OpenFaas function failed to deploy with status code: 500

Question

my environment: k3d+openFaas on mac I was deploying my first python function with OpenFaas, and failed.

beatles@xxxxxMBP openfaas % faas-cli deploy -f ./cpu.yml          
Deploying: float-operation.
WARNING! You are not using an encrypted connection to the gateway, consider using HTTPS.

Is OpenFaaS deployed? Do you need to specify the --gateway flag?
Put "http://gateway.openfaas:8080/system/functions": dial tcp: lookup gateway.openfaas: no such host

Function 'float-operation' failed to deploy with status code: 500

I suppose it might be a gateway problem, but I don't know how it actually works.

I already check official troubleshooting and Alex's tutorial Vedio, I saw he used -g http://xxxxx, but I don't know what it is?

beatles@xxxxMBP openfaas % kubectl get service -n openfaas

NAME               TYPE        CLUSTER-IP      EXTERNAL-IP   PORT(S)          AGE
alertmanager       ClusterIP   10.43.116.214   <none>        9093/TCP         15d
gateway-external   NodePort    10.43.191.86    <none>        8080:31112/TCP   15d
gateway            ClusterIP   10.43.216.241   <none>        8080/TCP         15d
nats               ClusterIP   10.43.163.95    <none>        4222/TCP         15d
prometheus         ClusterIP   10.43.131.242   <none>        9090/TCP         15d