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Kubernetes

We are running a Kubernetes cluster on top of CloudStack. Each member gets their own namespace in which they can deploy their applications.

Info

If you wish to learn about how to operate a Kubernetes cluster, you may create your own cluster using software such as k3s. If all you want to do is run some containerized apps, then we suggest that you use our cluster instead, since it has far more resources.

Account resource limits

As of this writing, the per-namespace Kubernetes resource limits for each member are:

  • 40 pods
  • 10 jobs
  • 10 cron jobs
  • 25 GB of Persistent Volume Claims
  • 5 NodePort services

If you wish to acquire more resources, please send an email to the Systems Committee with a brief justification.

Info

LoadBalancer services are disabled because we are running our own load balancer (NGINX) outside of Kubernetes which we manage ourselves. See Exposing your app, below.

Create a new namespace

Log into a general-use machine and run the following: 

ceo k8s account activate

This will create a new Kubernetes namespace whose name has the format csc-username. A new kubeconfig file will be placed into ~/.kube/config. To verify that everything is working properly, run the following command: 

kubectl cluster-info

The output should look something like this: 

Kubernetes control plane is running at https://172.19.134.149:6443
CoreDNS is running at https://172.19.134.149:6443/api/v1/namespaces/kube-system/services/kube-dns:dns/proxy

To further debug and diagnose cluster problems, use 'kubectl cluster-info dump'.

Quickstart

So, let's say you've created a Dockerized app, and the image is available on some publicly available registry such as Docker Hub or Quay.io. Here is the bare minimum which you need to do get your app running in our Kubernetes cluster.

First, create a Deployment: 

kubectl create deployment demo --image=ctdalek/myapp --port=80
Replace the values of --image and --port as necessary.

If your app does not need to be publicly exposed, then you are done; otherwise, you need to create a Service to expose your Deployment: 

kubectl expose deployment demo

Finally, create an Ingress which exposes the Service to the outside world: 

kubectl create ingress demo --rule='ctdalek.k8s.csclub.cloud/*=demo:80'

You should now be able to access your app at e.g. https://ctdalek.k8s.csclub.cloud.

To see what kind of Ingress domains you may create, see Ingress domains below.

Not-so-quick start

At this point I am going to take the lazy way out and direct you to the official Kubernetes documentation:

You may also contact the Systems Committee for assistance if something is not working the way you think it should.

Exposing your app

If your app is running in our Kuberenetes cluster, you have two options for exposing it to the outside world: an Ingress (preferred), or a NodePort. We generally recommend using an Ingress if your program is a web application; for non-web apps, you will need to use a NodePort instead. Since our Kubernetes cluster is not publicly accessible, the NodePort will only be directly accessible from on-campus.

Ingress domains

By default, you may only create Ingress rules of the form username.k8s.csclub.cloud or *-username.k8s.csclub.cloud. If you wish to use a custom domain, please contact the Systems Committee.

If you decide to create a multi-level subdomain (e.g. app.ctdalek.k8s.csclub.cloud), then you will also need to create a corresponding virtual host (see Virtual Hosting) which points to k8s. For example: 

ceo cloud vhosts add app.ctdalek.k8s.csclub.cloud k8s

We strongly encourage you to use single-level subdomains instead (e.g. app-ctdalek.k8s.csclub.cloud) since this does not require us to obtain a new SSL certificate.