四、Kubernetes—资源清单
目录
一、K8S中的资源
1、资源的定义
2、资源的种类
二、资源清单
1、简单说明
2、YAML支持的数据结构
三、常用字段解释说明
1、必须存在的属性
2、主要对象
3、额外的参数项
四、容器生命周期
1、 Init容器
2、Init容器的作用
3、使用Init的案例
5、容器探针
6、容器启动、退出动作
7、其它
一、K8S中的资源
1、资源的定义
K8S中所有的内容都抽象为资源，资源实例化后，被称为对象。
2、资源的种类
- 工作负载型资源（workload）：Pod、ReplicaSet、Deployment、StatefulSet、DaemonSet、Job、CronJob（ReplicationController在v1.11版本被废弃）
- 服务发现及负载均衡型资源（ServiceDiscovery LoadBalance）：Service、Ingress、...
- 配置与存储型资源：Volume（存储卷）、CSI（容器存储接口，可以扩展各种各样的第三方存储卷）
- 特殊类型的存储卷：ConfigMap（当配置中心来使用的资源类型）、Secret（保存敏感数据）、DownwardAPI（把外部环境中的信息输出给容器）
- 集群级资源：Namespace、Node、Role、ClusterRole、RoleBinding、ClusterRoleBinding
- 云数据型资源：HPA、PodTemplate、LimitRange
二、资源清单
在K8S中，一般使用yaml格式的文件来创建符合我们预期期望的pod，这样的yaml文件我们一般称为资源清单。关于yaml语法，下面简单的介绍下
1、简单说明
是一个可读性高，用来表达数据序列的格式。YAML的意思其实是：仍是一种标记语言，但为了强调这种语言以数据做为中心，而不是以标记语言为重点。
基本语法
- 缩进时不允许使用Tab键，只允许使用空格
- 缩进的空格数目不重要，只要相同层级的元素左侧对齐即可
- #标识注释，从这个字符一直到行尾，都会被解释器忽略
2、YAML支持的数据结构
- 对象：键值对的集合，又称为映射（mapping）/哈希（hashes）/字典（dictionary）
- 数组：一组按次序排列的值，又称为序列（sequence）/列表（list）
- 纯量（scalars）：单个的，不可再分的值
1）对象类型：对象的一组键值对，使用冒号结构表示
name: Steve
age: 18Yaml也允许另一种写法，将所有键值对写成一个行内对象
hash: { name: Steve, age: 18 }2）数组类型：一组连词线开头的行，构成一个数组
animal
- Cat
- Dog数组也可以采用行内表示法
animal: [Cat, Dog]复合结构：对象和数组可以结合使用，形成复合结构
languages：
- Ruby
- Perl
- Python
websites：
YAML: yaml.org
Ruby: ruby-lang.org
Python: python.org
Perl: use.perl.org字符串
字符串默认不适用引号表示
str: 这是一行字符串如果字符串之中包含空格或特殊字符，需要放在引号之中
str: '内容': 字符串'单引号和双引号都可以使用，双引号不会对特殊字符转义
s1: '内容\n字符串'
s2: '内容\n字符串'单引号之中如果还有单引号，需要连续使用两个单引号转义
str: 'labor''s day'字符串可以写成多行，从第二行开始，必须有一个单空格缩进。换行符会被转成空格
str: 这是一段
多行
字符串三、常用字段解释说明
在k8s中，可以通过命令查看相应资源的属性情况
[root@k8s-master ~]# kubectl explain pod
KIND: Pod
VERSION: v1
DESCRIPTION:
Pod is a collection of containers that can run on a host. This resource is
created by clients and scheduled onto hosts.
FIELDS:
apiVersion
APIVersion defines the versioned schema of this representation of an
object. Servers should convert recognized schemas to the latest internal
value, and may reject unrecognized values. More info:
https://git.k8s.io/community/contributors/devel/sig-architecture/api-conventions.md#resources
kind
Kind is a string value representing the REST resource this object
represents. Servers may infer this from the endpoint the client submits
requests to. Cannot be updated. In CamelCase. More info:
https://git.k8s.io/community/contributors/devel/sig-architecture/api-conventions.md#types-kinds
metadata 如果继续想查看资源下一字段的属性可以继续使用命令
[root@k8s-master ~]# kubectl explain pod.apiVersion
KIND: Pod
VERSION: v1
FIELD: apiVersion
DESCRIPTION:
APIVersion defines the versioned schema of this representation of an
object. Servers should convert recognized schemas to the latest internal
value, and may reject unrecognized values. More info:
https://git.k8s.io/community/contributors/devel/sig-architecture/api-conventions.md#resources
1、必须存在的属性
2、主要对象
3、额外的参数项
下面就以创建一个pod为例，简单介绍下如果利用yaml文件创建资源对象
首先，编写yaml文件
[root@k8s-master pod]# vim pod.yaml
# 此处故意利用同一个镜像创建两个容器，来验证同一个pod下共享网络栈
apiVersion: v1
kind: Pod
metadata:
name: myapp-pod
labels:
app: myapp
spec:
containers:
- name: app
image: hushensong.com/library/myapp:v1
- name: test
image: hushensong.com/library/myapp:v1
[root@k8s-master pod]# kubectl apply -f pod.yaml
pod/myapp-pod created
[root@k8s-master pod]#
[root@k8s-master pod]#
[root@k8s-master pod]# kubectl get pod
NAME READY STATUS RESTARTS AGE
myapp-pod 1/2 Error 1 11s
查看pod的状态时，pod状态异常，查看pod运行详细信息，发现test容器异常
[root@k8s-master pod]# kubectl describe pod myapp-pod
Name: myapp-pod
Namespace: default
Priority: 0
Node: k8s-node02/192.168.221.133
Start Time: Sun, 14 Mar 2021 22:54:53 +0800
Labels: app=myapp
Annotations: Status: Running
IP: 10.244.2.3
IPs:
IP: 10.244.2.3
Containers:
app:
Container ID: docker://d890fad5c335493db2a133a9cebc6298fd49023e19a1df6e32a2d6d99f054176
Image: hushensong.com/library/myapp:v1
Image ID: docker-pullable://hushensong.com/library/myapp@sha256:9eeca44ba2d410e54fccc54cbe9c021802aa8b9836a0bcf3d3229354e4c8870e
Port:
Host Port:
State: Running
Started: Sun, 14 Mar 2021 22:54:54 +0800
Ready: True
Restart Count: 0
Environment:
Mounts:
/var/run/secrets/kubernetes.io/serviceaccount from default-token-9ktlc (ro)
test:
Container ID: docker://cb029d05f56c45adbc410171291b4b83be56d9b9704230f5a94c197b8cb0eff8
Image: hushensong.com/library/myapp:v1
Image ID: docker-pullable://hushensong.com/library/myapp@sha256:9eeca44ba2d410e54fccc54cbe9c021802aa8b9836a0bcf3d3229354e4c8870e
Port:
Host Port:
State: Waiting
Reason: CrashLoopBackOff
Last State: Terminated
Reason: Error
Exit Code: 1
Started: Sun, 14 Mar 2021 22:56:27 +0800
Finished: Sun, 14 Mar 2021 22:56:29 +0800
Ready: False
Restart Count: 4
Environment:
Mounts:
/var/run/secrets/kubernetes.io/serviceaccount from default-token-9ktlc (ro)
Conditions:
Type Status
Initialized True
Ready False
ContainersReady False
PodScheduled True
Volumes:
default-token-9ktlc:
Type: Secret (a volume populated by a Secret)
SecretName: default-token-9ktlc
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/myapp-pod to k8s-node02
Normal Pulled 115s kubelet, k8s-node02 Container image "hushensong.com/library/myapp:v1" already present on machine
Normal Created 115s kubelet, k8s-node02 Created container app
Normal Started 115s kubelet, k8s-node02 Started container app
Normal Pulled 22s (x5 over 115s) kubelet, k8s-node02 Container image "hushensong.com/library/myapp:v1" already present on machine
Normal Created 22s (x5 over 115s) kubelet, k8s-node02 Created container test
Normal Started 22s (x5 over 115s) kubelet, k8s-node02 Started container test
Warning BackOff 19s (x7 over 109s) kubelet, k8s-node02 Back-off restarting failed container
看看具体容器的日志信息，提示端口占用，证明同一个pod中共享网络栈
[root@k8s-master pod]# kubectl logs pod myapp-pod -c test
Error from server (NotFound): pods "pod" not found
[root@k8s-master pod]# kubectl logs myapp-pod -c test
2021/03/14 14:56:27 [emerg] 1#1: bind() to 0.0.0.0:80 failed (98: Address in use)
nginx: [emerg] bind() to 0.0.0.0:80 failed (98: Address in use)
2021/03/14 14:56:27 [emerg] 1#1: bind() to 0.0.0.0:80 failed (98: Address in use)
nginx: [emerg] bind() to 0.0.0.0:80 failed (98: Address in use)
2021/03/14 14:56:27 [emerg] 1#1: bind() to 0.0.0.0:80 failed (98: Address in use)
nginx: [emerg] bind() to 0.0.0.0:80 failed (98: Address in use)
2021/03/14 14:56:27 [emerg] 1#1: bind() to 0.0.0.0:80 failed (98: Address in use)
nginx: [emerg] bind() to 0.0.0.0:80 failed (98: Address in use)
2021/03/14 14:56:27 [emerg] 1#1: bind() to 0.0.0.0:80 failed (98: Address in use)
nginx: [emerg] bind() to 0.0.0.0:80 failed (98: Address in use)
2021/03/14 14:56:27 [emerg] 1#1: still could not bind()
nginx: [emerg] still could not bind()
删除pod.yaml文件中容器内容，然后删除刚刚创建的pod，重新创建，显示成功
[root@k8s-master pod]# kubectl delete pod myapp-pod
pod "myapp-pod" deleted
[root@k8s-master pod]# kubectl create -f pod.yaml
pod/myapp-pod created
[root@k8s-master pod]# kubectl get pod
NAME READY STATUS RESTARTS AGE
myapp-pod 1/1 Running 0 5s
[root@k8s-master pod]# kubectl get pod -o wide
NAME READY STATUS RESTARTS AGE IP NODE NOMINATED NODE READINESS GATES
myapp-pod 1/1 Running 0 13s 10.244.1.2 k8s-node01
[root@k8s-master pod]# curl 10.244.1.2
Hello MyApp | Version: v1 | Pod Name 四、容器生命周期
1、 Init容器
Pod能够具有多个容器，应用运行在容器里面，但是它也可能有一个或多个先于应用容器启动的Init容器。
Init容器于普通的容器非常像，除了如下两点：
- Init容器总是运行到成功完成为止
- 每个Init容器都必须在下一个Init容器启动之前成功完成
如果Pod的Init容器失败，Kubernetes会不断的重启该pod，知道Init容器成功为止。然而，如果Pod对应的restartPolicy为Never，它不会重新启动。
2、Init容器的作用
因为Init容器具有与应用程序容器分离的单独镜像，所以它们的启动相关代码具有如下优势：
它们可以包含并运行实用工具，但是出于安全考虑，是不建议在应用程序容器镜像中包含这些实用工具的。
它们可以包含实用工具和定制化代码来安装，但是不能出现在应用程序镜像中。例如，创建镜像没必要FROM另一个镜像，只需要在安装过程中使用类似sed、awk、Python或dig这样的工具。
应用程序镜像可以分离出创建和部署的角色，而没有必要联合它们构建一个单独的镜像。
Init容器使用Linux Namespace，所以相对应用程序容器来说具有不同的文件系统视图。因此，它们能够具有访问Secret的权限，而应用程序容器则不能。
它们必须在应用程序容器启动之前运行完成，而应用程序容器是并行运行的，所以Init容器能够提供了一个简单的阻塞或延迟应用容器的启动的方法，直到满足了一组先决条件。
3、使用Init的案例
首先在工作节点下载busybox镜像，并打标签，防止每次都拉取最新latest镜像
[root@k8s-node02 ~]# docker pull busybox
[root@k8s-node02 ~]# docker tag busybox:latest busybox:v1
[root@k8s-node02 ~]# docker rmi busybox:latest
Untagged: busybox:latest
编写pod.yaml
apiVersion: v1
kind: Pod
metadata:
name: myapp-pod
labels:
app: myapp
spec:
containers:
- name: myapp-container
image: busybox:v1
command: ['sh','-c','echo The app is running! && sleep 3600']
initContainers:
- name: init-myservice
image: busybox
command: ['sh','-c','until nslookup myservice; do echo waiting for myservice; sleep 2; done;']
- name: init-mydb
image: busybox
command: ['sh','-c','until nslookup mydb; do echo waiting for mydb; sleep 2; done;']
[root@k8s-master pod]# kubectl create -f pod.yaml
pod/myapp-pod created
#查看状态为初始镜像在执行
[root@k8s-master pod]# kubectl get pod
NAME READY STATUS RESTARTS AGE
myapp-pod 0/1 Init:0/2 0 31s
# 查看pod详细信息，发现在启动init-myservice
[root@k8s-master pod]# kubectl describe pod myapp-pod
Name: myapp-pod
Namespace: default
Priority: 0
Node: k8s-node02/192.168.221.133
Start Time: Mon, 15 Mar 2021 16:47:30 +0800
Labels: app=myapp
Annotations:
Status: Pending
IP: 10.244.2.4
IPs:
IP: 10.244.2.4
Init Containers:
init-myservice:
Container ID: docker://d7929095d3df6851e846687051edb361c39d07459018c75ed8c630035b4029e4
Image: busybox
Image ID: docker-pullable://busybox@sha256:ce2360d5189a033012fbad1635e037be86f23b65cfd676b436d0931af390a2ac
Port:
Host Port:
Command:
sh
-c
until nslookup myservice; do echo waiting for myservice; sleep 2; done;
State: Running
Started: Mon, 15 Mar 2021 16:47:35 +0800
Ready: False
Restart Count: 0
Environment:
Mounts:
/var/run/secrets/kubernetes.io/serviceaccount from default-token-9ktlc (ro)
init-mydb:
Container ID:
Image: busybox
Image ID:
Port:
Host Port:
Command:
sh
-c
until nslookup mydb; do echo waiting for mydb; sleep 2; done;
State: Waiting
Reason: PodInitializing
Ready: False
Restart Count: 0
Environment:
Mounts:
/var/run/secrets/kubernetes.io/serviceaccount from default-token-9ktlc (ro)
Containers:
myapp-container:
Container ID:
Image: busybox:v1
Image ID:
Port:
Host Port:
Command:
sh
-c
echo The app is running! && sleep 3600
State: Waiting
Reason: PodInitializing
Ready: False
Restart Count: 0
Environment:
Mounts:
/var/run/secrets/kubernetes.io/serviceaccount from default-token-9ktlc (ro)
Conditions:
Type Status
Initialized False
Ready False
ContainersReady False
PodScheduled True
Volumes:
default-token-9ktlc:
Type: Secret (a volume populated by a Secret)
SecretName: default-token-9ktlc
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/myapp-pod to k8s-node02
Normal Pulling 112s kubelet, k8s-node02 Pulling image "busybox"
Normal Pulled 108s kubelet, k8s-node02 Successfully pulled image "busybox"
Normal Created 108s kubelet, k8s-node02 Created container init-myservice
Normal Started 108s kubelet, k8s-node02 Started container init-myservice
#查看容器日志信息查出问题
[root@k8s-master pod]# kubectl logs myapp-pod -c init-myservice
Server: 10.96.0.10
Address: 10.96.0.10:53
** server can't find myservice.default.svc.cluster.local: NXDOMAIN
*** Can't find myservice.svc.cluster.local: No answer
*** Can't find myservice.cluster.local: No answer
*** Can't find myservice.localdomain: No answer
*** Can't find myservice.default.svc.cluster.local: No answer
*** Can't find myservice.svc.cluster.local: No answer
*** Can't find myservice.cluster.local: No answer
*** Can't find myservice.localdomain: No answer 创建myservice.yaml创建service服务
[root@k8s-master pod]# vim myservice.yaml
apiVersion: v1
kind: Service
metadata:
name: myservice
spec:
ports:
- protocol: TCP
port: 80
targetPort: 9376
[root@k8s-master pod]# kubectl create -f myservice.yaml
service/myservice created
[root@k8s-master pod]# kubectl get svc
NAME TYPE CLUSTER-IP EXTERNAL-IP PORT(S) AGE
kubernetes ClusterIP 10.96.0.1 443/TCP 7d
myservice ClusterIP 10.104.126.83 80/TCP 2m33s
[root@k8s-master pod]# kubectl get pod -n kube-system
NAME READY STATUS RESTARTS AGE
coredns-66bff467f8-rwxx2 1/1 Running 5 7d
coredns-66bff467f8-t9ztd 1/1 Running 5 7d
etcd-k8s-master 1/1 Running 5 7d
kube-apiserver-k8s-master 1/1 Running 5 7d
kube-controller-manager-k8s-master 1/1 Running 5 7d
kube-flannel-ds-7kmrb 1/1 Running 5 7d
kube-flannel-ds-cg77h 1/1 Running 5 7d
kube-flannel-ds-jpphf 1/1 Running 5 7d
kube-proxy-8b4bj 1/1 Running 5 7d
kube-proxy-kx9fw 1/1 Running 5 7d
kube-proxy-tb2hw 1/1 Running 5 7d
kube-scheduler-k8s-master 1/1 Running 5 7d
#再次查看发现初始化容器已就绪了一个
[root@k8s-master pod]# kubectl get pod
NAME READY STATUS RESTARTS AGE
myapp-pod 0/1 Init:1/2 0 15m
创建mydb.yaml创建service服务
[root@k8s-master pod]# vim mydb.yaml
apiVersion: v1
kind: Service
metadata:
name: mydb
spec:
ports:
- protocol: TCP
port: 80
targetPort: 9377
# 再次查看pod的状态时已经处于正常Running 状态
[root@k8s-master pod]# kubectl create -f mydb.yaml
[root@k8s-master pod]# kubectl get pod
NAME READY STATUS RESTARTS AGE
myapp-pod 1/1 Running 0 21m特殊说明
- 在Pod启动过程中，Init容器会按顺序在网络和数据卷初始化之后启动。每个容器必须在下一个容器启动之前成功退出。
- 如果由于运行时或失败退出，将导致容器启动失败，它会根据Pod的restartPolicy指定的策略进行重试。然而，如果Pod的restartPolicy设置为Always，Init容器失败时会使用RestartPolicy策略。
- 在所有的Init容器没有成功之前，Pod将不会变成Ready状态。Init容器的端口将不会在service中进行聚集。正在初始化中的Pod处于Pending状态，但应该会将Initializing状态设置为true。
- 如果Pod重启，所有Init容器必须重新执行。
- # 对Init容器spec的修改被限制在容器image字段，修改其他字段都不会生效。更改Init容器的image字段，等价于重启该Pod。
- Init容器具有应用容器的所有字段。除了readinessProbe，因为Init容器无法定义不同于完成（completion）的就绪（readiness）之外的其他状态。这会在验证过程中强制执行。
- 在Pod中的每个app和Init容器的名称必须唯一；与任何其他容器共享同一个名称，会在验证时抛出错误。
5、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。
每次探针都将获得以下三个结果之一：
- 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。
下面就给大家演示就绪检测实例readinessProbe-httpget：
创建pod的read.yaml文件
[root@k8s-master pod]# vim read.yaml
apiVersion: v1
kind: Pod
metadata:
name: readiness-httpget-pod
namespace: default
spec:
containers:
- name: readiness-httpget-container
image: hushensong.com/library/myapp:v1
imagePullPolicy: IfNotPresent
readinessProbe:
httpGet:
port: 80
path: /index1.html
initialDelaySeconds: 1
periodSeconds: 3
#状态为Running 但是没有准备
[root@k8s-master pod]# kubectl get pod
NAME READY STATUS RESTARTS AGE
readiness-httpget-pod 0/1 Running 0 104s
#查看原因
[root@k8s-master pod]# kubectl describe pod readiness-httpget-pod
Name: readiness-httpget-pod
Namespace: default
Priority: 0
Node: k8s-node01/192.168.221.132
Start Time: Mon, 15 Mar 2021 21:33:14 +0800
Labels:
Annotations:
Status: Running
IP: 10.244.1.4
IPs:
IP: 10.244.1.4
Containers:
readiness-httpget-container:
Container ID: docker://7a6d229e97a6f1a2dc57d6c4feb6cc809f6a5dfa6c43ac8f9e4a36e7ce0993aa
Image: hushensong.com/library/myapp:v1
Image ID: docker-pullable://hushensong.com/library/myapp@sha256:9eeca44ba2d410e54fccc54cbe9c021802aa8b9836a0bcf3d3229354e4c8870e
Port:
Host Port:
State: Running
Started: Mon, 15 Mar 2021 21:33:15 +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-9ktlc (ro)
Conditions:
Type Status
Initialized True
Ready False
ContainersReady False
PodScheduled True
Volumes:
default-token-9ktlc:
Type: Secret (a volume populated by a Secret)
SecretName: default-token-9ktlc
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 4m32s kubelet, k8s-node01 Container image "hushensong.com/library/myapp:v1" already present on machine
Normal Created 4m32s kubelet, k8s-node01 Created container readiness-httpget-container
Normal Started 4m32s kubelet, k8s-node01 Started container readiness-httpget-container
Warning Unhealthy 3m26s (x22 over 4m29s) kubelet, k8s-node01 Readiness probe failed: HTTP probe failed with statuscode: 404
#进入容器，增加探测文件
[root@k8s-master pod]# kubectl get pod
NAME READY STATUS RESTARTS AGE
readiness-httpget-pod 0/1 Running 0 5m35s
[root@k8s-master pod]# kubectl exec readiness-httpget-pod -it -- /bin/sh
/usr/share/nginx/html # ls
50x.html index.html
/usr/share/nginx/html # echo "hello" >> index1.html
#再次查看pod状态，此时变为正常Ready
[root@k8s-master pod]# kubectl get pod
NAME READY STATUS RESTARTS AGE
readiness-httpget-pod 1/1 Running 0 8m13s
接下来给大家演示下探针存活检测livenessProbe-exec：
创建Pod的live-exec.yaml文件
[root@k8s-master pod]# vim live-exec.yaml
apiVersion: v1
kind: Pod
metadata:
name: liveness-exec-pod
namespace: default
spec:
containers:
- name: liveness-exec-container
image: busybox:v1
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 pod]# kubectl create -f live-exec.yaml
pod/liveness-exec-pod created
[root@k8s-master pod]# kubectl get pod
NAME READY STATUS RESTARTS AGE
liveness-exec-pod 1/1 Running 0 7s
#pod的状态正常，但是过了60s后，文件不存在了将对pod进行重启
[root@k8s-master pod]# kubectl get pod
NAME READY STATUS RESTARTS AGE
liveness-exec-pod 1/1 Running 1 2m6s
接下来给大家演示下探针存活检测livenessProbe-httpget：
[root@k8s-master pod]# vim live-http.yaml
apiVersion: v1
kind: Pod
metadata:
name: liveness-httpget-pod
namespace: default
spec:
containers:
- name: liveness-httpget-container
image: hushensong.com/library/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 pod]# kubectl create -f live-http.yaml
pod/liveness-httpget-pod created
[root@k8s-master pod]# kubectl get pod -o wide
NAME READY STATUS RESTARTS AGE IP NODE NOMINATED NODE READINESS GATES
liveness-httpget-pod 1/1 Running 0 45s 10.244.2.5 k8s-node02
[root@k8s-master pod]# curl 10.244.2.5/index.html
Hello MyApp | Version: v1 | Pod Name
#删除文件后，无法访问，此时会对pod进行重启，重启后可再次访问
[root@k8s-master pod]# kubectl exec liveness-httpget-pod -it -- rm -rf /usr/share/nginx/html/index.html
[root@k8s-master pod]# curl 10.244.2.5/index.html
404 Not Found
404 Not Found
nginx/1.12.2
[root@k8s-master pod]# kubectl get pod
NAME READY STATUS RESTARTS AGE
liveness-httpget-pod 1/1 Running 3 4m36s
[root@k8s-master pod]# curl 10.244.2.5/index.html
Hello MyApp | Version: v1 | Pod Name
接下来给大家演示下探针存活检测livenessProbe-tcp：
创建pod的live-tcp.yaml文件
[root@k8s-master pod]# vim live-tcp.yaml
apiVersion: v1
kind: Pod
metadata:
name: probe-tcp
spec:
containers:
- name: nginx
image: hushensong.com/library/myapp:v1
livenessProbe:
initialDelaySeconds: 5
timeoutSeconds: 1
tcpSocket:
port: 8080
periodSeconds: 3
#在配置yaml文件是故意将探测端口设置成错误的8080端口，pod将重启
[root@k8s-master pod]# kubectl create -f live-tcp.yaml
pod/probe-tcp created
[root@k8s-master pod]# kubectl get pod
NAME READY STATUS RESTARTS AGE
probe-tcp 1/1 Running 3 46s
[root@k8s-master pod]# kubectl get pod
NAME READY STATUS RESTARTS AGE
probe-tcp 0/1 CrashLoopBackOff 4 114s
[root@k8s-master pod]# kubectl describe pod probe-tcp
Name: probe-tcp
Namespace: default
Priority: 0
Node: k8s-node01/192.168.221.132
Start Time: Mon, 15 Mar 2021 22:21:57 +0800
Labels:
Annotations:
Status: Running
IP: 10.244.1.6
IPs:
IP: 10.244.1.6
Containers:
nginx:
Container ID: docker://87517c2bab24a54a3d674f2c5162f826b01919c52f2ac242e4f6eef1a6cfb314
Image: hushensong.com/library/myapp:v1
Image ID: docker-pullable://hushensong.com/library/myapp@sha256:9eeca44ba2d410e54fccc54cbe9c021802aa8b9836a0bcf3d3229354e4c8870e
Port:
Host Port:
State: Waiting
Reason: CrashLoopBackOff
Last State: Terminated
Reason: Completed
Exit Code: 0
Started: Mon, 15 Mar 2021 22:24:01 +0800
Finished: Mon, 15 Mar 2021 22:24:12 +0800
Ready: False
Restart Count: 5
Liveness: tcp-socket :8080 delay=5s timeout=1s period=3s #success=1 #failure=3
Environment:
Mounts:
/var/run/secrets/kubernetes.io/serviceaccount from default-token-9ktlc (ro)
Conditions:
Type Status
Initialized True
Ready False
ContainersReady False
PodScheduled True
Volumes:
default-token-9ktlc:
Type: Secret (a volume populated by a Secret)
SecretName: default-token-9ktlc
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/probe-tcp to k8s-node01
Normal Pulled 2m53s (x4 over 3m29s) kubelet, k8s-node01 Container image "hushensong.com/library/myapp:v1" already present on machine
Normal Created 2m53s (x4 over 3m29s) kubelet, k8s-node01 Created container nginx
Normal Started 2m53s (x4 over 3m29s) kubelet, k8s-node01 Started container nginx
Normal Killing 2m53s (x3 over 3m17s) kubelet, k8s-node01 Container nginx failed liveness probe, will be restarted
Warning Unhealthy 2m47s (x10 over 3m23s) kubelet, k8s-node01 Liveness probe failed: dial tcp 10.244.1.6:8080: connect: connection refused
探针就绪检测和存活检测是可以同时配置在文件中的，如下演示所示：
[root@k8s-master pod]# vim live-httpget-pod.yaml
apiVersion: v1
kind: Pod
metadata:
name: liveness-httpget-pod
namespace: default
spec:
containers:
- name: liveness-httpget-container
image: hushensong.com/library/myapp:v1
imagePullPolicy: IfNotPresent
ports:
- name: http
containerPort: 80
readinessProbe:
httpGet:
port: 80
path: /index1.html
initialDelaySeconds: 1
periodSeconds: 3
livenessProbe:
httpGet:
port: http
path: /index.html
initialDelaySeconds: 1
periodSeconds: 3
timeoutSeconds: 10
[root@k8s-master pod]# kubectl create -f live-httpget-pod.yaml
pod/liveness-httpget-pod created
[root@k8s-master pod]# kubectl get pod
NAME READY STATUS RESTARTS AGE
liveness-httpget-pod 0/1 Running 0 16s
[root@k8s-master pod]# kubectl exec liveness-httpget-pod -it -- /bin/sh
/ # cd /usr/share/nginx/html/
/usr/share/nginx/html # ls
50x.html index.html
/usr/share/nginx/html # echo "123" > index1.html
[root@k8s-master pod]# kubectl get pod
NAME READY STATUS RESTARTS AGE
liveness-httpget-pod 1/1 Running 0 92s
[root@k8s-master pod]# kubectl exec liveness-httpget-pod -it -- rm -rf /usr/share/nginx/html/index.html
[root@k8s-master pod]# kubectl get pod -w
NAME READY STATUS RESTARTS AGE
liveness-httpget-pod 1/1 Running 0 2m26s
liveness-httpget-pod 0/1 Running 1 2m28s
说明：在就绪检测时，由于没有index1.yaml文件，所以READY一直未为0，创建index1.html文件后，pod状态正常，当删除文件index.html后，存活检测失败，对pod进行重启
6、容器启动、退出动作
[root@k8s-master pod]# vim post.yaml
apiVersion: v1
kind: Pod
metadata:
name: lifecycle-demo
spec:
containers:
- name: lifecycle-demo-container
image: hushensong.com/library/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 pod]# kubectl create -f post.yaml
pod/lifecycle-demo created
[root@k8s-master pod]# kubectl get pod
NAME READY STATUS RESTARTS AGE
lifecycle-demo 1/1 Running 0 6s
[root@k8s-master pod]# kubectl exec lifecycle-demo -it -- /bin/sh
/ # cat /usr/share/message
Hello from the postStart Handler说明：在启动时在/usr/share/mesage中增加内容。
7、其它
1）hook
Pod hook（钩子）时有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
2）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。
3）pod相位（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。
那么phase有哪些可能存在的状态呢
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所在的主机通信失败。
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