Imran Hussain

Imran Hussain

Random Musings...

© 2020

Adventures with On-prem Kubernetes (Kubespray) with Ingress (NGINX Ingress) and a Load Balancer (MetalLB)

Setting up a on-prem Kubernetes cluster with all the bells and whistles

Preface

I honestly wish I’d found this blog before I started my journey, it’s a little old but still basically holds ups in 2020.

Part 2 is a little out of date with regards to how to deploy the ingress and load balancer components, so I’ll cover off what I assume is the way to do it these days.

Kubernetes via Kubespray

To be frank; the Kubespray documentation isn’t great at explaining everything, it very much expects you to know a fair amount about kubernetes before you use it, which is fair enough.

I’ll list some of the changes I made along the way

group_vars/all/all.yml

kubeconfig_localhost: true # Saves the kubectl conf file to artifacts/admin.conf

etcd_kubeadm_enabled: true # Decided to enable this new experimental feature

# Don't rely on a external loadbalancer
# Install one on every worker node
# I'm sure this could be replaced down the line with MetalLB and NGINX Ingress...
loadbalancer_apiserver_localhost: true
loadbalancer_apiserver_type: nginx

cert_management: script # Generate certs for us

group_vars/k8s-cluster/k8s-cluster.yml

kube_proxy_strict_arp: true #Needed for MetalLB

dns_min_replicas: 3 #I had three masters so went with one dns replica for master

kubeadm_control_plane: true # Decided to enable this new experimental feature

group_vars/k8s-cluster/addons.yml

# Enable the deployment of NGINX Ingress
# But don't enable the HostNetwork stuff as we'll be using MetalLB as LoadBalancer
ingress_nginx_enabled: true
ingress_nginx_host_network: false


# MetalLB Config
# See https://github.com/kubernetes-sigs/kubespray/blob/master/contrib/metallb
metallb:
  ip_range:
    - "10.0.70.100-10.0.70.132" # Choose IP range MetalLB can give out on the L2 network segment
  protocol: "layer2"
  limits:
    cpu: "100m"
    memory: "100Mi"
  port: "7472"
  version: v0.7.3

Once deployed you’ll have a working Kubernetes cluster (hopefully).

Load Balancer via MetalLB

Super easy to deploy as you did the config in group_vars/k8s-cluster/addons.yml, just follow the readme in the kubespray docs.

Ingress via NGINX Ingress

This one is mostly already done via kubespray apart from the service of type: LoadBalancer.

We want to use a similar service definition from the cloud config rather than the baremetal one because the baremetal one uses NodePort instead of LoadBalancer which we just setup via MetalLB.

We also have to modify the selector to match what kubespray has deployed.

Create and deploy a file called nginx-ingress-service.yaml with the contents:

# Source: ingress-nginx/templates/controller-service-webhook.yaml
apiVersion: v1
kind: Service
metadata:
  labels:
    app.kubernetes.io/name: ingress-nginx
    app.kubernetes.io/instance: ingress-nginx
    app.kubernetes.io/component: controller
  name: ingress-nginx-controller-admission
  namespace: ingress-nginx
spec:
  type: ClusterIP
  ports:
    - name: https-webhook
      port: 443
      targetPort: webhook
  selector:
    app.kubernetes.io/name: ingress-nginx
    app.kubernetes.io/part-of: ingress-nginx
---
# Source: ingress-nginx/templates/controller-service.yaml
apiVersion: v1
kind: Service
metadata:
  labels:
    app.kubernetes.io/name: ingress-nginx
    app.kubernetes.io/instance: ingress-nginx
    app.kubernetes.io/component: controller
  name: ingress-nginx-controller
  namespace: ingress-nginx
spec:
  type: LoadBalancer
  externalTrafficPolicy: Cluster
  ports:
    - name: http
      port: 80
      protocol: TCP
      targetPort: http
    - name: https
      port: 443
      protocol: TCP
      targetPort: https
  selector:
    app.kubernetes.io/name: ingress-nginx
    app.kubernetes.io/part-of: ingress-nginx

You should now have a ingress service with a EXTERNAL-IP that was obtained from our load balancer, verify this by making sure the IP is in the range that you specified MetalLB config when looking at services in the ingress-nginx namespace.

Test the setup

Lets deploy a simple container that says hello world over http on port 3000.

We’ll make a deployment, a service using ClusterIP using port 8008 and then setup an ingress to point to it on the path /test.

hello-world-d_s_i.yaml

apiVersion: apps/v1
kind: Deployment
metadata:
  name: hello-world-deployment
spec:
  selector:
    matchLabels:
      app: hello-world-debug
  replicas: 3
  template:
    metadata:
      labels:
        app: hello-world-debug
    spec:
      containers:
      - name: hello-world-debug
        image: "imranh2/hello-world-debug"
        env:
        - name: "PORT"
          value: "3000"

---
apiVersion: v1
kind: Service
metadata:
  name: hello-world-service
spec:
  type: ClusterIP
  selector:
    app: hello-world-debug
  ports:
  - protocol: TCP
    port: 8008
    targetPort: 3000

---
apiVersion: extensions/v1beta1
kind: Ingress
metadata:
  name: hello-world-ingress
  annotations: 
     nginx.ingress.kubernetes.io/rewrite-target: /
     nginx.ingress.kubernetes.io/ssl-redirect: "false"
spec:
  rules:
  - http:
      paths:
      - path: /test
        backend:
          serviceName: hello-world-service
          servicePort: 8008

curl http://$(kubectl get services ingress-nginx-controller -n ingress-nginx --output jsonpath='{.status.loadBalancer.ingress[0].ip}')/test

You should see the container output :)

Closing Thoughts

  • Source IP to containers - The direct TCP/IP connection you see is the Pod IP of a Ingress Controller, as that’s where the external connection is being terminated. For HTTP(S) there’s X-FORWARDED-FOR. Setting externalTrafficPolicy: Cluster to Local and using BGP instead of layer2 to announce will let you see the real IP for non-HTTP application allegadly.

  • Kubernetes API EXTERNAL-IP - As we now have a load balancer we could give the kubernetes API itself a EXTERNAL-IP. Then possibly reconfigure the entire cluster to use that VIP via the loadbalancer_apiserver config options, also editing supplementary_addresses_in_ssl_keys to include the VIP and domain. How sensible it is to have your API LB as part of your cluster is left up to you to decide….

I think I had some more thoughts but they’ve escaped me for now…