ["test","-e","/tmp/live"]
initialDelaySeconds: 1
periodSeconds: 3
[root@k8s-master mnt]#[root@k8s-master mnt]# vim live-exec.yaml
[root@k8s-master mnt]# kubectl create -f live-exec.yaml
pod/liveness-exec-pod created
[root@k8s-master mnt]# kubectl get pod -w
NAME READY STATUS RESTARTS AGE
liveness-exec-pod 1/1 Running 0 25s
myapp-pod 1/1 Running 1 81m
readiness-httpget-pod 1/1 Running 0 11m
liveness-exec-pod 1/1 Running 1 101s
liveness-exec-pod 1/1 Running 2 3m19s
^Z
[1]+ 已停止 kubectl get pod -w说明：由于/tmp/live不存在，会一直重启
[root@k8s-master mnt]# cat live-http.yaml
apiVersion: v1
kind: Pod
metadata:
name: liveness-httpget-pod
namespace: default
spec:
containers:
- name: liveness-httpget-container
image: wangyanglinux/myapp:v1
imagePullPolicy: IfNotPresent
ports:
- name: http
containerPort: 80
livenessProbe:
httpGet:
port: http
path: /index.html
initialDelaySeconds: 1
periodSeconds: 3
timeoutSeconds: 10
[root@k8s-master mnt]#
[root@k8s-master mnt]# kubectl create -f live-http.yaml
pod/liveness-httpget-pod created
[root@k8s-master mnt]# kubectl get pod
NAME READY STATUS RESTARTS AGE
liveness-httpget-pod 1/1 Running 0 14s
myapp-pod 1/1 Running 1 90m
readiness-httpget-pod 1/1 Running 0 20m
[root@k8s-master mnt]# kubectl get pod -o wide
NAME READY STATUS RESTARTS AGE IP NODE NOMINATED NODE READINESS GATES
liveness-httpget-pod 1/1 Running 0 26s 10.244.2.12 k8s-node01
myapp-pod 1/1 Running 1 90m 10.244.1.9 k8s-node02
readiness-httpget-pod 1/1 Running 0 20m 10.244.2.10 k8s-node01
[root@k8s-master mnt]# curl 10.244.2.12
Hello MyApp | Version: v1 | Pod Name
[root@k8s-master mnt]# curl 10.244.2.12/index.html
Hello MyApp | Version: v1 | Pod Name
[root@k8s-master mnt]# kubectl exec liveness-httpget-pod -it -- /bin/sh
/ # cd /usr/share/nginx/html/
/usr/share/nginx/html # ls -l
total 8
-rw-r--r-- 1 root root 537 Jan 10 2018 50x.html
-rw-r--r-- 1 root root 65 Mar 2 2018 index.html
/usr/share/nginx/html # rm -rf index.html
/usr/share/nginx/html # exit
[root@k8s-master mnt]# kubectl get pod
NAME READY STATUS RESTARTS AGE
liveness-httpget-pod 1/1 Running 0 2m24s
myapp-pod 1/1 Running 1 92m
readiness-httpget-pod 1/1 Running 0 22m
[root@k8s-master mnt]# kubectl get pod
NAME READY STATUS RESTARTS AGE
liveness-httpget-pod 1/1 Running 1 2m41s
myapp-pod 1/1 Running 1 92m
readiness-httpget-pod 1/1 Running 0 22m 说明：删除Html,会发现Pod开始重启了。
[root@k8s-master mnt]# cat live-tcp.yaml
apiVersion: v1
kind: Pod
metadata:
name: probe-tcp
spec:
containers:
- name: nginx
image: wangyanglinux/myapp:v1
livenessProbe:
initialDelaySeconds: 5
timeoutSeconds: 1
tcpSocket:
port: 8080
periodSeconds: 3
[root@k8s-master mnt]#[root@k8s-master mnt]# vim live-tcp.yaml
[root@k8s-master mnt]# kubectl create -f live-tcp.yaml
pod/probe-tcp created
[root@k8s-master mnt]# kubectl get pod
NAME READY STATUS RESTARTS AGE
liveness-httpget-pod 1/1 Running 1 9m24s
myapp-pod 1/1 Running 1 99m
probe-tcp 1/1 Running 0 5s
readiness-httpget-pod 1/1 Running 0 29m
[root@k8s-master mnt]# kubectl get pod
NAME READY STATUS RESTARTS AGE
liveness-httpget-pod 1/1 Running 1 9m37s
myapp-pod 1/1 Running 1 99m
probe-tcp 1/1 Running 1 18s
readiness-httpget-pod 1/1 Running 0 29m
[root@k8s-master mnt]# kubectl get pod
NAME READY STATUS RESTARTS AGE
liveness-httpget-pod 1/1 Running 1 9m41s
myapp-pod 1/1 Running 1 99m
probe-tcp 1/1 Running 1 22s
readiness-httpget-pod 1/1 Running 0 29m
[root@k8s-master mnt]# kubectl get pod
NAME READY STATUS RESTARTS AGE
liveness-httpget-pod 1/1 Running 1 9m43s
myapp-pod 1/1 Running 1 99m
probe-tcp 1/1 Running 1 24s
readiness-httpget-pod 1/1 Running 0 29m
[root@k8s-master mnt]# kubectl get pod
NAME READY STATUS RESTARTS AGE
liveness-httpget-pod 1/1 Running 1 9m44s
myapp-pod 1/1 Running 1 99m
probe-tcp 1/1 Running 1 25s
readiness-httpget-pod 1/1 Running 0 29m
[root@k8s-master mnt]# kubectl get pod
NAME READY STATUS RESTARTS AGE
liveness-httpget-pod 1/1 Running 1 10m
myapp-pod 1/1 Running 1 100m
probe-tcp 1/1 Running 3 47s
readiness-httpget-pod 1/1 Running 0 29m
[root@k8s-master mnt]# kubectl delete -f live-tcp.yaml
pod "probe-tcp" deleted
[root@k8s-master mnt]#说明：删除Html,会发现Pod开始重启了。
Pod hook
Pod hook （钩子）是由 Kubernetes 管理的 kubelet 发起的，当容器中的进程启动前或者容器中的进
程终止之前运行，这是包含在容器的生命周期之中。可以同时为 Pod 中的所有容器都配置 hook
Hook 的类型包括两种：
exec ：执行一段命令
HTTP ：发送 HTTP 请求
重启策略
PodSpec 中有一个 restartPolicy 字段，可能的值为 Always 、 OnFailure 和 Never 。默认为
Always 。 restartPolicy 适用于 Pod 中的所有容器。 restartPolicy 仅指通过同一节点上的
kubelet 重新启动容器。失败的容器由 kubelet 以五分钟为上限的指数退避延迟（ 10 秒， 20 秒， 40
秒 ... ）重新启动，并在成功执行十分钟后重置。如 Pod 文档 中所述，一旦绑定到一个节点， Pod 将
永远不会重新绑定到另一个节点。
Pod phase
Pod 的 status 字段是一个 PodStatus 对象， PodStatus 中有一个 phase 字段。
Pod 的相位（ phase ）是 Pod 在其生命周期中的简单宏观概述。该阶段并不是对容器或 Pod 的综合汇总，也不是为了做为综合状态机
Pod 相位的数量和含义是严格指定的。除了本文档中列举的状态外，不应该再假定 Pod 有其他的phase 值
几种常见的值
- 挂起（ Pending ）： Pod 已被 Kubernetes 系统接受，但有一个或者多个容器镜像尚未创建。等待时间包括调度 Pod 的时间和通过网络下载镜像的时间，这可能需要花点时间
- 运行中（ Running ）：该 Pod 已经绑定到了一个节点上， Pod 中所有的容器都已被创建。至少有一个容器正在运行，或者正处于启动或重启状态
- 成功（ Succeeded ）： Pod 中的所有容器都被成功终止，并且不会再重启
- 失败（ Failed ）： Pod 中的所有容器都已终止了，并且至少有一个容器是因为失败终止。也就是说，容器以非 0 状态退出或者被系统终止
- 未知（ Unknown ）：因为某些原因无法取得 Pod 的状态，通常是因为与 Pod 所在主机通信失败
[root@k8s-master mnt]# vim post.yaml
[root@k8s-master mnt]# kubectl create -f post.yaml
pod/lifecycle-demo created
[root@k8s-master mnt]# kubectl get pod
NAME READY STATUS RESTARTS AGE
lifecycle-demo 1/1 Running 0 9s
liveness-httpget-pod 1/1 Running 1 40m
myapp-pod 1/1 Running 1 130m
readiness-httpget-pod 1/1 Running 0 60m
[root@k8s-master mnt]# kubectl exec lifecycle-demo -it -- /bin/bash
OCI runtime exec failed: exec failed: container_linux.go:346: starting container process caused "exec: \"/bin/bash\": stat /bin/bash: no such file or directory": unknown
command terminated with exit code 126
[root@k8s-master mnt]# kubectl exec lifecycle-demo -it -- /bin/sh
/ # cd /usr/share/message
/bin/sh: cd: can't cd to /usr/share/message
/ # cat /usr/share/message
Hello from the postStart handler
/ # exit
[root@k8s-master mnt]# cat post.yaml
apiVersion: v1
kind: Pod
metadata:
name: lifecycle-demo
spec:
containers:
- name: lifecycle-demo-container
image: wangyanglinux/myapp:v1
lifecycle:
postStart:
exec:
command: ["/bin/sh", "-c", "echo Hello from the postStart handler > /usr/share/message"]
preStop:
exec:
command: ["/bin/sh", "-c", "echo Hello from the poststop handler > /usr/share/message"]
[root@k8s-master mnt]#原文链接：http://dwz.date/MMr