Ingress介绍
每个Service都要有一个负载均衡服务,所以这个做法实际上既浪费成本又高.作为用户,更希望看到Kubernetes为我内置一个全局的负载均衡器.然后,通过我访问的 URL,把请求转发给不同的后端 Service.这种全局的,为了代理不同后端Service而设置的负载均衡服务,就是Kubernetes里的Ingress服务
所以Ingress的功能其实很容易理解:所谓 Ingress,就是 Service 的Service
Ingress和Service的区别:
Ingress负载均衡的后端应用是由众多Service组成的集合 本质是一个7层调度器(通过url,http,https协议进行调度)
Servie负载均衡的后端应用是由众多Pod组成的集合 本质是一个4层调度器(iptables,ipvs进行IP包转发)
使用Kubernetes的Ingress来创建一个统一的负载均衡器,从而实现当用户访问不同的域名时,能够访问到不同的Deployment
最值得我们关注的,是 rules 字段.在 Kubernetes 里 这个字段叫作:IngressRule
IngressRule的Key就叫做:host.它必须是一个标准的域名格式(Fully Qualified Domain Name)的字符串,而不能是IP地址
cafe.example.com 的时候,实际上访问到的是这个Ingress对象.这样Kubernetes 就能使用IngressRule来对你的请求进行下一步转发
Ingress Contronl控制器
Ingress Controller会根据你定义的Ingress对象,提供对应的代理能力.目前,业界常用的各种反向代理项目Nginx、HAProxy、Envoy、Traefik 等都已经为Kubernetes专门维护了对应的Ingress Controller
一个Nginx Ingress Controller为你提供的服务,其实是一个可以根据Ingress对象和被代理后端Service的变化,来自动进行更新的Nginx负载均衡器
Ingress只能工作在七层,而 Service只能工作在四层.所以当你想要在k8s里为应用进行TLS配置等HTTP相关的操作时都必须通过Ingress来进行
Ingress Controller是一个拥有运行七层调度的应用程序的Pod(比如运行一个NGINX的服务的Pod) nginx pod通过url映射来把请求代理不同的Pod
外部用戶跟Ingress Controller管理的Pod采用https协议进行通信 Ingress Controller管理的Pod跟被它代理的其它Pod采用http协议通信
Ingress Controller管理的Pod实现了https会话卸载器的功能
Ingress资源
1.首先通过无头service动态关联符合标签选择器选择的后端Pod
2.Ingress动态的把service关联的pod地址注入到前端配置upstream中 同时触发主程序重新加载最新的配置文件
pod变化 > service变化 > Ingress变化 > Ingress Control注入配置
1.Pod的数量或者IP发生变化的时候通过selector选择Pod的service会自动更新
2.因为Service是无头service类型 所以访问service的时候获取的不是VIP而是service被代理的Pod地址集合
3.Ingress资源通过Service资源的变化自动维护提供upstream的后端Pod集合
4.Ingress自动更新配置文件 通知nginx主进程重载最新的配置文件
Ingress部署实例
1.部署一个Ingress Control 比如nginx的Pod
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 "<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: 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:0.28.0
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
# www-data -> 101
runAsUser: 101
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
View Code
2.部署nodeport的service用来为ingress-controller的pod提供访问入口接入集群外部流量
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
- name: https
port: 443
targetPort: 443
protocol: TCP
selector:
app.kubernetes.io/name: ingress-nginx
app.kubernetes.io/part-of: ingress-nginx
---
View Code
3.定义Pod和service 并通过selector把service和pod关联起来
Ingress Control的pod中nginx有多少组upstream就需要定义多少个headless service来关联不同的pod
apiVersion: apps/v1
kind: Deployment
metadata:
name: coffee
spec:
replicas: 2
selector:
matchLabels:
app: coffee
template:
metadata:
labels:
app: coffee
spec:
containers:
- name: coffee
image: nginxdemos/hello:plain-text
ports:
- containerPort: 80
---
apiVersion: v1
kind: Service
metadata:
name: coffee-svc
spec:
ports:
- port: 80
targetPort: 80
protocol: TCP
name: http
selector:
app: coffee
---
apiVersion: apps/v1
kind: Deployment
metadata:
name: tea
spec:
replicas: 3
selector:
matchLabels:
app: tea
template:
metadata:
labels:
app: tea
spec:
containers:
- name: tea
image: nginxdemos/hello:plain-text
ports:
- containerPort: 80
---
apiVersion: v1
kind: Service
metadata:
name: tea-svc
labels:
spec:
ports:
- port: 80
targetPort: 80
protocol: TCP
name: http
selector:
app: tea
View Code
4.定义一个Ingress资源关联servie
apiVersion: extensions/v1beta1
kind: Ingress
metadata:
name: cafe-ingress
namespace: default
annotations:
kubernetes.io/ingress.class: "nginx"
spec:
rules:
- host: yxh.example.com
http:
paths:
- path: /tea
backend:
serviceName: tea-svc
servicePort: 80
- path: /coffee
backend:
serviceName: coffee-svc
servicePort: 80
View Code
5.配置DNS解析
IngressRule的Key,就叫做:host.它必须是一个标准的域名格式(Fully Qualified Domain Name)的字符串而不能是IP地址 修改hosts
6.测试负载效果
集群外客户端通过访问nodeport的serive端口->Ingress Control(nginx) ->读取最新nginx.conf找Pod(根据不同的url转发到不同的Pod) -> Pod