Kubernetes kind: Ingress - Uygulamaya Http ve DNS İsmiyle Erişim Sağlar

Giriş

Açıklaması şöyle

An API object that manages external access to the services in a cluster, typically HTTP. Ingress may provide load balancing, SSL termination and name-based virtual hosting.

Uygulamaya abc.com şeklinde erişebilmeyi sağlar. Yani path based routing yapar

Not : minikube ile bir örnek burada

Ingress ve API Gateway

Ingress genellikle proprietary (sağlayıcıya tescilli) şeyler kullanmayı gerektiriyor. Bunu istemiyorsak, üçüncü bir taraf tarafından sağlanan ve daha standard olan bir API Gateway kullanılabilir. Mesela SIG-NETWORK topluluğu bir standard sağlıyor ve Apache APISIX bu standardı geçekleştirenlerden bir tanesi.

Ingress Neden Lazım?

Açıklaması şöyle. Yani tek bir Ingress ile bir sürü uygulamaya erişimi sağlanabilir.

Ingress is a more capable version of a service. We need a service for each of our applications when we use a LoadBalancer service. For example, if we have 8 apps, then we need 8 services. This is not cost-efficient. With Ingress, we expose multiple services with a single LoadBalancer service.

So how does Ingress know which service to route traffic to? How does it know we want to access user service, not invoice service? Ingress uses host-based and path-based routing for that.

Ingressleri görmek için şöyle yaparız

kubectl get ingress

TLS

Açıklaması şöyle

You can secure an Ingress by specifying a Secret that contains a TLS private key and certificate. The Ingress resource only supports a single TLS port, 443, and assumes TLS termination at the ingress point (traffic to the Service and its Pods is in plaintext). If the TLS configuration section in an Ingress specifies different hosts, they are multiplexed on the same port according to the hostname specified through the SNI TLS extension (provided the Ingress controller supports SNI).

Load balancing

Açıklaması şöyle

An Ingress controller is bootstrapped with some load balancing policy settings that it applies to all Ingress, such as the load balancing algorithm, backend weight scheme, and others. More advanced load balancing concepts (e.g. persistent sessions, dynamic weights) are not yet exposed through the Ingress. You can instead get these features through the load balancer used for a Service. 

Ingress Çeşitleri

İki çeşit Ingress var. Bunlar şöyle

1. Path Based veya Simple Fanout

2. Host Based veya Name based virtual hosting

1. Path Based veya Simple Fanout

Path Based Routing yazısına taşıdım

2. Host Based veya Name based virtual hosting

Birden fazla host ismi vardır. Http isteğindeki "Host başlığına" göre yönlendirilir

Örnek

Şöyle yaparız

apiVersion: networking.k8s.io/v1
kind: Ingress
metadata:
  name: name-virtual-host-ingress
spec:
  rules:
  - host: foo.bar.com
    http:
      paths:
      - pathType: Prefix
        path: "/"
        backend:
          service:
            name: service1
            port:
              number: 80
  - host: bar.foo.com
    http:
      paths:
      - pathType: Prefix
        path: "/"
        backend:
          service:
            name: service2
            port:
              number: 80

Örnek

Şöyle yaparız. Uygulamaya keycloak.demo.com ve application.demo.com şeklinde erişebiliriz.

kind: Ingress
apiVersion: networking.k8s.io/v1
metadata:
  name: backendingress
  namespace: spring-keycloak-demo
  annotations:
    kubernetes.io/ingress.class: nginx
    nginx.ingress.kubernetes.io/ssl-redirect: "false"
    nginx.ingress.kubernetes.io/rewrite-target: /
spec:
  tls:
    - hosts:
        - keycloak.demo.com
        - application.demo.com
  rules:
    - host: keycloak.demo.com
      http:
        paths:
          - path: /
            pathType: Prefix
            backend:
              service:
                name: spring-keycloak-demo
                port:
                  number: 8080
    - host: application.demo.com
      http:
          paths:
              - path: /
                pathType: Prefix
                backend:
                  service:
                    name: backend-service
                    port:
                      number: 8000

Örnek

Şöyle yaparız. user.localhost ve order.localhost  şeklinde erişebiliriz.

apiVersion: networking.k8s.io/v1
kind: Ingress
metadata:
  name: ingress-host-based
  annotations:
    nginx.ingress.kubernetes.io/rewrite-target: /
spec:
  ingressClassName: nginx
  rules:
    - host: order.localtest.me
      http:
        paths:
          - path: /
            pathType: Prefix
            backend:
              service:
                name: order-service
                port:
                  number: 8080
    - host: user.localtest.me
      http:
        paths:
          - path: /
            pathType: Prefix
            backend:
              service:
                name: user-service
                port:
                  number: 8080