Ingress: 入口，负责统一管理外部对k8s cluster中service的请求。通过定义Ingress Resoucre（Ingress，Ingress Controller，Ingress Service）等实现。
internet
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[ Ingress ]
--|-----|--
[ Services ]使用Ingress的好处：
1. 端口管理。减少不必要端口暴露，便于管理。
所有的请求，通过Ingress对应的IP：PORT进入，过滤/转发/负载均衡到相应的service/pod。
k8s现在提供三种暴露服务的方式：LoadBlancer、NodePort 、Ingress。
NodePort会在每个node上暴露对应的port，不便管理。
2. 动态配置服务
以Ingress Nignx为例，实现原理如下。
Ingress Contronler 通过与 Kubernetes API 交互，能够动态的获取cluster中Ingress rules的变化，生成一段 Nginx 配置，再写到 Nginx-ingress-control的 Pod 里，reload pod 使规则生效。从而实现注册的service及其对应域名/IP/Port的动态添加和解析。
Demo：
1. 配置ingress
apiVersion: extensions/v1beta1
kind: Ingress
metadata:
name: ingress-nginx
annotations:
nginx.ingress.kubernetes.io/rewrite-target: /
spec:
rules:
- host: java-application.local
http:
paths:
- path: /spring-boot-demo
backend:
serviceName: spring-boot-demo
servicePort: 8080（注：java-application.local是配置的指向k8s所在IP的域名，eg: minikube环境下，指向minikube ip, 访问 java-application.local：30001/spring-boot-demo 即可访问 spring-boot-demo service）
2. 配置ingress controller及configmap（ingress nginx通过读取configmap 和annotations中的配置来配置nginx
kind: ConfigMap
apiVersion: v1
metadata:
name: nginx-configuration
namespace: spring-boot-demo
labels:
app: ingress-nginx
---
kind: ConfigMap
apiVersion: v1
metadata:
name: tcp-services
namespace: spring-boot-demo
---
kind: ConfigMap
apiVersion: v1
metadata:
name: udp-services
namespace: spring-boot-demo
---
apiVersion: apps/v1
kind: Deployment
metadata:
name: nginx-ingress-controller
namespace: spring-boot-demo
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
app: ingress-nginx
template:
metadata:
labels:
app.kubernetes.io/name: ingress-nginx
app.kubernetes.io/part-of: ingress-nginx
app: ingress-nginx
annotations:
prometheus.io/port: "10254"
prometheus.io/scrape: "true"
spec:
serviceAccountName: nginx-ingress-serviceaccount
containers:
- name: nginx-ingress-controller
image: quay.io/kubernetes-ingress-controller/nginx-ingress-controller:0.23.0
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
runAsUser: 33
env:
- name: POD_NAME
valueFrom:
fieldRef:
fieldPath: metadata.name
- name: POD_NAMESPACE
valueFrom:
fieldRef:
fieldPath: metadata.namespace
ports:
- name: http
containerPort: 80
- name: https
containerPort: 443
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
---3. 配置相关权限，从而使ingress resouce可以访问API Server，获取相关cluster/service/pod信息
apiVersion: v1
kind: ServiceAccount
metadata:
name: nginx-ingress-serviceaccount
namespace: spring-boot-demo
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:
- "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
namespace: spring-boot-demo
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 "<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
---
apiVersion: rbac.authorization.k8s.io/v1beta1
kind: RoleBinding
metadata:
name: nginx-ingress-role-nisa-binding
namespace: spring-boot-demo
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: spring-boot-demo
---
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: spring-boot-demo
---
4. 配置ingress service
apiVersion: v1
kind: Service
metadata:
name: ingress-nginx
namespace: spring-boot-demo
spec:
type: NodePort
ports:
- name: http
port: 80
targetPort: 80
protocol: TCP
nodePort: 30001
selector:
app: ingress-nginxRefs:
https://kubernetes.io/docs/concepts/services-networking/ingress/
https://kubernetes.io/docs/concepts/services-networking/ingress-controllers/
https://kubernetes.io/docs/reference/generated/kubernetes-api/v1.13/#podtemplatelist-v1-core
https://kubernetes.github.io/ingress-nginx/deploy/
https://github.com/kubernetes/ingress-nginx/blob/master/deploy/configmap.yaml
https://www.cnblogs.com/ericnie/p/6965091.html
（Traefik针对k8s有更多预定义集成配置，需要自己配置的内容大大减少）