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Nginx Ingress Controller for Kubernetes - the "flux way"

The Nginx Ingress Controller is the grandpappy of Ingress Controllers, with releases dating back ot at least 2016. Of course, Nginx itself is a battle-tested rock, released in 2004 and has been constantly updated / improved ever since.

Having such a pedigree though can make it a little awkward for the unfamiliar to configure Nginx, whereas something like Traefik, being newer-on-the-scene, is more user-friendly, and offers (among other features) a free dashboard. (Nginx's dashboard is only available in the commercial Nginx+ package, which is a monumental PITA to run)

Nginx Ingress Controller does make for a nice, simple "default" Ingress controller, if you don't want to do anything fancy.

Ingredients

Optional:

  • Cert-Manager deployed to request/renew certificates
  • External DNS configured to respond to ingresses, or with a wildcard DNS entry

Preparation

Namespace

We need a namespace to deploy our HelmRelease and associated ConfigMaps into. Per the flux design, I create this example yaml in my flux repo at bootstrap/namespaces/namespace-nginx-ingress-controller.yaml:

Example NameSpace (click to expand) 
apiVersion: v1
kind: Namespace
metadata:
  name: nginx-ingress-controller

HelmRepository

Next, we need to define a HelmRepository (a repository of helm charts), to which we'll refer when we create the HelmRelease. We only need to do this once per-repository. In this case, we're using the (prolific) bitnami chart repository, so per the flux design, I create this example yaml in my flux repo at bootstrap/helmrepositories/helmrepository-bitnami.yaml:

Example HelmRepository (click to expand) 
apiVersion: source.toolkit.fluxcd.io/v1beta1
kind: HelmRepository
metadata:
  name: bitnami
  namespace: flux-system
spec:
  interval: 15m
  url: https://charts.bitnami.com/bitnami

Kustomization

Now that the "global" elements of this deployment (Namespace and HelmRepository) have been defined, we do some "flux-ception", and go one layer deeper, adding another Kustomization, telling flux to deploy any YAMLs found in the repo at /nginx-ingress-controller. I create this example Kustomization in my flux repo at bootstrap/kustomizations/kustomization-nginx-ingress-controller.yaml:

Example Kustomization (click to expand) 
apiVersion: kustomize.toolkit.fluxcd.io/v1
kind: Kustomization
metadata:
  name: nginx-ingress-controller
  namespace: flux-system
spec:
  interval: 15m
  path: ./nginx-ingress-controller
  prune: true # remove any elements later removed from the above path
  timeout: 2m # if not set, this defaults to interval duration, which is 1h
  sourceRef:
    kind: GitRepository
    name: flux-system
  healthChecks:
    - apiVersion: apps/v1
      kind: Deployment
      name: nginx-ingress-controller
      namespace: nginx-ingress-controller

ConfigMap

Now we're into the nginx-ingress-controller-specific YAMLs. First, we create a ConfigMap, containing the entire contents of the helm chart's values.yaml. Paste the values into a values.yaml key as illustrated below, indented 4 spaces (since they're "encapsulated" within the ConfigMap YAML). I create this example yaml in my flux repo at nginx-ingress-controller/configmap-nginx-ingress-controller-helm-chart-value-overrides.yaml:

Example ConfigMap (click to expand) 
apiVersion: v1
kind: ConfigMap
metadata:
  creationTimestamp: null
  name: nginx-ingress-controller-helm-chart-value-overrides
  namespace: nginx-ingress-controller
data:
  values.yaml: |-
    # paste chart values.yaml (indented) here and alter as required

That's a lot of unnecessary text!

Why not just paste in the subset of values I want to change?

You know what's harder than working out which values from a 2000-line values.yaml to change?

Answer: Working out what values to change when the upstream helm chart has refactored or added options! By pasting in the entirety of the upstream chart, when it comes time to perform upgrades, you can just duplicate your ConfigMap YAML, paste the new values into one of the copies, and compare them side by side to ensure your original values/decisions persist in the new chart.

Then work your way through the values you pasted, and change any which are specific to your configuration. It may not be necessary to change anything.

HelmRelease

Lastly, having set the scene above, we define the HelmRelease which will actually deploy nginx-ingress-controller into the cluster, with the config and extra ConfigMap we defined above. I save this in my flux repo as nginx-ingress-controller/helmrelease-nginx-ingress-controller.yaml:

Example HelmRelease (click to expand) 
apiVersion: helm.toolkit.fluxcd.io/v2beta1
kind: HelmRelease
metadata:
  name: nginx-ingress-controller
  namespace: nginx-ingress-controller
spec:
  chart:
    spec:
      chart: nginx-ingress-controller
      version: 9.x
      sourceRef:
        kind: HelmRepository
        name: bitnami
        namespace: flux-system
  interval: 15m
  timeout: 5m
  releaseName: nginx-ingress-controller
  valuesFrom:
  - kind: ConfigMap
    name: nginx-ingress-controller-helm-chart-value-overrides
    valuesKey: values.yaml # This is the default, but best to be explicit for clarity
Why not just put config in the HelmRelease?

While it's true that we could embed values directly into the HelmRelease YAML, this becomes unweildy with large helm charts. It's also simpler (less likely to result in error) if changes to HelmReleases, which affect deployment of the chart, are defined in separate files to changes in helm chart values, which affect operation of the chart.

Deploy nginx-ingress-controller

Having committed the above to your flux repository, you should shortly see a nginx-ingress-controller kustomization, and in the nginx-ingress-controller namespace, the expected pods happily running:

demo@shredder:~$ kubectl get pods -n nginx-ingress-controller
NAME                                                        READY   STATUS    RESTARTS   AGE
nginx-ingress-controller-5b849b4fbd-svbxk                   1/1     Running   0          24h
nginx-ingress-controller-5b849b4fbd-xt7vc                   1/1     Running   0          24h
nginx-ingress-controller-default-backend-867d86fb8f-t27j9   1/1     Running   0          24h
demo@shredder:~$

How do I know it's working?

Test Service

By default, the chart will deploy nginx ingress controller's service in LoadBalancer mode. When you use kubectl to display the service (kubectl get services -n nginx-ingress-controller), you'll see the external IP displayed:

demo@shredder:~$ kubectl get services -n nginx-ingress-controller
NAME                                       TYPE           CLUSTER-IP       EXTERNAL-IP      PORT(S)                      AGE
nginx-ingress-controller                   LoadBalancer   10.152.183.162   172.168.209.1    80:30756/TCP,443:30462/TCP   24h
nginx-ingress-controller-default-backend   ClusterIP      10.152.183.200   <none>           80/TCP                       24h
demo@shredder:~$

Where does the external IP come from?

If you're using k3s's load balancer, the external IP will likely be the IP of the the nodes running k3s. If you're using MetalLB, the external IP should come from the list of addresses in the pool you allocated.

Pointing your web browser to the external IP displayed should result in the default backend page (or an nginx-branded 404). Congratulations, you have external access to the ingress controller! 🥳

Test Ingress

Still, you didn't deploy an ingress controller to look at 404 pages! If you used my template repository to start off your flux deployment strategy, then the podinfo helm chart has already been deployed. By default, the podinfo configmap doesn't deploy an Ingress, but you can change this using the magic of GitOps... 🪄

Edit your podinfo helmrelease configmap (/podinfo/configmap-podinfo-helm-chart-value-overrides.yaml), and change ingress.enabled to true, and set the host name to match your local domain name (already configured using External DNS):

    ingress:
      enabled: false
      className: ""
      annotations: {}
        # kubernetes.io/ingress.class: nginx
        # kubernetes.io/tls-acme: "true"
      hosts:
        - host: podinfo.local

To:

    ingress:
      enabled: false
      className: ""
      annotations: {}
        # kubernetes.io/ingress.class: nginx
        # kubernetes.io/tls-acme: "true"
      hosts:
        - host: podinfo.<your domain name>

Commit your changes, wait for a reconciliation, and run kubectl get ingress -n podinfo. You should see an ingress created matching the host defined above, and the ADDRESS value should match the service address of the nginx-ingress-controller service.

root@cn1:~# kubectl get ingress -A
NAMESPACE               NAME                                 CLASS    HOSTS                                  ADDRESS        PORTS     AGE
podinfo                 podinfo                              <none>   podinfo.example.com                    172.168.209.1   80, 443   91d

Why is there no class value?

You don't have to define an ingress class if you only have one class of ingress, since typically your ingress controller will assume the default class. When you run multiple ingress controllers (say, nginx and traeifk, or multiple nginx instances with different access controls) then classes become more important.

Now assuming your DNS is correct, you should be able to point your browser to the hostname you chose, and see the beautiful podinfo page! 🥳🥳

Test SSL

Ha, but we're not done yet! We have exposed a service via our load balancer, we've exposed a route to a service via an Ingress, but let's get rid of that nasty "insecure" message in the browser when using HTTPS...

Since you setup SSL certificates, including secret-replicator, you should end up with a letsencrypt-wildcard-cert secret in every namespace, including podinfo.

So once again, alter the podinfo ConfigMap to change this:

      tls: []
      #  - secretName: chart-example-tls
      #    hosts:
      #      - chart-example.local

To this:

      tls:
       - secretName: letsencrypt-wildcard-cert
         hosts:
           - podinfo.<your domain name>

Commit your changes, wait for the reconciliation, and the next time you point your browser at your ingress, you should get a beautiful, valid, officially-signed SSL certificate1! 🥳🥳🥳

Troubleshooting

Are things not working as expected? Watch the nginx-ingress-controller's logs with kubectl logs -n nginx-ingress-controller -l app.kubernetes.io/name=nginx-ingress-controller -f.

Chef's notes 📓

  1. The beauty of this design is that the same process will now work for any other application you deploy, without any additional manual effort for DNS or SSL setup! ↩

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