08 . Kubernetes之 ingress及Ingress Controller

Ingress简介

ingress是什么？

上篇文章介绍service时有说了暴露了service的三种方式ClusterIP、NodePort与LoadBalance，这几种方式都是在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的变化，更新endpoint中对应pod的对象，提供了ip不断变化的pod的服务发现机制，对集群外部，他类似负载均衡器，可以在集群内外部对pod进行访问。但是，单独用service暴露服务的方式，在实际生产环境中不太合适：

ClusterIP的方式只能在集群内部访问

NodePort方式的话，测试环境使用还行，当有几十上百的服务在集群中运行时，NodePort的端口管理是灾难。

LoadBalance方式受限于云平台，且通常在云平台部署ELB还需要额外的费用。

所幸k8s还提供了一种集群维度暴露服务的方式，也就是ingress。ingress可以简单理解为service的service，他通过独立的ingress对象来制定请求转发的规则，把请求路由到一个或多个service中。这样就把服务与请求规则解耦了，可以从业务维度统一考虑业务的暴露，而不用为每个service单独考虑。

举个例子，现在集群有api、文件存储、前端3个service，可以通过一个ingress对象来实现图中的请求转发

)

Ingress规则是很灵活的，可以根据不同域名，不同path转发请求到不同的service，并且支持https/http.

Ingress与Ingress-controller

要理解ingress,需要区分两个概念，ingress和ingress-controller:

Ingress对象:

指的是k8s中的一个api对象，一般用yaml配置，作用是定义请求如何转发到service的规则，可以理解为配置模板;

Ingress-controller

具体实现反向代理及负载均衡的程序，对ingress定义的规则进行解析，根据配置的规则来实现请求转发;
简单来说，Ingress-controller才是负责转发的组件，通过各种方式将他暴露在集群入口，外部对集群的请求流量会先到Ingress-controller,而Ingress对象是用来告诉Ingress-controller该如何转发请求，比如那些域名那些path要转发到那些服务等.

Ingress-controller

# 他跟Deployment等控制器不一样，其他控制器都属于Master三大组件之一，而Ingress是独立的一个控制器.  
# Nginx  
# Trefik （微服务）  
# Envoy  

Ingress-controller并不是k8s自带的组件，实际上ingress-controller只是一个统称，用户可以选择不同的Ingress-controller实现，目前，由K8S维护的Ingress-controller只有google云的GCE与Ingress-nginx两个，其他还有第三方维护的ingress-controller,但不管采用哪种Ingress-controller,实现的机制都大同小异，只是在具体配置上有差异，一般来说，Ingress-controller的形式都是一个Pod，里面跑着daemon程序和反向代理程序，daemon负责不断监控集群的变化，根据Ingress对象生成配置并应用新配置到反向代理，比如nginx-ingress就是动态生成nginx配置，动态更新upstream，并在需要视乎reload程序应用新配置，为了方便，后面的例子都已k8s官方维护的nginx-ingress为例.

Ingress应用

Ingress是一个API对象，和其他对象一样，通过yaml文件来配置，Ingress通过http或https暴露集群内部service，给service提供外部URL、负载均衡、SSL/TLS能力以及基于host的方向代理，Ingress要依靠Ingress-controller来具体实现以上功能.大概就是如下配置:

apiVersion: extensions/v1beta1
kind: Ingress
metadata:
  name: abc-ingress
  annotations: 
    kubernetes.io/ingress.class: "nginx"
    nginx.ingress.kubernetes.io/use-regex: "true"
spec:
  tls:
  - hosts:
    - api.abc.com
    secretName: abc-tls
  rules:
  - host: api.abc.com
    http:
      paths:
      - backend:
          serviceName: apiserver
          servicePort: 80
  - host: www.abc.com
    http:
      paths:
      - path: /image/*
        backend:
          serviceName: fileserver
          servicePort: 80
  - host: www.abc.com
    http:
      paths:
      - backend:
          serviceName: feserver
          servicePort: 8080

与其他k8s对象一样，ingress配置也包含了apiVersion、kind、meatdata、spec等关键字段，有几个关注的spec字段中，tls用于定义https密钥、证书。rule用于指定请求路由规则，这里指的关注的是metadata.annotations字段，在ingress配置中，annotations很重要，前面有说ingress-controller有很多不同的实现，而不同的Ingress-controller就可以根据"kubernetes.io/ingress.class"来判断要使用那些ingress配置，同时，不同的ingress-controller也有对应的annotations配置，用于自定义一些参数，例如上面配置的'nginx.ingress.kubernetes.io/use-regex: "true"',最终是在生成nginx配置中，会采用location ~来表示正则匹配

Ingress部署

Ingress的部署，需要考虑两个方面:

# 1 . ingress-controller是作为Pod来运行的，以什么方式部署比较好
# 2 . ingress解决了如何请求路由到集群内部，那他自己怎么暴露给外部比较好

下面列举一些目前常用的部署和暴露方式，具体使用哪种方式还得根据实际需要考虑来决定

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。

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，一般会在前面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。

DaemonSet+HostNetwork+nodeSelector

用DaemonSet结合nodeselector来部署ingress-controller到特定的node上，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。

for file in configmap.yaml namespace.yaml mandatory.yaml rbac.yaml with-rbac.yaml; do wget https://github.com/kubernetes/ingress-nginx/tree/master/deploy/static/$file ;done

cat mandatory.yaml
apiVersion: v1
kind: Namespace
metadata:
  name: ingress-nginx
  labels:
    app.kubernetes.io/name: ingress-nginx
    app.kubernetes.io/part-of: ingress-nginx

---

kind: ConfigMap
apiVersion: v1
metadata:
  name: nginx-configuration
  namespace: ingress-nginx
  labels:
    app.kubernetes.io/name: ingress-nginx
    app.kubernetes.io/part-of: ingress-nginx

---
kind: ConfigMap
apiVersion: v1
metadata:
  name: tcp-services
  namespace: ingress-nginx
  labels:
    app.kubernetes.io/name: ingress-nginx
    app.kubernetes.io/part-of: ingress-nginx

---
kind: ConfigMap
apiVersion: v1
metadata:
  name: udp-services
  namespace: ingress-nginx
  labels:
    app.kubernetes.io/name: ingress-nginx
    app.kubernetes.io/part-of: ingress-nginx

---
apiVersion: v1
kind: ServiceAccount
metadata:
  name: nginx-ingress-serviceaccount
  namespace: ingress-nginx
  labels:
    app.kubernetes.io/name: ingress-nginx
    app.kubernetes.io/part-of: ingress-nginx

---
apiVersion: rbac.authorization.k8s.io/v1beta1
kind: ClusterRole
metadata:
  name: nginx-ingress-clusterrole
  labels:
    app.kubernetes.io/name: ingress-nginx
    app.kubernetes.io/part-of: ingress-nginx
rules:
  - apiGroups:
      - ""
    resources:
      - configmaps
      - endpoints
      - nodes
      - pods
      - secrets
    verbs:
      - list
      - watch
  - apiGroups:
      - ""
    resources:
      - nodes
    verbs:
      - get
  - apiGroups:
      - ""
    resources:
      - services
    verbs:
      - get
      - list
      - watch
  - apiGroups:
      - ""
    resources:
      - events
    verbs:
      - create
      - patch
  - apiGroups:
      - "extensions"
      - "networking.k8s.io"
    resources:
      - ingresses
    verbs:
      - get
      - list
      - watch
  - apiGroups:
      - "extensions"
      - "networking.k8s.io"
    resources:
      - ingresses/status
    verbs:
      - update

---
apiVersion: rbac.authorization.k8s.io/v1beta1
kind: Role
metadata:
  name: nginx-ingress-role
  namespace: ingress-nginx
  labels:
    app.kubernetes.io/name: ingress-nginx
    app.kubernetes.io/part-of: ingress-nginx
rules:
  - apiGroups:
      - ""
    resources:
      - configmaps
      - pods
      - secrets
      - namespaces
    verbs:
      - get
  - apiGroups:
      - ""
    resources:
      - configmaps
    resourceNames:
      # Defaults to "-"
      # Here: "-"
      # 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

---
apiVersion: rbac.authorization.k8s.io/v1beta1
kind: RoleBinding
metadata:
  name: nginx-ingress-role-nisa-binding
  namespace: ingress-nginx
  labels:
    app.kubernetes.io/name: ingress-nginx
    app.kubernetes.io/part-of: ingress-nginx
roleRef:
  apiGroup: rbac.authorization.k8s.io
  kind: Role
  name: nginx-ingress-role
subjects:
  - kind: ServiceAccount
    name: nginx-ingress-serviceaccount
    namespace: ingress-nginx

---
apiVersion: rbac.authorization.k8s.io/v1beta1
kind: ClusterRoleBinding
metadata:
  name: nginx-ingress-clusterrole-nisa-binding
  labels:
    app.kubernetes.io/name: ingress-nginx
    app.kubernetes.io/part-of: ingress-nginx
roleRef:
  apiGroup: rbac.authorization.k8s.io
  kind: ClusterRole
  name: nginx-ingress-clusterrole
subjects:
  - kind: ServiceAccount
    name: nginx-ingress-serviceaccount
    namespace: ingress-nginx

---

apiVersion: apps/v1
kind: Deployment
metadata:
  name: nginx-ingress-controller
  namespace: ingress-nginx
  labels:
    app.kubernetes.io/name: ingress-nginx
    app.kubernetes.io/part-of: ingress-nginx
spec:
  replicas: 1
  selector:
    matchLabels:
      app.kubernetes.io/name: ingress-nginx
      app.kubernetes.io/part-of: ingress-nginx
  template:
    metadata:
      labels:
        app.kubernetes.io/name: ingress-nginx
        app.kubernetes.io/part-of: ingress-nginx
      annotations:
        prometheus.io/port: "10254"
        prometheus.io/scrape: "true"
    spec:
      # wait up to five minutes for the drain of connections
      terminationGracePeriodSeconds: 300
      serviceAccountName: nginx-ingress-serviceaccount
      nodeSelector:
        kubernetes.io/os: linux
      containers:
        - name: nginx-ingress-controller
          image: quay.io/kubernetes-ingress-controller/nginx-ingress-controller:0.26.1
          args:
            - /nginx-ingress-controller
            - --configmap=$(POD_NAMESPACE)/nginx-configuration
            - --tcp-services-configmap=$(POD_NAMESPACE)/tcp-services
            - --udp-services-configmap=$(POD_NAMESPACE)/udp-services
            - --publish-service=$(POD_NAMESPACE)/ingress-nginx
            - --annotations-prefix=nginx.ingress.kubernetes.io
          securityContext:
            allowPrivilegeEscalation: true
            capabilities:
              drop:
                - ALL
              add:
                - NET_BIND_SERVICE
            # www-data -> 33
            runAsUser: 33
          env:
            - name: POD_NAME
              valueFrom:
                fieldRef:
                  fieldPath: metadata.name
            - name: POD_NAMESPACE
              valueFrom:
                fieldRef:
                  fieldPath: metadata.namespace
          ports:
            - name: http
              containerPort: 80
              protocol: TCP
            - name: https
              containerPort: 443
              protocol: TCP
          livenessProbe:
            failureThreshold: 3
            httpGet:
              path: /healthz
              port: 10254
              scheme: HTTP
            initialDelaySeconds: 10
            periodSeconds: 10
            successThreshold: 1
            timeoutSeconds: 10
          readinessProbe:
            failureThreshold: 3
            httpGet:
              path: /healthz
              port: 10254
              scheme: HTTP
            periodSeconds: 10
            successThreshold: 1
            timeoutSeconds: 10
          lifecycle:
            preStop:
              exec:
                command:
                  - /wait-shutdown

---

apiVersion: v1
kind: LimitRange
metadata:
  name: ingress-nginx
  namespace: ingress-nginx
  labels:
    app.kubernetes.io/name: ingress-nginx
    app.kubernetes.io/part-of: ingress-nginx
spec:
  limits:
  - default:
    min:
      memory: 90Mi
      cpu: 100m
    type: Container


kubectl apply -f mandatory.yaml 
kubectl get pod -n ingress-nginx
NAME                                        READY   STATUS    RESTARTS   AGE
nginx-ingress-controller-568867bf56-wwgqx   1/1     Running   0          4m10s

如果是裸机的话需要创建一个Nodeport暴露端口

https://kubernetes.github.io/ingress-nginx/deploy/#bare-metal

wget https://raw.githubusercontent.com/kubernetes/ingress-nginx/master/deploy/static/provider/baremetal/service-nodeport.yaml

# 为了让暴露端口不是随机的，我们指定一下.
cat service-nodeport.yaml 
apiVersion: v1
kind: Service
metadata:
  name: ingress-nginx
  namespace: ingress-nginx
  labels:
    app.kubernetes.io/name: ingress-nginx
    app.kubernetes.io/part-of: ingress-nginx
spec:
  type: NodePort
  ports:
    - name: http
      port: 80
      targetPort: 80
      protocol: TCP
      nodePort: 30080
    - name: https
      port: 443
      targetPort: 443
      protocol: TCP
      nodePort: 30443
  selector:
    app.kubernetes.io/name: ingress-nginx
    app.kubernetes.io/part-of: ingress-nginx
---
kubectl apply -f service-nodeport.yaml
kubectl get svc -n ingress-nginx
NAME            TYPE       CLUSTER-IP      EXTERNAL-IP   PORT(S)                      AGE
ingress-nginx   NodePort   10.96.120.168           80:30080/TCP,443:30443/TCP   6m19s

# 我们使用集群外的一台机器访问看一下

接下来我们将之前的myapp应用给发布出去

cat ingress-myapp.yaml 
apiVersion: extensions/v1beta1
kind: Ingress
metadata:
  name: ingress-myapp
  namespace: default
  annotations:
    kubernetes.io/ingress.class: "nginx"
spec:
  rules:
  - host: myapp.youmen.com
    http:
      paths:
      - path:
        backend:
          serviceName: redis
          servicePort: 80 
kubectl apply -f ingress-myapp.yaml
# 我们一旦创建ingress就会立刻将环境注入到nginx
kubectl exec -n ingress-nginx -it nginx-ingress-controller-568867bf56-wwgqx /bin/bash
cat nginx.conf  |grep youmen
	## start server myapp.youmen.com
		server_name myapp.youmen.com ;
	## end server myapp.youmen.com

# 接下来我们去修改本地主机的hosts文件
Windows:  C:\Windows\System32\drivers\etc
Linux: /etc/hosts
172.19.0.26    myapp.youmen.com
# 浏览器访问即可出现下面页面

发布Tomcat应用(http)

创建tomcatDeployment和service

cat tomcat-deploy.yaml 
apiVersion: v1
kind: Service
metadata:
  name: tomcat
  namespace: default
spec:
  selector:
    app: tomcat
    release: canary
  ports:
  - name: http
    targetPort: 8080
    port: 8080

  - name: ajp
    targetPort: 8009
    port: 8009

---
apiVersion: apps/v1
kind: Deployment
metadata:
  name: tomcat-deploy
  namespace: default
spec:
  replicas: 3
  selector:
    matchLabels:
      app: tomcat
      release: canary
  template:
    metadata:
      labels:
        app: tomcat
        release: canary
    spec:
      containers:
      - name: tomcat 
        image: tomcat:8.5.32-jre8-alpine
        ports:
        - name: http
          containerPort: 8080
        - name: ajp
          containerPort: 8009

创建Ingress-tomcat.yaml

cat ingress-tomcat.yaml 
apiVersion: extensions/v1beta1
kind: Ingress
metadata:
  name: ingress-tomcat
  namespace: default
  annotations:
    kubernetes.io/ingress.class: "nginx"
spec:
  rules:
  - host: tomcat.youmen.com
    http:
      paths:
      - path:
        backend:
          serviceName: tomcat
          servicePort: 8080
# 跟上面步骤一样做域名解析,然后访问浏览器IP:30080

https加密tomcat

# mkdir encryption
# cd encryption
openssl genrsa -out tls.key 2048
# Generating RSA private key, 2048 bit long modulus
# .............................+++
# ...+++
# e is 65537 (0x10001)
openssl req -new -x509 -key tls.key -out tls.crt \
  -subj /C=CN/ST=Beijing/L=Beijing/O=DevOps/CN=tomcat.youmen.com
ls
# tls.crt  tls.key

# 我们用来https加密的证书不能直接放到Pod需要将他转换成secret格式，他也是一个k8s对象.
kubectl create secret tls tomcat-ingress-secret --cert=tls.crt --key=tls.key

kubectl get secret
NAME                    TYPE                                  DATA   AGE
default-token-j9thc     kubernetes.io/service-account-token   3      5d23h
tomcat-ingress-secret   kubernetes.io/tls                     2      6s

kubectl describe secret tomcat-ingress-secret
Name:         tomcat-ingress-secret
Namespace:    default
Labels:       
Annotations:  
Type:  kubernetes.io/tls
Data
====
tls.crt:  1294 bytes
tls.key:  1675 bytes

cat ingress-tomcat-tls.yaml 
apiVersion: extensions/v1beta1
kind: Ingress
metadata:
  name: ingress-tomcat-tls
  namespace: default
  annotations:
    kubernetes.io/ingress.class: "nginx"
spec:
  tls:
  - hosts:
    - tomcat.youmen.com
    secretName: tomcat-ingress-secret
  rules:
  - host: tomcat.youmen.com
    http:
      paths:
      - path:
        backend:
          serviceName: tomcat
          servicePort: 8080

apply Ingress-tomcat-tls.yaml

kubectl describe ingress ingress-tomcat-tls
Name:             ingress-tomcat-tls
Namespace:        default
Address:          10.96.120.168
Default backend:  default-http-backend:80 ()
TLS:
  tomcat-ingress-secret terminates tomcat.youmen.com
Rules:
  Host               Path  Backends
  ----               ----  --------
  tomcat.youmen.com  
                        tomcat:8080 (10.244.1.45:8080,10.244.1.46:8080,10.244.2.35:8080)
Annotations:
  kubectl.kubernetes.io/last-applied-configuration:  {"apiVersion":"extensions/v1beta1","kind":\
"Ingress","metadata":{"annotations":{"kubernetes.io/ingress.class":"nginx"},"name":"\
ingress-tomcat-tls","namespace":"default"},"spec":{"rules":[{"host":"tomcat.youmen.com",\
"http":{"paths":[{"backend":{"serviceName":"tomcat","servicePort":8080},"path":null}]}}],\
"tls":[{"hosts":["tomcat.youmen.com"],"secretName":"tomcat-ingress-secret"}]}}

  kubernetes.io/ingress.class:  nginx
Events:
  Type    Reason  Age        From                      Message
  ----    ------  ----       ----                      -------
  Normal  CREATE    nginx-ingress-controller  Ingress default/ingress-tomcat-tls
  Normal  UPDATE    nginx-ingress-controller  Ingress default/ingress-tomcat-tls

kubectl get secret
NAME                    TYPE                                  DATA   AGE
default-token-j9thc     kubernetes.io/service-account-token   3      5d23h
tomcat-ingress-secret   kubernetes.io/tls                     2      10m

# 我们去ingress-nginx查看一下证书有没有注入进来
kubectl exec -n ingress-nginx -it  nginx-ingress-controller-568867bf56-wwgqx  /bin/bash
www-data@nginx-ingress-controller-5688f56-wwgqx:/etc/nginx$ cat nginx.conf |grep ssl_certificate_*
	ssl_certificate     /etc/ingress-controller/ssl/default-fake-certificate.pem;
	ssl_certificate_key /etc/ingress-controller/ssl/default-fake-certificate.pem;

# 接下来浏览器访问https//域名:30443即可