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kubernetes系列06—kubernetes资源清单定义入门

solution 2019-01-24 11:19 148 查看

本文收录在容器技术学习系列文章总目录

1、认识kubernetes资源

1.1 常用资源/对象

  •  workload工作负载型资源:pod,ReplicaSet,Deployment,StatefulSet,daemonset,job...
  •  服务器发现及均衡:Service,Lngress...
  •  配置与存储:volume,CSI  configmap,secret
  •  downwardAPI
  •  集群级资源
       namespace,node,role,clusterrole,rolebinding,clusterrolebinding
  •  元数据型资源
       HPA,podtemplate,limitrange

     

    1.2 创建资源的方法

    •  apiserver 仅接受JSON格式的资源定义;
    •  yaml格式提供配置清单,apiserver 可自动将其转为JSON格式,而后再提交;

     

    1.3 大部分(主流)资源的配置清单:有5个一级字段组成

    •  apiserver:group/version  查询当前支持哪些apiserver:$ kubectl api-versions
  •  kind:资源类别
  •  metadata:元数据
       name:名称
    •  namespace:名称空间
    •  labels:标签
    •  annotation:资源注解
    •  selfLink:每个资源的引用PATH,/api/GROUP/VERSION/namespaces/NAMESPACE/TYPE/NAME
  •  spec:期望的状态(disired state),期望资源应该用于什么特性
  •  status:当前状态(current state),本字段由kubernetes集群维护,用户不能自己定义
  •  

    1.4 使用kubectl explain查询每个资源如何配置

    (1)例如查询如何定义pod资源

    [root@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	<string>
    ... ...
    kind	<string>
    ... ...
    
    metadata	<Object>
    ... ...
    spec	<Object>
    ... ...
    status	<Object>
    ... ...

      

    (2)能一级一级进入查询;如查询定义pod 的metadata字段

    [root@master ~]# kubectl explain pod.spec
    KIND:     Pod
    VERSION:  v1
    
    RESOURCE: spec <Object>
    
    DESCRIPTION:
    ... ...
    
    FIELDS:
    ... ..
    affinity	<Object>
    ... ...
    [root@master ~]# kubectl explain pod.spec.containers
    KIND:     Pod
    VERSION:  v1
    
    RESOURCE: containers <[]Object>
    
    DESCRIPTION:
    ... ...
    FIELDS:
    args	<[]string>
    ... ...
    command	<[]string>
    ... ...

    自己定义资源时,不清楚如何定义,可以进行快速的查询

     

    1.5 示例

    (1)查询集群中的pod(上篇创建的pod)

    [root@master ~]# kubectl get pods
    NAME                          READY     STATUS    RESTARTS   AGE
    client                        1/1       Running   0          4h
    myapp-848b5b879b-9slqg        1/1       Running   0          46m
    myapp-848b5b879b-wtrjr        1/1       Running   0          46m
    myapp-848b5b879b-z2sqc        1/1       Running   0          46m

      

    (2)-o yaml输出为yaml格式,查看pod创建的操作

    [root@master ~]# kubectl get pod myapp-848b5b879b-9slqg -o yaml
    apiVersion: v1  #api版本
    kind: Pod  #资源类别
    metadata:  #元数据
    annotations:
    cni.projectcalico.org/podIP: 10.244.1.60/32
    labels:
    pod-template-hash: "4046164356"
    run: myapp
    name: myapp-848b5b879b-9slqg
    namespace: default
    ... ...
    selfLink: /api/v1/namespaces/default/pods/myapp-848b5b879b-9slqg
    spec:  #规格、规范;期望资源应该用于什么特性;期望目标状态
    ... ...
    status:  #当前状态
    ... ...

      

    1.6 演示:基于yaml格式文件,创建pod

    [root@master ~]# mkdir manifests
    [root@master ~]# cd manifests/

     

    (1)编写pod-demo.yaml文件

    创建2个容器,一个运行nginx;一个在busybox中执行sleep命令

    [root@master manifests]# vim pod-demo.yaml
    apiVersion: v1
    kind: Pod
    metadata:
    name: pod-demo
    namespace: default
    #labels: {app:myapp, tier:frontend} #映射可以写为{}形式;
    labels: #也可以在下边分级写
    app: myapp
    tier: frontend
    spec:
    containers:
    - name: myapp
    image: ikubernetes/myapp:v1
    - name: busybox
    image: busybox:latest
    #command: ["/bin/sh","-c","sleep 3600"]  #列表可以写为[]形式;
    command: #也可以在下边分级写,要加-
    - "/bin/sh"
    - "-c"
    - "sleep 3600"

      

    (2)基于pod-demo.yaml 文件创建create pod

    [root@master manifests]# kubectl create -f pod-demo.yaml
    pod/pod-demo created

      

    (3)验证

    ① 查询创建pod的信息

    [root@master manifests]# kubectl create -f pod-demo.yaml
    pod/pod-demo created[root@master manifests]# kubectl get pods -o wide
    NAME       READY     STATUS    RESTARTS   AGE       IP            NODE
    pod-demo   2/2       Running   0          1m        10.244.1.61   node1
    ---查看详细信息
    [root@master manifests]# kubectl describe pods pod-demo
    Name:               pod-demo
    Namespace:          default
    ... ...
    

    ② 访问pod中的服务

    [root@master manifests]# curl 10.244.1.61
    Hello MyApp | Version: v1 | <a href="hostname.html">Pod Name</a>
    ---查询pod产生的日志
    [root@master manifests]# kubectl logs pod-demo myapp
    192.168.130.104 - - [23/Jan/2019:05:35:35 +0000] "GET / HTTP/1.1" 200 65 "-" "curl/7.29.0" "-"

    ③ 基于yaml文件删除pod

    [root@master manifests]# kubectl delete -f pod-demo.yaml
    pod "pod-demo" deleted
    [root@master manifests]# kubectl get pods
    No resources found.

      

    2、Pod资源

    2.1 Pod资源常用选项

    •  metadata.label:标签  key=value  key:字母、数字、_、-、.
    •  value:可以为空,只能字母或数字开头及结尾,中间可使用字母、数字、_、-、.
  •  metadata.annotations:资源注解
  •  spec.containers <[]object>
       - name:容器名称
    •    image:镜像
    •    imagePullPolicy:下载镜像规则,若镜像时latest标签,默认是Always;否则默认IfNotPresen  Always总是镜像,Never不下载镜像,IfNotPresent本地有则不下载
  •  ports:从容器中公开的端口列表
       containerPort:Pod中服务的端口号
    •  hostIP:暴露绑定在主机哪个IP上
    •  hostPort:暴露在主机的端口号
    •  name:暴露这个端口的名称
  •  args:参数
  •  command:执行命令
  •  spec.nodeSelector:节点标签选择器
  •  

    2.2 演示

    (1)修改pod-demo.yaml文件

    [root@master manifests]# vim pod-demo.yaml
    apiVersion: v1
    kind: Pod
    metadata:
    name: pod-demo
    namespace: default
    #labels: {app:myapp, tier:frontend} #映射可以写为{}形式;
    labels: #也可以在下边分级写
    app: myapp
    tier: frontend
    annotations:
    along.com/created-by: "cluster admin"
    spec:
    containers:
    - name: myapp
    image: ikubernetes/myapp:v1
    ports:
    - name: http
    containerPort: 80
    - name: https
    containerPort: 443
    - name: busybox
    image: busybox:latest
    imagePullPolicy: IfNotPresent
    #command: ["/bin/sh","-c","sleep 3600"]  #列表可以写为[]形式;
    command: #也可以在下边分级写,要加-
    - "/bin/sh"
    - "-c"
    - "sleep 3600"
    nodeSelector:
    disktype: ssd

      

    (2)将node1节点打上disktype=ssd的标签

    [root@master manifests]# kubectl label node node1 disktype=ssd
    [root@master manifests]# kubectl get nodes node1 --show-labels
    NAME      STATUS    ROLES     AGE       VERSION   LABELS
    node1     Ready     <none>    140d      v1.11.2   beta.kubernetes.io/arch=amd64,beta.kubernetes.io/os=linux,disktype=ssd,kubernetes.io/hostname=node1

      

    (3)基于yaml文件创建pod

    [root@master manifests]# kubectl create -f pod-demo.yaml
    pod/pod-demo created

      

    (4)验证

    --- pod只会创建到node1节点上,因为node1的disktype=ssd标签
    [root@master manifests]# kubectl get pod -o wide
    NAME       READY     STATUS    RESTARTS   AGE       IP            NODE
    pod-demo   2/2       Running   0          11s       10.244.1.68   node1
    --- -l 指定标签,实现标签过滤
    [root@master manifests]# kubectl get pods --show-labels -l app
    NAME       READY     STATUS    RESTARTS   AGE       LABELS
    pod-demo   2/2       Running   0          30s       app=myapp,tier=frontend

      

    3、Pod健康检测

    3.1 pod健康检测介绍

    •  pod健康检测分为存活性探测、 就绪型探测;这在生产环境几乎是必须配置的;
    •  如果没有就绪型探测;pod一启动就会被分配用户流量;若pod中的服务像tomcat等,需要时间启动;就会导致有一定时间,用户访问不到服务;
    •  如果没有存活性探测:pod中服务一旦失败,没有检测,不会将容器重启关闭;也会导致用户访问服务失败。

     

    3.2 pod健康检测选项

    (1)在spec字段下、containers字段配置,可使用explain查看详细用法

    $ kubectl explain pod.spec.containers.

    •  livenessProbe 存活性探测  exec:指定检测的命令
    •  failureThreshold:连续失败次数被认为失败,默认为3,最小值为1
    •  httpGet:指定要执行的http请求
    •  initialDelaySeconds:在容器启动多少秒后再检测
    •  periodSeconds:每隔多少秒探测一次;默认为10秒。最低限度值是1
    •  successThreshold:连续成功次数认为服务正常
    •  tcpSocket:定涉及TCP端口的操作
    •  timeoutSeconds:探测超时的秒数,默认为1秒
  •  readinessProbe 就绪型探测(和livenessProbe 存活性探测选项一样)
  •  

    (2)pod中容器挂了,是否重启pod

    $ kubectl explain pod.spec.restartPolicy.   

    • Always:总是重启(默认)
    • OnFailure:只有容器状态为错误时,才重启
    • Never:绝不重启

     

    3.3 演示:exec方式实现存活性探测

    (1)编写yaml文件

    当探测到/tmp/healthy文件不存在时,认为服务故障;

    容器在30秒后执行删除/tmp/healthy文件

    [root@master manifests]# vim 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: 1  #在容器启动后1秒开始检测
    periodSeconds: 3  #每隔3秒探测一次
    restartPolicy: Always  #总是重启pod

      

    (2)创建运行pod

    [root@master manifests]# kubectl create -f liveness-exec.yaml
    pod/liveness-exec-pod created
    [root@master manifests]# kubectl get pods
    NAME                READY     STATUS        RESTARTS   AGE
    liveness-exec-pod   1/1       Running       0          6s

      

    (3)等30s,容器就会检测失败,重启pod;使用describe可以查看详细信息

    [root@master manifests]# kubectl describe pods liveness-exec-pod
    ... ...
    State:          Running
    Started:      Wed, 23 Jan 2019 16:58:09 +0800
    Last State:     Terminated  #上次状态为终止
    Reason:       Error
    Exit Code:    137
    Started:      Wed, 23 Jan 2019 16:57:01 +0800
    Finished:     Wed, 23 Jan 2019 16:58:09 +0800
    Ready:          True
    Restart Count:  1  #重启次数1次
    Liveness:       exec [test -e /tmp/healthy] delay=1s timeout=1s period=3s #success=1 #failure=3
    ... ...

      

    3.4 演示:httpget方式实现存活性探测

    (1)编写yaml文件,创建并运行pod

    当探测不到容器内80端口,和提供80端口的/index.html文件时,认为服务故障;

    [root@master manifests]# vim liveness-httpget.yaml
    apiVersion: v1
    kind: Pod
    metadata:
    name: liveness-httpget-pod
    namespace: default
    spec:
    containers:
    - name: liveness-exec-container
    image: ikubernetes/myapp:v1
    ports:
    - name: http
    containerPort: 80
    livenessProbe:
    httpget:
    port: http
    path: /index.html
    initialDelaySeconds: 1
    periodSeconds: 3
    restartPolicy: Always
    [root@master manifests]# kubectl create -f liveness-httpget.yaml
    pod/liveness-httpget-pod created

      

    (2)手动连入容器,删除index.html文件

    [root@master manifests]# kubectl exec -it liveness-httpget-pod -- /bin/sh
    / # rm -f /usr/share/nginx/html/index.html

      

    (3)容器会检测失败,重启pod;使用describe可以查看详细信息

    [root@master manifests]# kubectl describe pods liveness-httpget-pod
    ... ...
    Port:           80/TCP
    Host Port:      0/TCP
    State:          Running
    Started:      Wed, 23 Jan 2019 17:10:03 +0800
    Last State:     Terminated  #上次状态为终止
    Reason:       Completed
    Exit Code:    0
    Started:      Wed, 23 Jan 2019 17:08:22 +0800
    Finished:     Wed, 23 Jan 2019 17:10:03 +0800
    Ready:          True
    Restart Count:  1  #重启次数1次
    Liveness:       http-get http://:http/index.html delay=1s timeout=1s period=3s #success=1 #failure=3
    ... ...

      

    3.5 演示:exec方式实现就绪性探测

    (1)编写yaml文件,创建启动容器

    当探测到/tmp/healthy文件不存在时,就认为服务就绪不成功;pod启动失败;

    [root@master manifests]# vim readiness-exec.yaml
    apiVersion: v1
    kind: Pod
    metadata:
    name: readiness-exec-pod
    namespace: default
    spec:
    containers:
    - name: readiness-exec-container
    image: busybox:latest
    imagePullPolicy: IfNotPresent
    #command: ["/bin/sh","-c","touch /tmp/healthy; sleep 30; rm -f /tmp/healthy; sleep 3600"]
    command: ["sleep 3600"]
    readinessProbe:
    exec:
    command: ["test","-e","/tmp/healthy"]
    periodSeconds: 3
    restartPolicy: Always
    [root@master manifests]# kubectl create -f readiness-exec.yaml
    pod/readiness-exec-pod created

      

    (2)查看,pod启动就绪失败

    [root@master ~]# kubectl get pods
    NAME                 READY     STATUS              RESTARTS   AGE
    readiness-exec-pod   0/1       RunContainerError   1          12s

      

    4、Pod启动前/后钩子

    4.1 介绍

    •  pod在启动前后都可以设置钩子hook;在spec.containers.lifecycle字段下设置;
    •  postStart:创建容器后立即调用PostStart操作;如果失败,根据重启策略终止;
    •  preStop:在容器终止之前立即调用PreStop操作,该容器在处理程序完成后终止

     

    4.2 语法

    $ kubectl explain pod.spec.containers.lifecycle

    •  postStart  exec:指定了要采取的命令;
    •  httpGet:指定要执行的http请求;
    •  tcpSocket:指定涉及TCP端口的操作
  •  preStop (和postStart命令一样)
  •  

    4.3 演示:使用exec设置pod启动前钩子

    (1)编写yaml文件,创建启动容器

    启动容器前,先创建准备一个httpd服务的主页面文件/tmp/index.html

    [root@master manifests]# vim poststart-pod.yaml
    apiVersion: v1
    kind: Pod
    metadata:
    name: poststart-pod
    namespace: default
    spec:
    containers:
    - name:  poststart-container
    image: busybox:latest
    imagePullPolicy: IfNotPresent
    lifecycle:
    postStart:
    exec:
    command: ['/bin/sh','-c','echo hello > /tmp/index.html']
    command: ['/bin/sh','-c','/bin/httpd -f -h /tmp']
    [root@master manifests]# kubectl create -f poststart-pod.yaml
    pod/poststart-pod created

      

    (2)验证,访问服务

    [root@master ~]# kubectl get pods -o wide
    NAME            READY     STATUS    RESTARTS   AGE       IP            NODE
    poststart-pod   1/1       Running   0          26s       10.244.2.69   node2
    [root@master ~]# curl 10.244.2.69
    hello

      

     

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