Kubernetes ingress for dynamic URL - kubernetes

Question

I am developing an application that allows users to play around in their own sandboxes with a finite life time. Conceptually, it can be thought as if users were playing games of Pong. Users can interact with a web interface hosted at main/ to start a game of Pong. Each game of Pong will exist in its own pod. Since each game has a finite lifetime, the pods are dynamically created on-demand (through the Kubernetes API) as Kubernetes jobs with a single pod. There is therefore a one-to-one relationship between games of Pong and pods. Up to this point I have it all figured out.
My problem is, how do I set up an ingress to map dynamically created URLs, for example main/game1, to the corresponding pods? That is, if a user starts a game through the main interface, I would like him to be redirected to the URL of the corresponding pod where his game is hosted.
I could pre-allocate a set of urls, check if they have active jobs, and redirect if they do not, but the does not scale well. I am thinking dynamically assigning URLs is a common pattern in Kubernetes, so there must be a standard way to do this. I have looked at using nginx-ingress, but that is not a requirement.

Answer 1

Furthermore the comment, I created for you a little demo on minikube providing a working Ingress Class controller (enabled via minikube addons enable ingress).
Replicating the multiple Deployment that simulates the games.
kubectl create deployment deployment-1 --image=nginxdemos/hello
kubectl create deployment deployment-2 --image=nginxdemos/hello
kubectl create deployment deployment-3 --image=nginxdemos/hello
kubectl create deployment deployment-4 --image=nginxdemos/hello
kubectl create deployment deployment-5 --image=nginxdemos/hello
Same for Services resources:
kubectl create service clusterip deployment-1 --tcp=80:80
kubectl create service clusterip deployment-2 --tcp=80:80
kubectl create service clusterip deployment-3 --tcp=80:80
kubectl create service clusterip deployment-4 --tcp=80:80
kubectl create service clusterip deployment-5 --tcp=80:80
Finally, it's time for the Ingress one but we have to be quite hacky since we don't have the subcommand create available.
for number in `seq 5`; do echo "
apiVersion: networking.k8s.io/v1beta1
kind: Ingress
metadata:
name: deployment-$number
annotations:
nginx.ingress.kubernetes.io/rewrite-target: /$1
spec:
rules:
- host: hello-world.info
http:
paths:
- path: /game$number
backend:
serviceName: deployment-$number
servicePort: 80
" | kubectl create -f -; done
Now you have Pod, Service and Ingress: obviously, you have to replicate the same result using Kubernetes API but, as I suggested in the comment, you should create a single Ingress resource and update accordingly Path subkey in a dynamic way.
However, if you try to simulate the cURL call faking the Host header, you can see the working result:
# curl `minikube ip`/game2 -sH 'Host: hello-world.info'|grep -i server
<p><span>Server address:</span> <span>172.17.0.5:80</span></p>
<p><span>Server name:</span> <span>deployment-2-5b98b954f6-8g5fl</span></p>
# curl `minikube ip`/game4 -sH 'Host: hello-world.info'|grep -i server
<p><span>Server address:</span> <span>172.17.0.7:80</span></p>
<p><span>Server name:</span> <span>deployment-4-767ff76774-d2fgj</span></p>
You can see the Pod IP and name as well.

Answer 2

I agree with Efrat Levitan. It's not the task for ingress/kubernetes itself.
You need another application (different layer of abstraction) to distinguish where the traffic should be routed for example istio and Routing rule for HTTP traffic based on cookies.