上一篇文章介绍了 ingress vhost这个annotation的使用，趁热打铁我们一口气介绍 9 个常用的annotation。

1、ingress class

如果一个k8s 集群里面部署多个ingress controller的时候，如果配置ingress 希望指定到某个ingress controller的时候，ingress claas就发挥巨大作用了。

一方面在controller启动的时候需要通过参数指定ingress class

--ingress-class=ngx-ds

另一方面，在创建ingress的时候，通过annotation指定ingress class，如下所示

apiVersion: extensions/v1beta1
kind: Ingress
metadata:
  name: other-ngx-k8s
  namespace: other-ngx
  annotations:
    kubernetes.io/ingress.class: "ngx-ds"
spec:
  rules:
  - host: other-ngx-k8s.demo.com.cn
    http:
      paths:
      - path: /
        backend:
          serviceName: other-ngx-k8s-ngx-svc
          servicePort: 9001

2、 强制https

nginx.ingress.kubernetes.io/force-ssl-redirect: "true"通过这个annotation可以强制 https，如果是http请求，会通过 301 redirect到 https。

apiVersion: networking.k8s.io/v1beta1
kind: Ingress
metadata:
  name: test-ingress
  annotations:
    nginx.ingress.kubernetes.io/rewrite-target: /
    nginx.ingress.kubernetes.io/force-ssl-redirect: "true"
    nginx.ingress.kubernetes.io/ssl-redirect: "true"
    nginx.ingress.kubernetes.io/preserve-trailing-slash: "true"
spec:
  rules:
  - http:
      paths:
      - path: /testpath
        backend:
          serviceName: test
          servicePort: 80

3、请求超时

nginx.org/proxy-connect-timeout 和nginx.org/proxy-read-timeout 这两个参数分别设置nginx的建立连接以及等待结果的超时时间。

apiVersion: networking.k8s.io/v1beta1
kind: Ingress
metadata:
  name: cafe-ingress-with-annotations
  annotations:
    nginx.org/proxy-connect-timeout: "30s"
    nginx.org/proxy-read-timeout: "20s"
spec:
  rules:
  - host: cafe.example.com
    http:
      paths:
      - path: /tea
        backend:
          serviceName: tea-svc
          servicePort: 80
      - path: /coffee
        backend:
          serviceName: coffee-svc
          servicePort: 80

4、跨域访问

我们经常将nginx作为api的网关，支持跨域必不可少。通过nginx.ingress.kubernetes.io/cors-allow-methods 设置支持跨域请求的方法。

apiVersion: networking.k8s.io/v1beta1
kind: Ingress
metadata:
  name: test-ingress
  annotations:
    nginx.ingress.kubernetes.io/enable-cors: "true"
    nginx.ingress.kubernetes.io/cors-allow-methods: "PUT, GET, POST, OPTIONS"
    nginx.ingress.kubernetes.io/cors-allow-headers: "X-Forwarded-For, X-app123-XPTO"
    nginx.ingress.kubernetes.io/cors-expose-headers: "*, X-CustomResponseHeader"
    nginx.ingress.kubernetes.io/cors-max-age: 600
    nginx.ingress.kubernetes.io/cors-allow-credentials: "false"
spec:
  rules:
  - http:
      paths:
      - path: /testpath
        backend:
          serviceName: test
          servicePort: 80

5、限流

限流也经常使用，通过 rps 限制每秒请求数，rpm 限制每分钟请求数，connections限制连接数。

apiVersion: networking.k8s.io/v1beta1
kind: Ingress
metadata:
  name: test-ingress
  annotations:
    nginx.ingress.kubernetes.io/limit-rps: "5"
    nginx.ingress.kubernetes.io/limit-rpm: "300"
    nginx.ingress.kubernetes.io/limit-connections: "10"
spec:
  rules:
  - http:
      paths:
      - path: /testpath
        backend:
          serviceName: test
          servicePort: 80

6、最大body

这个主要是针对外部请求，防止将流量打满，proxy-body-size 设置最大请求 body，如果超过则会返回 413 请求错误。

apiVersion: networking.k8s.io/v1beta1
kind: Ingress
metadata:
  name: test-ingress
  annotations:
    nginx.ingress.kubernetes.io/proxy-body-size: 8m
spec:
  rules:
  - http:
      paths:
      - path: /testpath
        backend:
          serviceName: test

7、客户端白名单

这个主要是用于安全限制，只允许特定的客户端请求，但由于现在网络中NAT的广泛应用，这个参数使用的场景比较有限。

apiVersion: networking.k8s.io/v1beta1
kind: Ingress
metadata:
  name: test-ingress
  annotations:
     ingress.kubernetes.io/whitelist-source-range: "10.0.0.0/24,172.10.0.1"
spec:
  rules:
  - http:
      paths:
      - path: /testpath
        backend:
          serviceName: test

8、默认服务

这个经常使用，当客户端请求一个不存在的path的时候，我们不希望返回 404 ，跳转到一个默认的服务上。

apiVersion: networking.k8s.io/v1beta1
kind: Ingress
metadata:
  name: test-ingress
  annotations:
     nginx.ingress.kubernetes.io/default-backend: <svc name>
spec:
  rules:
  - http:
      paths:
      - path: /testpath
        backend:
          serviceName: test

9、access log开关

nginx ingress 默认是开启access log的，如果你想关闭，可以通过将 nginx.ingress.kubernetes.io/enable-access-log 设置成false。

apiVersion: networking.k8s.io/v1beta1
kind: Ingress
metadata:
  name: test-ingress
  annotations:
     nginx.ingress.kubernetes.io/enable-access-log: "false"
spec:
  rules:
  - http:
      paths:
      - path: /testpath
        backend:
          serviceName: test