ok-server/README.md

# Connectivity Test Server

A simple HTTP server for connectivity testing. It can be run from the command line or in a container.

The Python version relies only on Python's standard library, so it should work in any environment with Python installed. The Node.js version also relies only on the standard library, so it should work in any environment with Node.js installed. The Go version also relies only on the standard library, so it should work in any environment with Go installed.

It displays a simple HTML or plain-text page with the client's IP address and any detected `X-*` headers.

## Disclaimer

The **ok-server** scripts were generated using AI under human supervision. The owner of the repository is not responsible for any issues that may arise from using the AI-generated code.

## Usage

### Command Line

To run the server from the command line:

```bash
python3 ok-server.py
python3 ok-server.py --look basic
python3 ok-server.py --bind 127.0.0.1 --port 8080 --look tailwind
python3 ok-server.py --pem /path/to/bundle.pem
python3 ok-server.py --pem /path/to/bundle.pem --tls-port 9443
```

`--look` accepts `basic`, `nice`, `bootstrap`, or `tailwind`.
You can override the look per request with the `look` query parameter, for example:
`http://localhost:8080/?look=tailwind`

`--pem` accepts a path to a PEM file containing the certificate chain and private key.
When provided, the server listens on both HTTP (`--port`, default 8080) and HTTPS (`--tls-port`, default 8443).

```bash
node ok-server.mjs
node ok-server.mjs --look basic
node ok-server.mjs --bind 127.0.0.1 --port 8080 --look tailwind
node ok-server.mjs --pem /path/to/bundle.pem
node ok-server.mjs --pem /path/to/bundle.pem --tls-port 9443
```

```bash
go run ok-server.go
go run ok-server.go --look basic
go run ok-server.go --bind 127.0.0.1 --port 8080 --look tailwind
go run ok-server.go --pem /path/to/bundle.pem
go run ok-server.go --pem /path/to/bundle.pem --tls-port 9443
```

Connect to the server using a web browser or a tool like `curl`:

```bash
curl -si "http://localhost:8080"
```

### Building a Go binary

Cross-compile for any platform from any machine:

```bash
# Linux amd64
GOOS=linux   GOARCH=amd64  go build -o ok-server-linux-amd64   ok-server.go

# Linux arm64
GOOS=linux   GOARCH=arm64  go build -o ok-server-linux-arm64   ok-server.go

# macOS arm64 (Apple Silicon)
GOOS=darwin  GOARCH=arm64  go build -o ok-server-darwin-arm64  ok-server.go

# macOS amd64 (Intel)
GOOS=darwin  GOARCH=amd64  go build -o ok-server-darwin-amd64  ok-server.go

# Windows amd64
GOOS=windows GOARCH=amd64  go build -o ok-server-windows-amd64.exe ok-server.go
```

### Docker

Use the included `Dockerfile` to build and run the server in a Docker container:

```bash
docker build -t ok-server .
docker run -d --restart unless-stopped --name ok-server --cpus=1 --memory=256m -p 8080:8080 ok-server
```

This will start the server and expose it on port 8080. The container will run until stopped. You can restart it with `docker start ok-server`, or remove it with `docker rm ok-server`.

### Container CLI on a Mac

```shell
container builder stop
container builder start -c 4 -m 1G
container build -t ok-server .
container run --rm -d --name ok-server -c 1 -m 256m -p 8080:8080 ok-server
```

This will start the server and expose it on port 8080. The container will run until stopped, and will be removed when stopped. You can stop it with `container stop ok-server`.

### nerdctl with BuildKit on a k3s server

Build the image directly into the containerd instance used by k3s:

```bash
sudo nerdctl build -t ok-server .
sudo nerdctl images
```

On a single-node k3s cluster the image is now available to the kubelet without a
registry. The [k3s/deployment.yaml](k3s/deployment.yaml) Deployment references
it with `imagePullPolicy: Never`:

```bash
kubectl apply -f k3s/deployment.yaml
```

Expose the app with one of the two options below.

#### Option 1: Traefik Ingress

k3s includes the Traefik ingress controller. The ClusterIP Service and Ingress
in [k3s/expose-ingress.yaml](k3s/expose-ingress.yaml) expose the app on port 80
for the host name `ok-server.example.org`. Change the `host` value in the
Ingress to your own FQDN and point its DNS record at the node's IP address:

```bash
kubectl apply -f k3s/expose-ingress.yaml
curl -si "http://ok-server.example.org/"
```

Without a DNS record you can still test the host rule by mapping the name to
the node's IP address on the curl command line:

```bash
curl -si --resolve ok-server.example.org:80:<node-ip> "http://ok-server.example.org/"
```

By default the app sees a cluster-internal address (for example `10.42.0.1`)
instead of the real client IP, because the Traefik Service runs with
`externalTrafficPolicy: Cluster`. To preserve the client IP, set
`externalTrafficPolicy: Local` on the Traefik Service through a
`HelmChartConfig`, as in [k3s/traefik-config.yaml](k3s/traefik-config.yaml).

A cluster can hold only one `HelmChartConfig` named `traefik`, so first check
whether one already exists:

```bash
kubectl get helmchartconfig traefik -n kube-system
```

If it does not exist, apply the file as is:

```bash
kubectl apply -f k3s/traefik-config.yaml
```

If it already exists, do not apply the file, as it would replace the existing
Traefik settings. Instead, add `externalTrafficPolicy: Local` under the
`service.spec` section of the existing `valuesContent`:

```bash
kubectl edit helmchartconfig traefik -n kube-system
```

#### Option 2: ServiceLB

k3s also includes the ServiceLB load balancer. The single `LoadBalancer`
Service in [k3s/expose-servicelb.yaml](k3s/expose-servicelb.yaml) exposes the
app on port 8080 of the node's IP address, without an Ingress. The Service sets
`externalTrafficPolicy: Local` so the app sees the real client IP:

```bash
kubectl apply -f k3s/expose-servicelb.yaml
curl -si "http://<node-ip>:8080"
```

On a multi-node cluster, push the image to a registry instead, so every node can
pull it.

## License

This project is licensed under the MIT License. See the [LICENSE](LICENSE) file for details.