4.1.2 PATH based routing in NGINX Ingress Controller

PATH-based basic routing test

This is the most basic routing, and the routing service is different according to the URL PATH.

1. Deploy the sample app for testing.

   Deploy two web pages with different background colors.

   kubectl create deployment nginx-blue --image=thekoguryo/nginx-hello:blue
   kubectl expose deployment nginx-blue --name nginx-blue-svc --port 80
   kubectl create deployment nginx-green --image=thekoguryo/nginx-hello:green
   kubectl expose deployment nginx-green --name nginx-green-svc --port 80
   

2. Write the ingress setup YAML (path-basic.yaml).

   • /blue requests are routed to nginx-blue-svc
   • /green requests are routed to nginx-green-svc

   apiVersion: networking.k8s.io/v1
   kind: Ingress
   metadata:
     name: ingress-path-basic
     annotations:
       kubernetes.io/ingress.class: nginx
   spec:
     rules:
     - http:
         paths:
         - path: /blue
           pathType: Prefix
           backend:
             service:
               name: nginx-blue-svc
               port:
                 number: 80
     - http:
         paths:
         - path: /green
           pathType: Prefix
           backend:
             service:
               name: nginx-green-svc
               port:
                 number: 80
   

3. Deploy the created path-basic.yaml.

   $ kubectl apply -f path-basic.yaml 
   ingress.networking.k8s.io/ingress-path-basic created
   $ kubectl get ingress
   NAME                 CLASS    HOSTS   ADDRESS           PORTS   AGE
   ingress-path-basic   <none>   *       132.226.225.240   80      49s
   

4. Connect to the EXTERNAL IP of the ingress controller checked earlier and check the result.

   • request /blue

     

   • request /green

     

   • Check POD information

     According to the defined PATH, you can see that the blue and green apps are routed to the deployed POD, respectively, with the web page background color and POD IP.

     $ kubectl get pod -o wide
     NAME                           READY   STATUS    RESTARTS   AGE   IP             NODE          NOMINATED NODE   READINESS GATES
     nginx-blue-6fccd8fb49-q6qph    1/1     Running   0          13m   10.244.0.138   10.0.10.139   <none>           <none>
     nginx-green-7f646c5c7f-snpxf   1/1     Running   0          13m   10.244.0.5     10.0.10.84    <none>           <none>
     

Rewrite Target

If you look at the URL PATH routing result, you can see that the paths of /blue and /green are finally routed and delivered to the running app. It is used only for routing in the ingress controller, and is used when modifications are necessary for the actual operation of the app.

• https://kubernetes.github.io/ingress-nginx/examples/rewrite/

1. Write the ingress setup YAML (path-rewrite-target.yaml).

   • path: /blue -> /blue(/|$)(.*)
   • Add annotation: nginx.ingress.kubernetes.io/rewrite-target: /$2
   • example
     • ~~/blue -> passed to the app with ~~/
     • ~~/blue/abc -> passed to the app as ~~/abc

   apiVersion: networking.k8s.io/v1
   kind: Ingress
   metadata:
     name: ingress-path-rewrite-target
     annotations:
       kubernetes.io/ingress.class: nginx
       nginx.ingress.kubernetes.io/rewrite-target: /$2
   spec:
     rules:
     - http:
         paths:
         - path: /blue(/|$)(.*)
           pathType: Prefix
           backend:
             service:
               name: nginx-blue-svc
               port:
                 number: 80
     - http:
         paths:
         - path: /green(/|$)(.*)
           pathType: Prefix
           backend:
             service:
               name: nginx-green-svc
               port:
                 number: 80
   

2. Delete the preceding path-basic.yaml and deploy path-rewrite-target.yaml.

   $ kubectl delete -f path-basic.yaml 
   ingress.networking.k8s.io "ingress-path-basic" deleted
   $ kubectl apply -f path-rewrite-target.yaml 
   ingress.networking.k8s.io/ingress-path-rewrite-target created
   $ kubectl get ingress
   NAME                          CLASS    HOSTS   ADDRESS           PORTS   AGE
   ingress-path-rewrite-target   <none>   *       132.226.225.240   80      43s
   

3. Connect to the EXTERNAL IP of the ingress controller checked earlier and check the result.

   • request ~~/blue

     • In routed apps, /blue is missing and only received by /

     

   • Request ~~/blue/abc

     • In routed apps, /blue is missing and only received by /abc