Kubernetes 学习总结(3) M

发布时间：2019-09-22 07:46:44编辑：auto阅读（1469）

APIserver符合RESTful风格，支持GET/PUT/DELETE/POST等各种操作。所以也支持kubectl通过一系列命令对各处资源进行管理控制。
常用的资源
1)、workLoad(工作负载型资源，运行APP，对外提供服务): Pod/ReplicaSet/Deployment/ StatefulSet/ DaemonSet/ Job/ Cronjob /
2)、service discovery and Load Balance(服务发现及均衡型资源)：Service/ Ingress
3)、configuration and storage(配置与存储类型资源) ：Volume,CSI(容器存储接口，扩展第三方的存储)
ConfigMap，Secret(特殊的配置类型资源)
Downward API(配置类型资源)
4)、集群级资源(配置在名称空间级别)： namespace, node, role, clusterRole, roleBinding, clusterRoleBinding
5)、元数据类型资源：HPA、PodTemplate、limitRange（读取权限)

一、配置清单(configuration mainfest)
kubectl 通常通过ymal格式的配置清单对资源进行管理控制。APIserver仅处理Json格式定义的资源定义。ymal格式的配置清单由APIserver自动将其转为json格式，而后再提交处理。
[root@docker79 ~]# kubectl get deployment
NAME DESIRED CURRENT UP-TO-DATE AVAILABLE AGE
nginx-deploy 2 2 2 2 1d
[root@docker79 ~]# kubectl get deployment nginx-deploy -o yaml (查看nginx-deploy的配置清单)
配置清单主格式如下
apiVersion: group/version (如果group省略表示core组)
kind: Pod (资源类型)
metadata: 元数据
spec: 期望状态 disired state
status: 当前状态， current state ，本字段由kubernetes 集群维护;

[root@docker79 ~]# kubectl api-versions (查看默认支持的group与version)

admissionregistration.k8s.io/v1beta1
apiextensions.k8s.io/v1beta1
apiregistration.k8s.io/v1
apiregistration.k8s.io/v1beta1
apps/v1
apps/v1beta1
apps/v1beta2
authentication.k8s.io/v1
authentication.k8s.io/v1beta1
authorization.k8s.io/v1
authorization.k8s.io/v1beta1
autoscaling/v1
autoscaling/v2beta1
batch/v1
batch/v1beta1
certificates.k8s.io/v1beta1
events.k8s.io/v1beta1
extensions/v1beta1
networking.k8s.io/v1
policy/v1beta1
rbac.authorization.k8s.io/v1
rbac.authorization.k8s.io/v1beta1
scheduling.k8s.io/v1beta1
storage.k8s.io/v1
storage.k8s.io/v1beta1
v1

[root@docker79 ~]#

kubectl explain
kubectl explain Resource_Kind[.Subitem...] 查看相关resource 在定义配置清单时的帮助信息。在帮助信息中常见格式如下：
apiVersion <string> 表示字符串类型
metadata <Object> 表示需要嵌套多层字段
labels <map[string]string> 表示由k:v组成的映射
finalizers <[]string> 表示字串列表
ownerReferences <[]Object> 表示对象列表

资源清单 例1：
[root@docker79 ~]# mkdir manifests
[root@docker79 ~]# cd manifests/
[root@docker79 manifests]# vim pod-demo.yaml
[root@docker79 manifests]# cat pod-demo.yaml

apiVersion: v1
kind: Pod
metadata:
  name: pod-demo
  namespace: default
  labels:
    app: nginx
    tier: frontend
spec:
  containers:
  - name: nginx
    image: nginx:1-alpine
  - name: busybox
    image: busybox:latest
    command:
    - "/bin/sh"
    - "-c"
    - "sleep 3600"

[root@docker79 manifests]# kubectl create -f pod-demo.yaml
pod/pod-demo created
[root@docker79 manifests]# kubectl get pods
NAME READY STATUS RESTARTS AGE
pod-demo 2/2 Running 0 8s
[root@docker79 manifests]# kubectl get pods -o wide
NAME READY STATUS RESTARTS AGE IP NODE NOMINATED NODE
pod-demo 2/2 Running 0 17s 10.244.1.9 docker78 <none>
[root@docker79 manifests]#
[root@docker79 manifests]# kubectl logs pod-demo busybox
[root@docker79 manifests]# kubectl logs pod-demo nginx
[root@docker79 manifests]# kubectl exec -it pod-demo -c busybox -- /bin/sh
/ # netstat -tnlp
Active Internet connections (only servers)
Proto Recv-Q Send-Q Local Address Foreign Address State PID/Program name
tcp 0 0 0.0.0.0:80 0.0.0.0:* LISTEN -
/ # exit
[root@docker79 manifests]# kubectl delete -f pod-demo.yaml
pod "pod-demo" deleted
[root@docker79 manifests]#

再次修改资源清单，例2：
[root@docker79 manifests]# vim pod-demo.yaml
[root@docker79 manifests]# cat pod-demo.yaml

apiVersion: v1
kind: Pod
metadata:
  name: pod-demo
  namespace: default
  labels:
    app: nginx
    tier: frontend
spec:
  containers:
  - name: nginx
    image: nginx:1-alpine
    imagePullPolicy: IfNotPresent
    ports:
    - containerPort: 80
      name: http
    - name: https
      containerPort: 443

[root@docker79 manifests]# kubectl apply -f pod-demo.yaml
pod/pod-demo created
[root@docker79 manifests]# kubectl get pods
NAME READY STATUS RESTARTS AGE
pod-demo 1/1 Running 0 6s
[root@docker79 manifests]# kubectl get pods -o wide
NAME READY STATUS RESTARTS AGE IP NODE NOMINATED NODE
pod-demo 1/1 Running 0 14s 10.244.1.10 docker78 <none>
[root@docker79 manifests]#
说明：imagePullPolicy: <string> 有三个值，分别是 Always ，Never，IfNotPresent （如果标签是latest，默认策略为Always) ，一项创建本项不能更新。
ports 选项可参考：kubectl explain pod.spec.containers.ports

二、Labels、Selector及 Annotation
Lables 是 key=value 格式的键值对儿。key最大长度 63字符，只能以字母或数字开头，由字母、数字、-、_、. 组成。value 最大长度 63字符，可以为空。标签支持前缀，但不能超出253字符(一般都是name或FQDN)
[root@docker79 manifests]# kubectl get pods --show-labels
NAME READY STATUS RESTARTS AGE LABELS
pod-demo 1/1 Running 0 14m app=nginx,tier=frontend
[root@docker79 manifests]# kubectl get pods -L app
NAME READY STATUS RESTARTS AGE APP
pod-demo 1/1 Running 0 15m nginx
[root@docker79 manifests]# kubectl get pods -l app --show-labels
NAME READY STATUS RESTARTS AGE LABELS
pod-demo 1/1 Running 0 15m app=nginx,tier=frontend
[root@docker79 manifests]# kubectl label pods pod-demo release=canary 手工打标签
pod/pod-demo labeled
[root@docker79 manifests]# kubectl get pods --show-labels
NAME READY STATUS RESTARTS AGE LABELS
pod-demo 1/1 Running 0 24m app=nginx,release=canary,tier=frontend
[root@docker79 manifests]# kubectl label pods pod-demo release=canary2 --overwrite
pod/pod-demo labeled
[root@docker79 manifests]# kubectl get pods --show-labels
NAME READY STATUS RESTARTS AGE LABELS
pod-demo 1/1 Running 0 25m app=nginx,release=canary2,tier=frontend
[root@docker79 manifests]#

Selector标签选择器
支持两类：1、等值关系的标签选择器 ； 2、集合关系的标签选择器。
等值关系： = , == , !=
集合关系： in , notin
[root@docker79 manifests]# kubectl get pods -l "release in (canary,beta,alpha)"
NAME READY STATUS RESTARTS AGE
pod-demo 1/1 Running 0 28m
[root@docker79 manifests]#

标签选择器关联其它资源（如pod控制器和service) 。使用以下两个字段进行关联：
matchLabels: 直接给定键值
matchExpressions: 基于给定的表达式来定义使用标签选择器 ,定义格式如 { key: "KEY", operator: "OPERATER", value: [ VAL1, VAL2, …]}
操作符： In , NotIn (values字段的值必须为非空列表） Exists , NotExists（values字段的值必须为空列表)

节点标签选择器
nodeSelector <map[string]string>
例：

[root@docker79 manifests]# kubectl get nodes --show-labels
NAME       STATUS    ROLES     AGE       VERSION   LABELS
docker77   Ready     <none>    2d        v1.11.2   beta.kubernetes.io/arch=amd64,beta.kubernetes.io/os=linux,kubernetes.io/hostname=docker77
docker78   Ready     <none>    2d        v1.11.2   beta.kubernetes.io/arch=amd64,beta.kubernetes.io/os=linux,kubernetes.io/hostname=docker78
docker79   Ready     master    2d        v1.11.2   beta.kubernetes.io/arch=amd64,beta.kubernetes.io/os=linux,kubernetes.io/hostname=docker79,node-role.kubernetes.io/master=
[root@docker79 manifests]#
[root@docker79 manifests]# kubectl label node docker77 diskType=ssd
node/docker77 labeled
[root@docker79 manifests]# kubectl get nodes --show-labels
NAME       STATUS    ROLES     AGE       VERSION   LABELS
docker77   Ready     <none>    2d        v1.11.2   beta.kubernetes.io/arch=amd64,beta.kubernetes.io/os=linux,diskType=ssd,kubernetes.io/hostname=docker77
docker78   Ready     <none>    2d        v1.11.2   beta.kubernetes.io/arch=amd64,beta.kubernetes.io/os=linux,kubernetes.io/hostname=docker78
docker79   Ready     master    2d        v1.11.2   beta.kubernetes.io/arch=amd64,beta.kubernetes.io/os=linux,kubernetes.io/hostname=docker79,node-role.kubernetes.io/master=
[root@docker79 manifests]#
[root@docker79 manifests]# kubectl delete -f pod-demo.yaml
pod "pod-demo" deleted
[root@docker79 manifests]# vim pod-demo.yaml
[root@docker79 manifests]# cat pod-demo.yaml
apiVersion: v1
kind: Pod
metadata:
  name: pod-demo
  namespace: default
  labels:
    app: nginx
    tier: frontend
spec:
  containers:
  - name: nginx
    image: nginx:1-alpine
    imagePullPolicy: IfNotPresent
    ports:
    - containerPort: 80
      name: http
    - name: https
      containerPort: 443
  nodeSelector:
    diskType: ssd
[root@docker79 manifests]#
[root@docker79 manifests]# kubectl apply -f pod-demo.yaml
pod/pod-demo created
[root@docker79 manifests]# kubectl get pods -o wide
NAME       READY     STATUS              RESTARTS   AGE       IP        NODE       NOMINATED NODE
pod-demo   0/1       ContainerCreating   0          17s       <none>    docker77   <none>
[root@docker79 manifests]#

annotations (资源注解)
与label不同之处在于： 它不能用于挑选资源对象，仅用于为对象提供“元数据”。
例：

[root@docker79 manifests]# kubectl delete -f pod-demo.yaml
pod "pod-demo" deleted
[root@docker79 manifests]# vim pod-demo.yaml
[root@docker79 manifests]# cat pod-demo.yaml
apiVersion: v1
kind: Pod
metadata:
  name: pod-demo
  namespace: default
  labels:
    app: nginx
    tier: frontend
  annotations:
    inspiry.cn/author: "cluster admin"
spec:
  containers:
  - name: nginx
    image: nginx:1-alpine
    imagePullPolicy: IfNotPresent
    ports:
    - containerPort: 80
      name: http
    - name: https
      containerPort: 443
  nodeSelector:
    diskType: ssd
[root@docker79 manifests]# kubectl apply -f pod-demo.yaml
pod/pod-demo created
[root@docker79 manifests]# kubectl get pods -o wide
NAME       READY     STATUS    RESTARTS   AGE       IP           NODE       NOMINATED NODE
pod-demo   1/1       Running   0          13s       10.244.2.9   docker77   <none>
[root@docker79 manifests]# kubectl describe pod pod-demo
Name:               pod-demo
Namespace:          default
Priority:           0
PriorityClassName:  <none>
Node:               docker77/192.168.20.77
Start Time:         Wed, 26 Sep 2018 16:25:44 +0800
Labels:             app=nginx
                    tier=frontend
Annotations:        inspiry.cn/author=cluster admin
   ......

三、pod生命周期
状态： Pending ， Running ，Failed， Successded ， Unknown
Pod生命周期中的重要行为：
1) 初始化container
2) container探测：liveness probe（存活探测) 和 readiness probe (就绪探测)
以上两种探测使用的探针类型有：ExeAction、TCPSocketAction、HTTPGetAction
探针探测时的常用选项如下：
failureThreshold 探测多少次宣告失败，默认3次
periodSeconds 每次间隔时长，默认10s
timeoutSeconds 每次的超时时长，默认1s
initialDelaySeconds 初始延时的时长，默认立即探测
探测结果的重启策略restartPolicy 有以下三种值：
Always: 一旦故障，立即重启
Never: 不重启
OnFailure: 只有出现 failure状态时才重启
3) 启动后勾子和中止前勾子 lifecycle
kubectl explain pods.spec.containers.lifecycle.postStart
kubectl explain pods.spec.containers.lifecycle.preStop

例1-liveness：

[root@docker79 manifests]# vim liveness-exec.yaml
[root@docker79 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/health"]
      initialDelaySeconds: 1
      periodSeconds: 3
  restartPolicy: Never
[root@docker79 manifests]# kubectl apply -f liveness-exec.yaml
pod/liveness-exec-pod created
[root@docker79 manifests]# kubectl get pods
NAME                READY     STATUS    RESTARTS   AGE
liveness-exec-pod   1/1       Running   0          6s
pod-demo            1/1       Running   0          18m
[root@docker79 manifests]# kubectl get pods
NAME                READY     STATUS    RESTARTS   AGE
liveness-exec-pod   0/1       Error     0          51s
pod-demo            1/1       Running   0          19m
[root@docker79 manifests]#

说明：container启动之后在30s之内 成功探测/tmp/health 文件存在，所以container status处于running状态；但30s之后/tmp/health文件被rm，导致探测/tmp/health文件不存在，所以container status处于Eroor 。

例2-liveness：

 [root@docker79 manifests]# vim liveness-httpsocket.yaml
[root@docker79 manifests]# cat liveness-httpsocket.yaml
apiVersion: v1
kind: Pod
metadata:
  name: liveness-httpget-pod
  namespace: default
spec:
  containers:
  - name: liveness-httpget-container
    image: nginx:1-alpine
    imagePullPolicy: IfNotPresent
    ports:
    - name: http
      containerPort: 80
    livenessProbe:
      httpGet:
        port: http
        path: /index.html
      initialDelaySeconds: 1
      periodSeconds: 3
[root@docker79 manifests]# kubectl apply -f liveness-httpsocket.yaml
pod/liveness-httpget-pod created
[root@docker79 manifests]# kubectl get pods -o wide
NAME                   READY     STATUS    RESTARTS   AGE       IP            NODE       NOMINATED NODE
liveness-httpget-pod   1/1       Running   0          8s        10.244.1.13   docker78   <none>
pod-demo               1/1       Running   0          2h        10.244.2.9    docker77   <none>
[root@docker79 manifests]#
[root@docker79 manifests]# kubectl exec -it liveness-httpget-pod -- /bin/sh
/ # ls /usr/share/nginx/html/
50x.html    index.html
/ # rm /usr/share/nginx/html/index.html -f
/ # exit
[root@docker79 manifests]# kubectl get pods -o wide
NAME                   READY     STATUS    RESTARTS   AGE       IP            NODE       NOMINATED NODE
liveness-httpget-pod   1/1       Running   1          2m        10.244.1.13   docker78   <none>
pod-demo               1/1       Running   0          2h        10.244.2.9    docker77   <none>
[root@docker79 manifests]#

说明：当httpGetAction探针探测到无法访问 /index.html 时，立即执行restartPolicy重启策略，该策略默认值always，所以可以看到 pod 的 restarts 为1.

例3-readiness：

 [root@docker79 manifests]# vim readiness-httpget.yaml
[root@docker79 manifests]# cat readiness-httpget.yaml
apiVersion: v1
kind: Pod
metadata:
  name: readiness-httpget-pod
  namespace: default
spec:
  containers:
  - name: readiness-httpget-container
    image: nginx:1-alpine
    imagePullPolicy: IfNotPresent
    ports:
    - name: http
      containerPort: 80
    readinessProbe:
      httpGet:
        port: http
        path: /index.html
      initialDelaySeconds: 1
      periodSeconds: 3
[root@docker79 manifests]# kubectl apply -f readiness-httpget.yaml
pod/readiness-httpget-pod created
[root@docker79 manifests]# kubectl get pods -o wide
NAME                    READY     STATUS    RESTARTS   AGE       IP            NODE       NOMINATED NODE
pod-demo                1/1       Running   0          3h        10.244.2.9    docker77   <none>
readiness-httpget-pod   1/1       Running   0          9s        10.244.1.14   docker78   <none>
[root@docker79 manifests]# kubectl exec -it readiness-httpget-pod -- /bin/sh
/ # rm -f /usr/share/nginx/html/index.html
/ #
[root@docker79 manifests]# kubectl get pods -o wide
NAME                    READY     STATUS    RESTARTS   AGE       IP            NODE       NOMINATED NODE
pod-demo                1/1       Running   0          3h        10.244.2.9    docker77   <none>
readiness-httpget-pod   0/1       Running   0          1m        10.244.1.14   docker78   <none>
[root@docker79 manifests]# kubectl exec -it readiness-httpget-pod -- /bin/sh
/ # echo readiness > /usr/share/nginx/html/index.html
/ # [root@docker79 manifests]#
[root@docker79 manifests]# kubectl get pods -o wide
NAME                    READY     STATUS    RESTARTS   AGE       IP            NODE       NOMINATED NODE
pod-demo                1/1       Running   0          3h        10.244.2.9    docker77   <none>
readiness-httpget-pod   1/1       Running   0          2m        10.244.1.14   docker78   <none>
[root@docker79 manifests]#

说明：就绪探测与service 调度有紧密关联，只有就绪的pod才能被调度。例3中当删除/usr/share/nginx/html/index.html之后，探针无法获取/index.html，所以pod的READY状态处于0/1状态；当再次创建/usr/share/nginx/html/index.html之后，探针有效探测到/index.html之后，pod的READY状态处于1/1状态。

例4-lifecycle：

[root@docker79 manifests]# vim lifecycle-poststart.yaml
[root@docker79 manifests]# cat lifecycle-poststart.yaml
apiVersion: v1
kind: Pod
metadata:
  name: lifecycle-poststart-pod
  namespace: default
spec:
  containers:
  - name: lifecycle-poststart-container
    image: busybox:latest
    imagePullPolicy: IfNotPresent
    lifecycle:
      postStart:
        exec:
          command: ["mkdir","-p","/var/www/inspiry"]
    command: ["/bin/sh","-c","sleep 60; /bin/httpd -f -h /var/www/inspiry"]
[root@docker79 manifests]# kubectl apply -f lifecycle-poststart.yaml
pod/lifecycle-poststart-pod created
[root@docker79 manifests]# kubectl get pods -o wide
NAME                      READY     STATUS    RESTARTS   AGE       IP            NODE       NOMINATED NODE
lifecycle-poststart-pod   1/1       Running   0          9s        10.244.1.15   docker78   <none>
[root@docker79 manifests]# kubectl exec -it lifecycle-poststart-pod -- /bin/sh
/ # ls /var/www/
inspiry
/ # netstat -tnlp
Active Internet connections (only servers)
Proto Recv-Q Send-Q Local Address           Foreign Address         State       PID/Program name
tcp        0      0 :::80                   :::*                    LISTEN      1/httpd
/ # exit
[root@docker79 manifests]#

说明：例4中使用lifecycle.postStart.exec 表示pod中container启动后执行的命令.

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