Network setting
K3s will come with pretty much everything pre-configured like traefik.
More info about traefik: https://doc.traefik.io/traefik/
However, I would like to have LoadBalancer, and in essence to be able to give services (pods) an external IP, just like my Kubernetes nodes, not from internal Kubernetes ranges. Normally, this is an external component, and your cloud provider should somehow magically give that to you, but since we are our own cloud provider, and we are trying to keep everything in one cluster... in short MetalLB is the answer.
What is MetalLB
Deployment
This is a two-step process: we deploy MetalLB load balancer, and then push configuration to it, and tell it what range of IPs to use.
Apply the following: first we will create a namespace called metallb-system, and second we will deploy MetalLB into it.
Note
Look here https://metallb.universe.tf/installation/ for the most up to date version of metallb links.
kubectl apply -f https://raw.githubusercontent.com/metallb/metallb/v0.9.5/manifests/namespace.yaml
kubectl apply -f https://raw.githubusercontent.com/metallb/metallb/v0.9.5/manifests/metallb.yaml
Note
I prefer to store configuration files in folders named after components we deploy to cluster so that I can easily delete the service later without looking at links pointing to the Internet. So, you can just create folder MetalLB, and download the yaml file into it for later use.
We need to create a secret key for the speakers (the MetalLB pods) to encrypt speaker communications:
kubectl create secret generic -n metallb-system memberlist --from-literal=secretkey="$(openssl rand -base64 128)"
Configuration
Next, create config.yaml in your MetalLB folder; here we are going to tell MetalLB what IPs to use:
apiVersion: v1
kind: ConfigMap
metadata:
namespace: metallb-system
name: config
data:
config: |
address-pools:
- name: default
protocol: layer2
addresses:
- 192.168.0.230-192.168.0.250
As you can see, I specified a range from 192.168.0.230 to 192.168.0.250. That will give me 20 "external" IPs to work with for now.
Apply the config:
kubectl apply -f config.yaml
Check
Check if everything deployed OK
root@control01:~# kubectl get pods -n metallb-system
NAME READY STATUS RESTARTS AGE
controller-65db86ddc6-7h59v 1/1 Running 0 6d5h
speaker-6vjzn 1/1 Running 0 6d5h
speaker-b25rk 1/1 Running 0 6d5h
speaker-dw2pv 1/1 Running 0 6d5h
speaker-gdjzr 1/1 Running 0 6d5h
speaker-hc72j 1/1 Running 0 6d5h
speaker-k9nzq 1/1 Running 0 6d5h
speaker-mfmkq 1/1 Running 0 6d5h
speaker-qzvvz 1/1 Running 0 6d5h
speaker-z6dk6 1/1 Running 0 6d5h
You should have as many speaker-xxxx as you have nodes in the cluster, since they run one per node.
Now services that use LoadBalancer should have an external IP assigned to them.
For example:
root@control01:~# kubectl get svc --all-namespaces
NAMESPACE NAME TYPE CLUSTER-IP EXTERNAL-IP PORT(S) AGE
default kubernetes ClusterIP 10.43.0.1 <none> 443/TCP 8d
kube-system kube-dns ClusterIP 10.43.0.10 <none> 53/UDP,53/TCP,9153/TCP 8d
kube-system metrics-server ClusterIP 10.43.246.167 <none> 443/TCP 8d
kube-system traefik LoadBalancer 10.43.61.64 192.168.0.230 80:31712/TCP,443:31124/TCP 8d
kube-system traefik-prometheus ClusterIP 10.43.178.172 <none> 9100/TCP 8d
kubernetes-dashboard dashboard-metrics-scraper ClusterIP 10.43.147.66 <none> 8000/TCP 8d
kubernetes-dashboard kubernetes-dashboard ClusterIP 10.43.151.250 <none> 443/TCP 8d
longhorn-system csi-attacher ClusterIP 10.43.125.73 <none> 12345/TCP 8d
longhorn-system csi-provisioner ClusterIP 10.43.118.73 <none> 12345/TCP 8d
longhorn-system csi-resizer ClusterIP 10.43.245.224 <none> 12345/TCP 8d
longhorn-system csi-snapshotter ClusterIP 10.43.230.3 <none> 12345/TCP 8d
longhorn-system longhorn-backend ClusterIP 10.43.118.82 <none> 9500/TCP 8d
longhorn-system longhorn-frontend ClusterIP 10.43.204.227 <none> 80/TCP 8d
openfaas alertmanager ClusterIP 10.43.79.30 <none> 9093/TCP 6d6h
openfaas basic-auth-plugin ClusterIP 10.43.163.133 <none> 8080/TCP 6d6h
openfaas gateway ClusterIP 10.43.187.155 <none> 8080/TCP 6d6h
openfaas gateway-external NodePort 10.43.71.53 <none> 8080:31112/TCP 6d6h
openfaas nats ClusterIP 10.43.123.99 <none> 4222/TCP 6d6h
openfaas prometheus ClusterIP 10.43.78.247 <none> 9090/TCP 6d6h
Look how traefik automatically got an IP from the external range. In the end, this is what you would want: Not to point to a single node IP and be redirected based on DNS, which would stop working the moment the node with that IP died. This way, we make the external IP node independent. Now, you can point DNS to that IP and be sure it will be routed correctly.
Note
This is how I prefer my network settings, and makes most sense to me when creating external services. I'm sure there are like a hundred different methods using external load balancers, Nginx ingress (basically reverse proxy) and who knows what in production, but hey, there is no official one standardized setting for Kubernetes (which can be such a pain sometimes) so who’s to say this is not OK? 🙂