OK, first of all, let me make sure that you understand what we are trying to do here.

Let us say that I have a lot of kubernetes services with names like below. This list may grow or shrink dynamically and is controlled by some other script.

I am spinning up a dev instances for each use as they login. Something new I am working on.

exper-0 exper-1 exper-2 exper-3 exper-4

Now if I do not wanna create separate ingress for each item, how would I go about doing this?

Heads Up. You cannot use default nginx ingress for this.

Architecture # (https://blog.meain.io/2020/dynamic-reverse-proxy-kubernetes/#architecture) Here is an overview of how we do this.

• Create a custom nginx deployment with a specific nginx.conf injected using a configmap.

• Create a service which will expose this custom nginx deployment

• Define an ingress with *.mydomain.com mapped to this service

With this setup we will have exper-0.mydomain.com pointing to exper-0.

Code # (https://blog.meain.io/2020/dynamic-reverse-proxy-kubernetes/#code) Now, going about actually doing it.

nginx.conf and configmap.yaml # (https://blog.meain.io/2020/dynamic-reverse-proxy-kubernetes/#nginx.conf-and-configmap.yaml) As we discussed above we need to define a custom nginx conf. This part is expained here. The essence of your nginx conf is:

server { listen 80;

server_name ~^(?.*?).; resolver kube-dns.kube-system.svc.cluster.local valid=5s;

location / { proxy_pass http://$subdomain.mynamespace.svc.cluster.local; proxy_set_header Host \(host; } } Replace mynamespace with the namespace you have this thing in Let me explain what is going on. • You listen on port 80. Basic. • For servername, you have a regex that will pull the first block of hostname to subdomain. This gets used a few lines down. • You have to specify a resolver as nginx has to resolve this into and actual IP(internal IP of svc). • Now, inside location block you grab everything and pass it over to http://\)subdomain.mynamespace.svc.cluster.local which will resolve to the IP of the service.

• You also need to change Host as otherwise it will be set as http://$subdomain.mynamespace.svc.cluster.local instead of exper-0.mydomain.com.

We actually need a bit more sutff to support websocket.

proxy_set_header Upgrade $http_upgrade; proxy_set_header Connection “Upgrade”; Add in a healthcheck.

location /healthz { return 200; } With all that in, it will look something like this.

server { listen 80;

server_name ~^(?.*?).; resolver kube-dns.kube-system.svc.cluster.local valid=5s;

location /healthz { return 200; }

location / { proxy_set_header Upgrade \(http_upgrade; proxy_set_header Connection "Upgrade"; proxy_pass http://\)subdomain.msce0.svc.cluster.local; proxy_set_header Host \(host; } } We will also have to add some root config as we have to write a complete nginx.conf. Pull all that together and drop it into a configmap.yaml and we have our first kubernetes object. configmap.yaml apiVersion: v1 kind: ConfigMap metadata: name: confnginx data: nginx.conf: | user nginx; worker_processes 1; error_log /var/log/nginx/error.log warn; pid /var/run/nginx.pid; events { worker_connections 1024; } http { include /etc/nginx/mime.types; default_type application/octet-stream; log_format main '\)remote_addr - \(remote_user [\)time_local] “\(request" ' '\)status \(body_bytes_sent "\)http_referer” ’ ‘“\(http_user_agent" "\)http_x_forwarded_for”’; access_log /var/log/nginx/access.log main; sendfile on; keepalive_timeout 65; server { listen 80;

    server_name ~^(?<subdomain>.*?)\.;
    resolver kube-dns.kube-system.svc.cluster.local valid=5s;

    location /healthz {
      return 200;
    }

    location / {
      proxy_set_header Upgrade \(http_upgrade;
          proxy_set_header Connection "Upgrade";
          proxy_pass http://\)subdomain.msce0.svc.cluster.local;
      proxy_set_header Host $host;
      proxy_http_version 1.1;
    }
  }
}

deployment.yaml and service.yaml # (https://blog.meain.io/2020/dynamic-reverse-proxy-kubernetes/#deployment.yaml-and-service.yaml) There is nothing fancy in here. Just a plain old deployment.yaml and service.yaml.

Inside deployment.yaml we have to make sure to load the configmap we setup. See the volumeMounts section.

deployment.yaml

apiVersion: apps/v1 kind: Deployment metadata: name: nginx labels: app: nginx spec: selector: matchLabels: app: nginx replicas: 1 template: metadata: labels: app: nginx spec: containers: - name: nginx image: nginx:alpine ports: - containerPort: 80 volumeMounts: - name: nginx-config mountPath: /etc/nginx/nginx.conf subPath: nginx.conf volumes: - name: nginx-config configMap: name: confnginx service.yaml

kind: Service apiVersion: v1 metadata: name: nginx-custom spec: selector: app: nginx ports:

• protocol: TCP port: 80 targetPort: 80 name: nginx ingress.yaml # (https://blog.meain.io/2020/dynamic-reverse-proxy-kubernetes/#ingress.yaml) Now with the service setup, we can use an ingress to give it a hostname.

ingress.yaml

apiVersion: networking.k8s.io/v1beta1 kind: Ingress metadata: name: ingress-nginx-custom annotations: kubernetes.io/ingress.class: nginx spec: rules:

• host: ‘*.mydomain.com’ http: paths:
  • path: / backend: serviceName: nginx-custom servicePort: 80 Deploy # (https://blog.meain.io/2020/dynamic-reverse-proxy-kubernetes/#deploy) Well, I am pretty sure you know how to do this. But essentially

k apply -f configmap.yaml k apply -f deployment.yaml k apply -f service.yaml k apply -f ingress.yaml K. THX. BYE