K8s暴露服务-服务发现(三种常用方式)

一、基本概念

1、Kubernetes 暴露服务的方式:

NodePort:后期维护困难,不支持虚拟路径

LoadBlancer:需要云厂商支持,有局限性

ClusterIP:只能在集群内部访问

Ingress:灵活,无依赖

前三种方式都是在service的维度提供的,service的作用体现在两个方面,对集群内部它不断跟踪pod变化,更新endpoint中对应的pod的对象,提供IP不断变化的pod的服务发现机制;对集群外部,它类似负载均衡器,可以在集群内外对pod进行访问。但是单独使用service暴露服务的方式,在实际生产环境中不太适应。

而ingress相当于service的service,可以将外部请求通过不同规则的筛选后转发到不同的service

2、ingress与ingress-controller

ingress是k8s中的一个api对象,一般用yaml配置。作用是定义请求转发的规则,可以理解为配置模板或者配置文件。

ingress-controller是具体实现反向代理及负载均衡的程序,通过对ingress中定义的规则进行解析,根据其规则来实现转发。

ingress-controller并不是k8s自带的组件,实际上它只是一个统称,用户可以选择不同的ingress-controller来实现功能。其中由k8s官方维护的是nginx-ingress。

以下为ingress-controller.yaml文件根据本地k8s服务修改后的部署文件,主要修改内容:

1.修改国外镜像源为国内阿里云镜像源

2.添加hostNetwork网络模式

3.添加nodeName参数,我的值为 k8s-master ,此处需根据自己本地管理节点的hostname调整
apiVersion: v1
kind: Namespace
metadata:
  labels:
    app.kubernetes.io/instance: ingress-nginx
    app.kubernetes.io/name: ingress-nginx
  name: ingress-nginx
---
apiVersion: v1
automountServiceAccountToken: true
kind: ServiceAccount
metadata:
  labels:
    app.kubernetes.io/component: controller
    app.kubernetes.io/instance: ingress-nginx
    app.kubernetes.io/name: ingress-nginx
    app.kubernetes.io/part-of: ingress-nginx
    app.kubernetes.io/version: 1.3.0
  name: ingress-nginx
  namespace: ingress-nginx
---
apiVersion: v1
kind: ServiceAccount
metadata:
  labels:
    app.kubernetes.io/component: admission-webhook
    app.kubernetes.io/instance: ingress-nginx
    app.kubernetes.io/name: ingress-nginx
    app.kubernetes.io/part-of: ingress-nginx
    app.kubernetes.io/version: 1.3.0
  name: ingress-nginx-admission
  namespace: ingress-nginx
---
apiVersion: rbac.authorization.k8s.io/v1
kind: Role
metadata:
  labels:
    app.kubernetes.io/component: controller
    app.kubernetes.io/instance: ingress-nginx
    app.kubernetes.io/name: ingress-nginx
    app.kubernetes.io/part-of: ingress-nginx
    app.kubernetes.io/version: 1.3.0
  name: ingress-nginx
  namespace: ingress-nginx
rules:
- apiGroups:
  - ""
  resources:
  - namespaces
  verbs:
  - get
- apiGroups:
  - ""
  resources:
  - configmaps
  - pods
  - secrets
  - endpoints
  verbs:
  - get
  - list
  - watch
- apiGroups:
  - ""
  resources:
  - services
  verbs:
  - get
  - list
  - watch
- apiGroups:
  - networking.k8s.io
  resources:
  - ingresses
  verbs:
  - get
  - list
  - watch
- apiGroups:
  - networking.k8s.io
  resources:
  - ingresses/status
  verbs:
  - update
- apiGroups:
  - networking.k8s.io
  resources:
  - ingressclasses
  verbs:
  - get
  - list
  - watch
- apiGroups:
  - ""
  resourceNames:
  - ingress-controller-leader
  resources:
  - configmaps
  verbs:
  - get
  - update
- apiGroups:
  - ""
  resources:
  - configmaps
  verbs:
  - create
- apiGroups:
  - coordination.k8s.io
  resourceNames:
  - ingress-controller-leader
  resources:
  - leases
  verbs:
  - get
  - update
- apiGroups:
  - coordination.k8s.io
  resources:
  - leases
  verbs:
  - create
- apiGroups:
  - ""
  resources:
  - events
  verbs:
  - create
  - patch
---
apiVersion: rbac.authorization.k8s.io/v1
kind: Role
metadata:
  labels:
    app.kubernetes.io/component: admission-webhook
    app.kubernetes.io/instance: ingress-nginx
    app.kubernetes.io/name: ingress-nginx
    app.kubernetes.io/part-of: ingress-nginx
    app.kubernetes.io/version: 1.3.0
  name: ingress-nginx-admission
  namespace: ingress-nginx
rules:
- apiGroups:
  - ""
  resources:
  - secrets
  verbs:
  - get
  - create
---
apiVersion: rbac.authorization.k8s.io/v1
kind: ClusterRole
metadata:
  labels:
    app.kubernetes.io/instance: ingress-nginx
    app.kubernetes.io/name: ingress-nginx
    app.kubernetes.io/part-of: ingress-nginx
    app.kubernetes.io/version: 1.3.0
  name: ingress-nginx
rules:
- apiGroups:
  - ""
  resources:
  - configmaps
  - endpoints
  - nodes
  - pods
  - secrets
  - namespaces
  verbs:
  - list
  - watch
- apiGroups:
  - coordination.k8s.io
  resources:
  - leases
  verbs:
  - list
  - watch
- apiGroups:
  - ""
  resources:
  - nodes
  verbs:
  - get
- apiGroups:
  - ""
  resources:
  - services
  verbs:
  - get
  - list
  - watch
- apiGroups:
  - networking.k8s.io
  resources:
  - ingresses
  verbs:
  - get
  - list
  - watch
- apiGroups:
  - ""
  resources:
  - events
  verbs:
  - create
  - patch
- apiGroups:
  - networking.k8s.io
  resources:
  - ingresses/status
  verbs:
  - update
- apiGroups:
  - networking.k8s.io
  resources:
  - ingressclasses
  verbs:
  - get
  - list
  - watch
---
apiVersion: rbac.authorization.k8s.io/v1
kind: ClusterRole
metadata:
  labels:
    app.kubernetes.io/component: admission-webhook
    app.kubernetes.io/instance: ingress-nginx
    app.kubernetes.io/name: ingress-nginx
    app.kubernetes.io/part-of: ingress-nginx
    app.kubernetes.io/version: 1.3.0
  name: ingress-nginx-admission
rules:
- apiGroups:
  - admissionregistration.k8s.io
  resources:
  - validatingwebhookconfigurations
  verbs:
  - get
  - update
---
apiVersion: rbac.authorization.k8s.io/v1
kind: RoleBinding
metadata:
  labels:
    app.kubernetes.io/component: controller
    app.kubernetes.io/instance: ingress-nginx
    app.kubernetes.io/name: ingress-nginx
    app.kubernetes.io/part-of: ingress-nginx
    app.kubernetes.io/version: 1.3.0
  name: ingress-nginx
  namespace: ingress-nginx
roleRef:
  apiGroup: rbac.authorization.k8s.io
  kind: Role
  name: ingress-nginx
subjects:
- kind: ServiceAccount
  name: ingress-nginx
  namespace: ingress-nginx
---
apiVersion: rbac.authorization.k8s.io/v1
kind: RoleBinding
metadata:
  labels:
    app.kubernetes.io/component: admission-webhook
    app.kubernetes.io/instance: ingress-nginx
    app.kubernetes.io/name: ingress-nginx
    app.kubernetes.io/part-of: ingress-nginx
    app.kubernetes.io/version: 1.3.0
  name: ingress-nginx-admission
  namespace: ingress-nginx
roleRef:
  apiGroup: rbac.authorization.k8s.io
  kind: Role
  name: ingress-nginx-admission
subjects:
- kind: ServiceAccount
  name: ingress-nginx-admission
  namespace: ingress-nginx
---
apiVersion: rbac.authorization.k8s.io/v1
kind: ClusterRoleBinding
metadata:
  labels:
    app.kubernetes.io/instance: ingress-nginx
    app.kubernetes.io/name: ingress-nginx
    app.kubernetes.io/part-of: ingress-nginx
    app.kubernetes.io/version: 1.3.0
  name: ingress-nginx
roleRef:
  apiGroup: rbac.authorization.k8s.io
  kind: ClusterRole
  name: ingress-nginx
subjects:
- kind: ServiceAccount
  name: ingress-nginx
  namespace: ingress-nginx
---
apiVersion: rbac.authorization.k8s.io/v1
kind: ClusterRoleBinding
metadata:
  labels:
    app.kubernetes.io/component: admission-webhook
    app.kubernetes.io/instance: ingress-nginx
    app.kubernetes.io/name: ingress-nginx
    app.kubernetes.io/part-of: ingress-nginx
    app.kubernetes.io/version: 1.3.0
  name: ingress-nginx-admission
roleRef:
  apiGroup: rbac.authorization.k8s.io
  kind: ClusterRole
  name: ingress-nginx-admission
subjects:
- kind: ServiceAccount
  name: ingress-nginx-admission
  namespace: ingress-nginx
---
apiVersion: v1
data:
  allow-snippet-annotations: "true"
kind: ConfigMap
metadata:
  labels:
    app.kubernetes.io/component: controller
    app.kubernetes.io/instance: ingress-nginx
    app.kubernetes.io/name: ingress-nginx
    app.kubernetes.io/part-of: ingress-nginx
    app.kubernetes.io/version: 1.3.0
  name: ingress-nginx-controller
  namespace: ingress-nginx
---
apiVersion: v1
kind: Service
metadata:
  labels:
    app.kubernetes.io/component: controller
    app.kubernetes.io/instance: ingress-nginx
    app.kubernetes.io/name: ingress-nginx
    app.kubernetes.io/part-of: ingress-nginx
    app.kubernetes.io/version: 1.3.0
  name: ingress-nginx-controller
  namespace: ingress-nginx
spec:
  externalTrafficPolicy: Local
  ports:
  - appProtocol: http
    name: http
    port: 80
    protocol: TCP
    targetPort: http
  - appProtocol: https
    name: https
    port: 443
    protocol: TCP
    targetPort: https
  selector:
    app.kubernetes.io/component: controller
    app.kubernetes.io/instance: ingress-nginx
    app.kubernetes.io/name: ingress-nginx
  type: NodePort
---
apiVersion: v1
kind: Service
metadata:
  labels:
    app.kubernetes.io/component: controller
    app.kubernetes.io/instance: ingress-nginx
    app.kubernetes.io/name: ingress-nginx
    app.kubernetes.io/part-of: ingress-nginx
    app.kubernetes.io/version: 1.3.0
  name: ingress-nginx-controller-admission
  namespace: ingress-nginx
spec:
  ports:
  - appProtocol: https
    name: https-webhook
    port: 443
    targetPort: webhook
  selector:
    app.kubernetes.io/component: controller
    app.kubernetes.io/instance: ingress-nginx
    app.kubernetes.io/name: ingress-nginx
  type: ClusterIP
---
apiVersion: apps/v1
kind: Deployment
metadata:
  labels:
    app.kubernetes.io/component: controller
    app.kubernetes.io/instance: ingress-nginx
    app.kubernetes.io/name: ingress-nginx
    app.kubernetes.io/part-of: ingress-nginx
    app.kubernetes.io/version: 1.3.0
  name: ingress-nginx-controller
  namespace: ingress-nginx
spec:
  minReadySeconds: 0
  revisionHistoryLimit: 10
  selector:
    matchLabels:
      app.kubernetes.io/component: controller
      app.kubernetes.io/instance: ingress-nginx
      app.kubernetes.io/name: ingress-nginx
  template:
    metadata:
      labels:
        app.kubernetes.io/component: controller
        app.kubernetes.io/instance: ingress-nginx
        app.kubernetes.io/name: ingress-nginx
    spec:
      hostNetwork: true    #官方文件不包含该配置,本地起服务建议采用host网络
      nodeName: k8s-master #需调整为自己机器的部署节点名称
      containers:
      - args:
        - /nginx-ingress-controller
        - --publish-service=$(POD_NAMESPACE)/ingress-nginx-controller
        - --election-id=ingress-controller-leader
        - --controller-class=k8s.io/ingress-nginx
        - --ingress-class=nginx
        - --configmap=$(POD_NAMESPACE)/ingress-nginx-controller
        - --validating-webhook=:8443
        - --validating-webhook-certificate=/usr/local/certificates/cert
        - --validating-webhook-key=/usr/local/certificates/key
        env:
        - name: POD_NAME
          valueFrom:
            fieldRef:
              fieldPath: metadata.name
        - name: POD_NAMESPACE
          valueFrom:
            fieldRef:
              fieldPath: metadata.namespace
        - name: LD_PRELOAD
          value: /usr/local/lib/libmimalloc.so
        image: registry.cn-hangzhou.aliyuncs.com/google_containers/nginx-ingress-controller:v1.3.0
        imagePullPolicy: IfNotPresent
        lifecycle:
          preStop:
            exec:
              command:
              - /wait-shutdown
        livenessProbe:
          failureThreshold: 5
          httpGet:
            path: /healthz
            port: 10254
            scheme: HTTP
          initialDelaySeconds: 10
          periodSeconds: 10
          successThreshold: 1
          timeoutSeconds: 1
        name: controller
        ports:
        - containerPort: 80
          name: http
          protocol: TCP
        - containerPort: 443
          name: https
          protocol: TCP
        - containerPort: 8443
          name: webhook
          protocol: TCP
        readinessProbe:
          failureThreshold: 3
          httpGet:
            path: /healthz
            port: 10254
            scheme: HTTP
          initialDelaySeconds: 10
          periodSeconds: 10
          successThreshold: 1
          timeoutSeconds: 1
        resources:
          requests:
            cpu: 100m
            memory: 90Mi
        securityContext:
          allowPrivilegeEscalation: true
          capabilities:
            add:
            - NET_BIND_SERVICE
            drop:
            - ALL
          runAsUser: 101
        volumeMounts:
        - mountPath: /usr/local/certificates/
          name: webhook-cert
          readOnly: true
      dnsPolicy: ClusterFirst
      nodeSelector:
        kubernetes.io/os: linux
      serviceAccountName: ingress-nginx
      terminationGracePeriodSeconds: 300
      volumes:
      - name: webhook-cert
        secret:
          secretName: ingress-nginx-admission
---
apiVersion: batch/v1
kind: Job
metadata:
  labels:
    app.kubernetes.io/component: admission-webhook
    app.kubernetes.io/instance: ingress-nginx
    app.kubernetes.io/name: ingress-nginx
    app.kubernetes.io/part-of: ingress-nginx
    app.kubernetes.io/version: 1.3.0
  name: ingress-nginx-admission-create
  namespace: ingress-nginx
spec:
  template:
    metadata:
      labels:
        app.kubernetes.io/component: admission-webhook
        app.kubernetes.io/instance: ingress-nginx
        app.kubernetes.io/name: ingress-nginx
        app.kubernetes.io/part-of: ingress-nginx
        app.kubernetes.io/version: 1.3.0
      name: ingress-nginx-admission-create
    spec:
      containers:
      - args:
        - create
        - --host=ingress-nginx-controller-admission,ingress-nginx-controller-admission.$(POD_NAMESPACE).svc
        - --namespace=$(POD_NAMESPACE)
        - --secret-name=ingress-nginx-admission
        env:
        - name: POD_NAMESPACE
          valueFrom:
            fieldRef:
              fieldPath: metadata.namespace
        image: registry.cn-hangzhou.aliyuncs.com/google_containers/kube-webhook-certgen:v1.1.1
        imagePullPolicy: IfNotPresent
        name: create
        securityContext:
          allowPrivilegeEscalation: false
      nodeSelector:
        kubernetes.io/os: linux
      restartPolicy: OnFailure
      securityContext:
        fsGroup: 2000
        runAsNonRoot: true
        runAsUser: 2000
      serviceAccountName: ingress-nginx-admission
---
apiVersion: batch/v1
kind: Job
metadata:
  labels:
    app.kubernetes.io/component: admission-webhook
    app.kubernetes.io/instance: ingress-nginx
    app.kubernetes.io/name: ingress-nginx
    app.kubernetes.io/part-of: ingress-nginx
    app.kubernetes.io/version: 1.3.0
  name: ingress-nginx-admission-patch
  namespace: ingress-nginx
spec:
  template:
    metadata:
      labels:
        app.kubernetes.io/component: admission-webhook
        app.kubernetes.io/instance: ingress-nginx
        app.kubernetes.io/name: ingress-nginx
        app.kubernetes.io/part-of: ingress-nginx
        app.kubernetes.io/version: 1.3.0
      name: ingress-nginx-admission-patch
    spec:
      containers:
      - args:
        - patch
        - --webhook-name=ingress-nginx-admission
        - --namespace=$(POD_NAMESPACE)
        - --patch-mutating=false
        - --secret-name=ingress-nginx-admission
        - --patch-failure-policy=Fail
        env:
        - name: POD_NAMESPACE
          valueFrom:
            fieldRef:
              fieldPath: metadata.namespace
        image: registry.cn-hangzhou.aliyuncs.com/google_containers/kube-webhook-certgen:v1.1.1
        imagePullPolicy: IfNotPresent
        name: patch
        securityContext:
          allowPrivilegeEscalation: false
      nodeSelector:
        kubernetes.io/os: linux
      restartPolicy: OnFailure
      securityContext:
        fsGroup: 2000
        runAsNonRoot: true
        runAsUser: 2000
      serviceAccountName: ingress-nginx-admission
---
apiVersion: networking.k8s.io/v1
kind: IngressClass
metadata:
  labels:
    app.kubernetes.io/component: controller
    app.kubernetes.io/instance: ingress-nginx
    app.kubernetes.io/name: ingress-nginx
    app.kubernetes.io/part-of: ingress-nginx
    app.kubernetes.io/version: 1.3.0
  name: nginx
spec:
  controller: k8s.io/ingress-nginx
---
apiVersion: admissionregistration.k8s.io/v1
kind: ValidatingWebhookConfiguration
metadata:
  labels:
    app.kubernetes.io/component: admission-webhook
    app.kubernetes.io/instance: ingress-nginx
    app.kubernetes.io/name: ingress-nginx
    app.kubernetes.io/part-of: ingress-nginx
    app.kubernetes.io/version: 1.3.0
  name: ingress-nginx-admission
webhooks:
- admissionReviewVersions:
  - v1
  clientConfig:
    service:
      name: ingress-nginx-controller-admission
      namespace: ingress-nginx
      path: /networking/v1/ingresses
  failurePolicy: Fail
  matchPolicy: Equivalent
  name: validate.nginx.ingress.kubernetes.io
  rules:
  - apiGroups:
    - networking.k8s.io
    apiVersions:
    - v1
    operations:
    - CREATE
    - UPDATE
    resources:
    - ingresses
  sideEffects: None

二、配置方式

1、Deployment+LoadBalancer模式的Service

如果要把ingress部署在公有云,那用这种方式比较合适。用Deployment部署ingress-controller,创建一个type为LoadBalancer的service关联这组pod。大部分公有云,都会为LoadBalancer的service自动创建一个负载均衡器,通常还绑定了公网地址。只要把域名解析指向该地址,就实现了集群服务的对外暴露

2、Deployment+NodePort模式的Service

同样用deployment模式部署ingress-controller,并创建对应的服务,但是type为NodePort。这样,ingress就会暴露在集群节点ip的特定端口上。由于nodeport暴露的端口是随机端口,一般会在前再搭建一套负载均衡器来转发请求。该方式一般用于宿主机是相对固定的环境ip地址不变的场景。

NodePort方式暴露ingress虽然简单方便,但是NodePort多了一层NAT,在请求量级很大时可能对性能会有一定影响

3、DaemonSet+HostNetwork+nodeSelector

用DaemonSet结合nodeselector来部署ingress-controller到特定的node上(也可结合affinity亲和性部署到多个节点),然后使用HostNetwork直接把该pod与宿主机node的网络打通,直接使用宿主机的80/433端口就能访问服务。这时,ingress-controller所在的node机器就很类似传统架构的边缘节点,比如机房入口的nginx服务器。该方式整个请求链路最简单,性能相对NodePort模式更好。缺点是由于直接利用宿主机节点的网络和端口,一个node只能部署一个ingress-controller pod。比较适合大并发的生产环境使用。

三、RBAC的相关说明介绍

1、基本概念

RBAC(Role-Based Access Control,基于角色的访问控制)在k8s v1.5中引入,在v1.6版本时升级为Beta版本,并成为kubeadm安装方式下的默认选项,相对于其他访问控制方式,新的RBAC具有如下优势:

对集群中的资源和非资源权限均有完整的覆盖

整个RBAC完全由几个API对象完成,同其他API对象一样,可以用kubectl或API进行操作

可以在运行时进行调整,无需重启API Server

要使用RBAC授权模式,需要在API Server的启动参数中加上--authorization-mode=RBAC

2、RBAC的API资源对象说明

参数说明:

apiGroup:支持的API组列表,例如:APIVersion: batch/v1、APIVersion: extensions:v1、apiVersion:apps/v1等

resources:支持的资源对象列表,例如:pods、deployments、jobs等

verbs:对资源对象的操作方法列表,例如:get、watch、list、delete、replace、patch等

(1)角色(Role):

一个角色就是一组权限的集合,这里的权限都是许可形式的,不存在拒绝的规则。在一个命名空间中,可以用角色来定义一个角色,如果是集群级别的,就需要使用ClusterRole了。角色只能对命名空间内的资源进行授权

(2)集群角色(ClusterRole):

集群角色除了具有和角色一致的命名空间内资源的管理能力,因其集群级别的范围,还可以用于以下特殊元素的授权。

集群范围的资源,例如Node

非资源型的路径,例如/healthz

包含全部命名空间的资源,例如pods

(3)角色绑定(RoleBinding)和集群角色绑定(ClusterRoleBinding):

角色绑定或集群角色绑定用来把一个角色绑定到一个目标上,绑定目标可以是User、Group或者Service Account。使用RoleBinding为某个命名空间授权,ClusterRoleBinding为集群范围内授权。

RoleBinding可以引用Role进行授权

RoleBinding也可以引用ClusterRole,对属于同一命名空间内ClusterRole定义的资源主体进行授权。一种常见的做法是集群管理员为集群范围预先定义好一组角色(ClusterRole),然后在多个命名空间中重复使用这些ClusterRole。

集群角色绑定中的角色只能是集群角色,用于进行集群级别或者对所有命名空间都生效的授权。

你可能感兴趣的:(kubernetes,运维,docker,服务发现)