Little helper to run CNCF's k3s in Docker
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k3d/docs/usage/exposing_services.md

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# Exposing Services
## 1. via Ingress (recommended)
In this example, we will deploy a simple nginx webserver deployment and make it accessible via ingress.
Therefore, we have to create the cluster in a way, that the internal port 80 (where the `traefik` ingress controller is listening on) is exposed on the host system.
1. Create a cluster, mapping the ingress port 80 to localhost:8081
`#!bash k3d cluster create --api-port 6550 -p "8081:80@loadbalancer" --agents 2`
!!! info "Good to know"
- `--api-port 6550` is not required for the example to work.
It's used to have `k3s`'s API-Server listening on port 6550 with that port mapped to the host system.
- the port-mapping construct `8081:80@loadbalancer` means:
"map port `8081` from the host to port `80` on the container which matches the nodefilter `loadbalancer`"
- the `loadbalancer` nodefilter matches only the `serverlb` that's deployed in front of a cluster's server nodes
- all ports exposed on the `serverlb` will be proxied to the same ports on all server nodes in the cluster
2. Get the kubeconfig file (redundant, as `k3d cluster create` already merges it into your default kubeconfig file)
`#!bash export KUBECONFIG="$(k3d kubeconfig write k3s-default)"`
3. Create a nginx deployment
`#!bash kubectl create deployment nginx --image=nginx`
4. Create a ClusterIP service for it
`#!bash kubectl create service clusterip nginx --tcp=80:80`
5. Create an ingress object for it by copying the following manifest to a file and applying with `#!bash kubectl apply -f thatfile.yaml`
**Note**: `k3s` deploys [`traefik`](https://github.com/containous/traefik) as the default ingress controller
```YAML
# apiVersion: networking.k8s.io/v1beta1 # for k3s < v1.19
apiVersion: networking.k8s.io/v1
kind: Ingress
metadata:
name: nginx
annotations:
ingress.kubernetes.io/ssl-redirect: "false"
spec:
rules:
- http:
paths:
- path: /
pathType: Prefix
backend:
service:
name: nginx
port:
number: 80
```
6. Curl it via localhost
`#!bash curl localhost:8081/`
## 2. via NodePort
1. Create a cluster, mapping the port `30080` from `agent-0` to `localhost:8082`
`#!bash k3d cluster create mycluster -p "8082:30080@agent:0" --agents 2`
- **Note 1**: Kubernetes' default NodePort range is [`30000-32767`](https://kubernetes.io/docs/concepts/services-networking/service/#nodeport)
- **Note 2**: You may as well expose the whole NodePort range from the very beginning, e.g. via `k3d cluster create mycluster --agents 3 -p "30000-32767:30000-32767@server:0"` (See [this video from @portainer](https://www.youtube.com/watch?v=5HaU6338lAk))
- **Warning**: Docker creates iptable entries and a new proxy process per port-mapping, so this may take a very long time or even freeze your system!
... (Steps 2 and 3 like above) ...
1. Create a NodePort service for it by copying the following manifest to a file and applying it with `#!bash kubectl apply -f`
```YAML
apiVersion: v1
kind: Service
metadata:
labels:
app: nginx
name: nginx
spec:
ports:
- name: 80-80
nodePort: 30080
port: 80
protocol: TCP
targetPort: 80
selector:
app: nginx
type: NodePort
```
2. Curl it via localhost
`#!bash curl localhost:8082/`