Kubernetes Ingress Controller的使用及高可用落地

Kubernetes Ingress Controller的使用及高可用落地

看懂本文要具备一下知识点:

  • Service实现原理和会应用

  • 知道反向代理原理,了解nginx和apache的vhost概念

  • 了解service的几种类型(Nodeport、clusterip、LB)

  • 四层和七层区别(不明白就这样去理解,七层最常见就是应用层的http,也就是url,四层是传输层,为tcp/udp端口)

  • 域名解析,/etc/hosts等基础知识

Ingress Controller介绍

Ingress Controller是一个统称,并不是只有一个,有如下这些:

  • Ingress NGINX: Kubernetes 官方维护的方案,也是本次安装使用的 Controller。

  • F5 BIG-IP Controller: F5 所开发的 Controller,它能够让管理员通过 CLI 或 API 让 Kubernetes 与 OpenShift 管理 F5 BIG-IP 设备。

  • Ingress Kong: 著名的开源 API Gateway 方案所维护的 Kubernetes Ingress Controller。

  • Traefik: 是一套开源的 HTTP 反向代理与负载均衡器,而它也支援了 Ingress。

  • Voyager: 一套以 HAProxy 为底的 Ingress Controller。

Ingress Controller 的实现不只上面这些方案,还有很多可以在网络上找到这里不一一列出来了。

我们部署在集群里的服务的svc想暴露出来的时候,从长久眼光看和易于管理维护都是用的Ingress Controller来处理,clusterip非集群主机无法访问,Nodeport不方便长久管理和效率,LB服务多了不方便因为需要花费额外的钱,externalIPS不好用(后面有空写文章会说它)。

我们跑的大多服务都是应用层http(s),Ingress Controller使用service或者pod的网络将它暴露在集群外,然后它反向代理集群内的七层服务,通过vhost子域名那样路由到后端的服务,Ingress Controller工作架构如下,借用traefik官方的图。

Kubernetes Ingress Controller的使用及高可用落地

你可以将api.domain.com进来的流量路由到集群里api的pod,你可以将backoffice.domain.com流量路由到backoffice的一组pod上,虽说我们可以自己搭建一个nginx来代替掉Ingress Controller,但是要增加代理的service长期来看维护很不方便,在使用上Ingress Controller后可以用一种抽象的对象告诉controller添加对应的代理,也就是kind: Ingress。它里面描述了从Ingress Controller访问进来的ServerName和web的url要代理到集群里哪个service(以及service的port)等等具体信息。

而官方的Ingress Nginx可以视为一个魔改的nginx,拥有集群赋予的RBAC权限后,能够有监听集群Ingress相关的变化能力,用户创建了kind: Ingress, 例如上面trafik图里的Ingress大致就是下面这样:

apiVersion: extensions/v1beta1
kind: Ingress
metadata:
name: my-ingress
annotations:
nginx.ingress.kubernetes.io/use-regex: "true"
spec:
rules:
- host: api.mydomain.com
http:
paths:
- backend:
serviceName: api
servicePort: 80
- host: domain.com
http:
paths:
- path: /web/*
backend:
serviceName: web
servicePort: 8080
- host: backoffice.domain.com
http:
paths:
- backend:
serviceName: backoffice
servicePort: 8080

只要创建了上面的Ingress后,ingress controller里会监听到从而生成对应的配置段后动态reload配置文件。

Ingress Controller部署

部署非常简单,一条命令创建即可,yml来源于 https://github.com/kubernetes/ingress-nginx/tree/master/deploy

kubectl apply -f https://raw.githubusercontent.com/kubernetes/ingress-nginx/master/deploy/mandatory.yaml

该yaml缺少向群外暴露的方式,ingress-controller需要开启 hostNetwork: true便于暴漏ingress的80端口和其他ingress-controller的nginx.conf暴漏的端口

下面提供一个修改好验证可用的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:
- "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: 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: 2
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:
serviceAccountName: nginx-ingress-serviceaccount
hostNetwork: true
containers:
- name: nginx-ingress-controller
image: hejianlai/nginx-ingress-controller:0.23.0
args:
- /nginx-ingress-controller
- --default-backend-service=$(POD_NAMESPACE)/default-http-backend
- --configmap=$(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
- 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 ---

上面的yaml里后面详细解释我们需要关注的配置项,先来创建ingress对象试试。

测试http 7层负载

部署了官方的ingress nginx后,我部署了一个nginx的pod,为它创建了一个名为nginx的service:

apiVersion: extensions/v1beta1
kind: Deployment
metadata:
name: nginx
spec:
template:
metadata:
labels:
app: nginx
spec:
containers:
- image: nginx
name: nginx
ports:
- containerPort: 80
---
apiVersion: v1
kind: Service
metadata:
name: nginx
spec:
selector:
app: nginx
ports:
- protocol: TCP
port: 80
targetPort: 80

然后创建对应的一个ingress对象来暴露集群里这个nginx的http服务:

apiVersion: extensions/v1beta1
kind: Ingress
metadata:
name: nginx-ingress
spec:
rules:
- host: nginx.testdomain.com
http:
paths:
- backend:
serviceName: nginx
servicePort: 80

查看ingress资源

[root@master k8s_yaml]# kubectl get ingress
NAME HOSTS ADDRESS PORTS AGE
app-nginx-ingress nginx.testdomain.com 80 3d

找到ingress nginx的pod名字后通过命令查看里面nginx配置文件能找到有对应的配置段生成:

$ kubectl -n ingress-nginx exec nginx-ingress-controller-6cdcfd8ff9-t5sxl -- cat /etc/nginx/nginx.conf
...
## start server nginx.testdomain.com
server {
server_name nginx.testdomain.com ;

listen 80;

set $proxy_upstream_name "-";

location / {

set $namespace "default";
set $ingress_name "nginx-ingress";
set $service_name "nginx";
set $service_port "80";
set $location_path "/";
........
## end server nginx.testdomain.com
...

找一台非集群的Windows机器(也可以mac,主要是有图形界面且非集群内机器),设置hosts文件把域名nginx.testdomain.com设置到对service的那个node的ip上,打开浏览器访问nginx.testdomain.com即可发现集群内的nginx已经暴露在集群外。

注意:Ingress Controller虽然调用的是service,看起来按照nginx来理解转发是client–nginx–svc–pod; 实际上转发是client–nginx–pod,因为已经魔改了不能按照nginx的来理解,是直接负载到svc的endpoint上面的。

另外低版本的ingress nginx的args参数--default-backend-service=$(POD_NAMESPACE)/default-http-backend,该参数指定ingress nginx的同namespace下名为default-http-backend的service作为默认访问的时候页面,通常那个时候是创建一个404页面的的pod和对应service,如果ingress nginx启动的时候没找到这个service会无法启动,新版本不是必须了,好像也自带404页面了。

下面是default-http-backend.yaml:

apiVersion: extensions/v1beta1
kind: Deployment
metadata:
name: default-http-backend
labels:
app: default-http-backend
namespace: ingress-nginx
spec:
replicas: 1
template:
metadata:
labels:
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:1.4
livenessProbe:
httpGet:
path: /healthz
port: 8080
scheme: HTTP
initialDelaySeconds: 30
timeoutSeconds: 5
ports:
- containerPort: 8080
resources:
limits:
cpu: 10m
memory: 20Mi
requests:
cpu: 10m
memory: 20Mi
--- apiVersion: v1
kind: Service
metadata:
name: default-http-backend
namespace: ingress-nginx
labels:
app: default-http-backend
spec:
ports:
- port: 80
targetPort: 8080
selector:
app: default-http-backend

另外ingress也能多路径,如下:

apiVersion: networking.k8s.io/v1beta1
kind: Ingress
metadata:
name: simple-fanout-example
annotations:
nginx.ingress.kubernetes.io/rewrite-target: /
spec:
rules:
- host: foo.bar.com
http:
paths:
- path: /foo
backend:
serviceName: service1
servicePort: 4200
- path: /bar
backend:
serviceName: service2
servicePort: 8080

 注:nginx.ingress.kubernetes.io/rewrite-target: /

如何来4层负载

我们可以看到ingress nginx的args里有这两行:

- --tcp-services-configmap=$(POD_NAMESPACE)/tcp-services
- --udp-services-configmap=$(POD_NAMESPACE)/udp-services

从选项和值可以猜测出,要想代理四层(tcp/udp),得写同namespace里一个名为tcp-serviceudp-service的两个configmap的数据 四层的话这边我们创建一个mysql的pod,来代理3306端口到集群外面,则需要写tcp-services这个configmap:

kind: ConfigMap
apiVersion: v1
metadata:
name: tcp-services
namespace: ingress-nginx
data:
3306: "default/mysql:3306"

四层写这两个ConfigMap的data即可,按照这样去写即可out_port: namespaces/svc_name:port,要给每个ingress加一些nginx里的配置可以查看官方的annotation字段以及值(traefik同理)。

Ingress Controller高可用

这里来讨论下Ingress Controller的高可用。

Ingress Controller到集群内的路径这部分都有负载均衡了,我们比较关注部署了Ingress Controller后,外部到它这段路怎么高可用?

上面的例子里service我使用的externalIPs,但是代理四层的时候会新加端口,需要每次人为去介入增加暴露端口?

流量从入口到Ingress Controller的pod有下面几种方式:

  • type为LoadBalancer的时候手写externalIPs很鸡肋,后面会再写文章去讲它

  • type为LoadBalancer的时候只有云厂商支持分配公网ip来负载均衡,LoadBalancer 公开的每项服务都将获得自己的 IP 地址,但是需要收费,且自己建立集群无法使用

  • 不创建service,pod直接用hostport,效率等同于hostNetwork,如果不代理四层端口还好,代理了需要修改pod的template来滚动更新来让nginx bind的四层端口能映射到宿主机上

  • Nodeport,端口不是web端口(但是可以修改Nodeport的范围改成web端口),如果进来流量负载到Nodeport上可能某个流量路线到某个node上的时候因为Ingress Controller的pod不在这个node上,会走这个node的kube-proxy转发到Ingress Controller的pod上,多走一趟路

  • 不创建service,效率最高,也能四层负载的时候不修改pod的template,唯一要注意的是hostNetwork下pod会继承宿主机的网络协议,也就是使用了主机的dns,会导致svc的请求直接走宿主机的上到公网的dns服务器而非集群里的dns server,需要设置pod的dnsPolicy: ClusterFirstWithHostNet即可解决

写在最后

部署方式没多大区别开心就好。

  • DaemonSet + nodeSeletor

  • deploy设置replicas数量 + nodeSeletor + pod互斥

  • 所以可以一个vip飘在拥有存活的controller的宿主机上,云上的话就用slb来负载代替vip

  • 最后说说域名请求指向它,如果部署在内网或者办公室啥的,内网有dns server的话把ing的域名全部解析到ingress controller的宿主机ip上,否则要有人访问每个人设置/etc/hosts才能把域名解析来贼麻烦,如果没有dns server可以跑一个external-dns,它的上游dns是公网的dns服务器,办公网内机器的dns server指向它即可,云上的话把域名请求解析到对应ip即可

  • traefik和ingress nginx类似,不过它用go实现的

  • 在一些老版本的ingress nginx的log里会一直刷找不到ingress-nginx的svc,不处理的话会狂刷log导致机器load过高,创建一个同名的svc即可解决,例如创建一个不带选择器clusterip为null的即可。非要创建port的svc的话参照下面:

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: ClusterIP
ports:
- name: http
port: 80
targetPort: 80
protocol: TCP
- name: https
port: 443
targetPort: 443
protocol: TCP
- name: metrics
port: 10254
targetPort: 10254
protocol: TCP
selector:
app.kubernetes.io/name: ingress-nginx
app.kubernetes.io/part-of: ingress-nginx
 
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