1，如何访问K8S中的服务：

   

k8s的ingress 请求到service 负载不均衡 k8s配置ingress_nginx

  1，Ingress介绍

       Kubernetes 暴露服务的方式目前只有三种：LoadBlancer Service、NodePort Service、Ingress；前两种估计都应该很熟悉，下面详细的了解下这个 Ingress

       Ingress由两部分组成：Ingress Controller 和 Ingress 服务。

       Ingress Contronler 通过与 Kubernetes API 交互，动态的去感知集群中 Ingress 规则变化，然后读取它，按照自定义的规则，规则就是写明了哪个域名对应哪个service，生成一段 Nginx 配置，再写到 Nginx-ingress-control的 Pod 里，这个 Ingress Contronler 的pod里面运行着一个nginx服务，控制器会把生成的nginx配置写入/etc/nginx.conf文件中，然后 reload 一下 使用配置生效。以此来达到域名分配置及动态更新的问题。

      看个简单的图方便理解：

              

k8s的ingress 请求到service 负载不均衡 k8s配置ingress_后端_02

   ingress控制器有两种：nginx和haproxy 这里是以nginx为讲解。

   

   2，部署一个Nginx Ingress

      ingress的部署文件在github Ingress 仓库找到. 针对官方配置我们单独添加了 nodeselector 指定，绑定LB地址 以方便DNS 做解析。

     主要用到的文件：



$ ls default-backend.yaml  jenkins-ingress.yml  nginx-ingress-controller-rbac.yml  nginx-ingress-controller.yaml - - -  default-backend.yaml：这是官方要求必须要给的默认后端，提供404页面的。它还提供了一个http检测功能，检测nginx-ingress-controll健康状态的，通过每隔一定时间访问nginx-ingress-controll的/healthz页面，如是没有响应就 返回404之类的错误码。 nginx-ingress-controller-rbac.yml:这ingress的RBAC授权文件 nginx-ingress-controller.yaml：这是控制器的部署文件。 jenkins-ingress.yml：这是Ingress服务文件，这个可以是任意web程序，里面配置域名与service的对应关系，Ingress称之为规则。



   第一个是要部署RBAC文件：


cat nginx-ingress-controller-rbac.yml
#apiVersion: v1
#kind: Namespace
#metadata:  #这里是创建一个namespace，因为此namespace早有了就不用再创建了
#  name: kube-system
---
apiVersion: v1
kind: ServiceAccount    
metadata:
  name: nginx-ingress-serviceaccount #创建一个serveerAcount
  namespace: kube-system
---
apiVersion: rbac.authorization.k8s.io/v1beta1
kind: ClusterRole
metadata:
  name: nginx-ingress-clusterrole   #这个ServiceAcount所绑定的集群角色
rules:
  - apiGroups:
      - "" 
    resources:    #此集群角色的权限，它能操作的API资源 
      - configmaps
      - endpoints
      - nodes
      - pods
      - secrets
    verbs:
      - list
      - watch
  - apiGroups:
      - ""
    resources:
      - nodes
    verbs:
      - get
  - apiGroups:
      - ""
    resources:
      - services
    verbs:
      - get
      - list
      - watch
  - apiGroups:
      - "extensions"
    resources:
      - ingresses
    verbs:
      - get
      - list
      - watch
  - apiGroups:
      - ""
    resources:
        - events
    verbs:
        - create
        - patch
  - apiGroups:
      - "extensions"
    resources:
      - ingresses/status
    verbs:
      - update
---
apiVersion: rbac.authorization.k8s.io/v1beta1
kind: Role
metadata:         
  name: nginx-ingress-role  #这是一个角色，而非集群角色 
  namespace: kube-system
rules:  #角色的权限 
  - apiGroups:
      - ""
    resources:
      - configmaps
      - pods
      - secrets
      - namespaces
    verbs:
      - get
  - apiGroups:
      - ""
    resources:
      - configmaps
    resourceNames:
      # Defaults to "<election-id>-<ingress-class>"
      # Here: "<ingress-controller-leader>-<nginx>"
      # This has to be adapted if you change either parameter
      # when launching the nginx-ingress-controller.
      - "ingress-controller-leader-nginx"
    verbs:
      - get
      - update
  - apiGroups:
      - ""
    resources:
      - configmaps
    verbs:
      - create
  - apiGroups:
      - ""
    resources:
      - endpoints
    verbs:
      - get
      - create
      - update
---
apiVersion: rbac.authorization.k8s.io/v1beta1
kind: RoleBinding       #角色绑定
metadata:
  name: nginx-ingress-role-nisa-binding
  namespace: kube-system
roleRef:
  apiGroup: rbac.authorization.k8s.io
  kind: Role
  name: nginx-ingress-role
subjects:
  - kind: ServiceAccount
    name: nginx-ingress-serviceaccount #绑定在这个用户 
    namespace: kube-system
---
apiVersion: rbac.authorization.k8s.io/v1beta1
kind: ClusterRoleBinding      #集群绑定
metadata:
  name: nginx-ingress-clusterrole-nisa-binding
roleRef:
  apiGroup: rbac.authorization.k8s.io
  kind: ClusterRole
  name: nginx-ingress-clusterrole
subjects:
  - kind: ServiceAccount
    name: nginx-ingress-serviceaccount   #集群绑定到这个serviceacount
    namespace: kube-system   #集群角色是可以跨namespace，但是这里只指明给这个namespce来使用



 创建：


$ kubectl create -f nginx-ingress-controller-rbac.yml 
serviceaccount "nginx-ingress-serviceaccount" created
clusterrole "nginx-ingress-clusterrole" created
role "nginx-ingress-role" created
rolebinding "nginx-ingress-role-nisa-binding" created
clusterrolebinding "nginx-ingress-clusterrole-nisa-binding" created



 RBAC创建完后，就创建default backend服务：


$ cat default-backend.yaml
apiVersion: extensions/v1beta1
kind: Deployment
metadata:
  name: default-http-backend
  labels:
    k8s-app: default-http-backend
  namespace: kube-system
spec:
  replicas: 1
  template:
    metadata:
      labels:
        k8s-app: default-http-backend
    spec:
      terminationGracePeriodSeconds: 60
      containers:
      - name: default-http-backend
        # Any image is permissable as long as:
        # 1. It serves a 404 page at /
        # 2. It serves 200 on a /healthz endpoint
        image: gcr.io/google_containers/defaultbackend:1.0
        livenessProbe:
          httpGet:
            path: /healthz   #这个URI是 nginx-ingress-controller中nginx里配置好的localtion 
            port: 8080
            scheme: HTTP
          initialDelaySeconds: 30   #30s检测一次/healthz
          timeoutSeconds: 5
        ports:
        - containerPort: 8080
        resources:
          limits:
            cpu: 10m
            memory: 20Mi
          requests:
            cpu: 10m
            memory: 20Mi
      nodeSelector:            #指定调度到些Node, 以便后面DNS解析
        kubernetes.io/hostname: 10.3.1.17    
---
apiVersion: v1
kind: Service     #为default backend 创建一个service
metadata:
  name: default-http-backend
  namespace: kube-system
  labels:
    k8s-app: default-http-backend
spec:
  ports:
  - port: 80
    targetPort: 8080
  selector:
    k8s-app: default-http-backend


创建：


$ kubectl create -f default-backend.yaml 
deployment "default-http-backend" created
service "default-http-backend" created



创建之后查看：

root@ubuntu15:/data/ingress# kubectl get rs,pod,svc  -n kube-system 
NAME                                 DESIRED   CURRENT   READY     AGE
rs/default-http-backend-857b544d94   1         1         1         1m


NAME                                       READY     STATUS    RESTARTS   AGE
po/default-http-backend-857b544d94-bwgjd   1/1       Running   0          1m


NAME                       TYPE        CLUSTER-IP       EXTERNAL-IP   PORT(S)         AGE
svc/default-http-backend   ClusterIP   10.254.208.144   <none>        80/TCP          1m


创建好default backend后就要创建nginx-ingress-controller了：



$ cat nginx-ingress-controller.yaml 
apiVersion: extensions/v1beta1
kind: Deployment
metadata:
  name: nginx-ingress-controller
  labels:
    k8s-app: nginx-ingress-controller
  namespace: kube-system
spec:
  replicas: 1
  template:
    metadata:
      labels:
        k8s-app: nginx-ingress-controller
    spec:
      # hostNetwork makes it possible to use ipv6 and to preserve the source IP correctly regardless of docker configuration
      # however, it is not a hard dependency of the nginx-ingress-controller itself and it may cause issues if port 10254 already is taken on the host
      # that said, since hostPort is broken on CNI (https://github.com/kubernetes/kubernetes/issues/31307) we have to use hostNetwork where CNI is used
      # like with kubeadm
      # hostNetwork: true #注释表示不使用宿主机的80口，
      terminationGracePeriodSeconds: 60
      hostNetwork: true  #表示容器使用和宿主机一样的网络
      serviceAccountName: nginx-ingress-serviceaccount #引用前面创建的serviceacount
      containers:   
      - image: gcr.io/google_containers/nginx-ingress-controller:0.9.0-beta.1      #容器使用的镜像
        name: nginx-ingress-controller  #容器名
        readinessProbe:   #启动这个服务时要验证/healthz 端口10254会在运行的node上监听。 
          httpGet:
            path: /healthz
            port: 10254
            scheme: HTTP
        livenessProbe:
          httpGet:
            path: /healthz
            port: 10254
            scheme: HTTP
          initialDelaySeconds: 10  #每隔10做健康检查 
          timeoutSeconds: 1
        ports:
        - containerPort: 80  
          hostPort: 80    #80映射到80
        - containerPort: 443
          hostPort: 443
        env:
          - name: POD_NAME
            valueFrom:
              fieldRef:
                fieldPath: metadata.name
          - name: POD_NAMESPACE
            valueFrom:
              fieldRef:
                fieldPath: metadata.namespace
        args:
        - /nginx-ingress-controller
        - --default-backend-service=$(POD_NAMESPACE)/default-http-backend
#        - --default-ssl-certificate=$(POD_NAMESPACE)/ingress-secret    #这是启用Https时用的
      nodeSelector:  #指明运行在哪，此IP要和default backend是同一个IP
        kubernetes.io/hostname: 10.3.1.17   #上面映射到了hostport80，确保此IP80，443没有占用.



 这个控制器就是一个deployment ，里面运行一个容器gcr.io/google_containers/nginx-ingress-controller:0.9.0-beta.1 ，有点像nginx容器，现在创建：

$ kubectl create -f nginx-ingress-controller.yaml 
deployment "nginx-ingress-controller" created
 
  
root@ubuntu15:/data/ingress# kubectl get rs,pod,svc  -n kube-system 
NAME                                     DESIRED   CURRENT   READY     AGE
rs/default-http-backend-857b544d94       1         1         1         12m
rs/nginx-ingress-controller-8576d4545d   1         1         0         27s

NAME                                           READY     STATUS              RESTARTS   AGE
po/default-http-backend-857b544d94-bwgjd       1/1       Running             0          12m
po/nginx-ingress-controller-8576d4545d-9tjnv   0/1       ContainerCreating   0          27s

NAME                       TYPE        CLUSTER-IP       EXTERNAL-IP   PORT(S)         AGE
svc/default-http-backend   ClusterIP   10.254.208.144   <none>        80/TCP          12m


   现在ingress controller 控制器已部署好了，那么如何使用了，那就要写一个ingress规则了，此处就以已存在的jenkins服务为例，配置如何使用域名访问这个service:


$ kubectl get svc,ep
NAME                  TYPE        CLUSTER-IP       EXTERNAL-IP   PORT(S)          AGE
svc/jenkinsservice    NodePort    10.254.70.47     <none>        8080:30002/TCP   3h


NAME                 ENDPOINTS                                         AGE
ep/jenkinsservice    172.30.10.15:8080,172.30.11.7:8080                3h



   现在写个jenkins service的Ingress 规则：


$ cat jenkins-ingress.yml 
apiVersion: extensions/v1beta1
kind: Ingress
metadata:
  name: jenkins-ingress
  namespace: default #服务在哪个空间内就写哪个空间
  annotations:
    kubernetes.io/ingress.class: "nginx"
spec:
  rules:
  - host: ingress.jenkins.com   #此service的访问域名
    http:
      paths:
      - backend:
          serviceName: jenkinsservice  
          servicePort: 8080



 创建它：


$ kubectl create -f jenkins-ingress.yml 
ingress "jenkins-ingress" created

$ kubectl get ingress 
NAME              HOSTS                 ADDRESS   PORTS     AGE
jenkins-ingress   ingress.jenkins.com             80        10s


  

 到这里就已经部署完成了，配置好域名后，就可以用此域名来访问了：

  

k8s的ingress 请求到service 负载不均衡 k8s配置ingress_后端_03


  部署完成了，现在看下nginx-ingress-controller 里nginx配置文件发生了哪些变化：


upstream default-jenkinsservice-8080 {
        least_conn;
        server 172.30.10.15:8080 max_fails=0 fail_timeout=0;
        server 172.30.11.7:8080 max_fails=0 fail_timeout=0;
    }
    upstream upstream-default-backend {
        least_conn;
        server 172.30.11.6:8080 max_fails=0 fail_timeout=0;
    }
 
 server {
        server_name ingress.jenkins.com;
        listen [::]:80;

        location / {
            ...
            proxy_pass http://default-jenkinsservice-8080;
            ...
        }
    }


   这些配置都是ingress-controller 自已写入的，动态更新就是它能通过K8S API感知到service的endpoint 发生了变化，然后修改nginx配置并执行reload.

   至此，部署完成。

   Ingress还有很多部署方式，比如配置https访问的, 以后再写。


转载于:https://blog.51cto.com/newfly/2060587