Deploy functions to Knative using the OpenFaaS CLI

This tutorial shows how to use the faas-cli to deploy functions to Knative.

• Install Knative on any Kubernetes following the Knative Installation Guide. This tutorial works on any architecture that Knative supports, I will use Knative on Arm, Check out my tutorial Knative on Raspberry Pi.

• Setup Docker-Desktop with experimental to enable buildx this will be used to build multi-architecture images including arm64.

• Install FaaS CLI using arkade

  arkade get faas-cli

• Create new app using one of the default template store (ie csharp, dockerfile, go, java11, java11-vert-x, node, node12, php7, python, python3, python3-debian, ruby) Or run faas-cli template store list to see a range of other templates from the community. In this example I'm using node12 and setting the flag --prefix for the container registry and namespace, in my case I am using docker.io/csantanapr

  faas-cli new --lang node12 hello --prefix docker.io/csantanapr

• Build and publish the container image leveraging docker buildx for two architectures.

  faas-cli publish -f hello.yml --platforms linux/amd64,linux/arm64

• Generate the Kubernetes Knative Custom Resource using the value serving.knative.dev/v1 for the CRD API, the defaul namespace used is openfaas-fn you can change this, I'm going to use default

  faas-cli generate --api=serving.knative.dev/v1 -f hello.yml -n default

• You can take the standard output redirect to a file, then add additional attributes to the Knative definition, by default the faas-cli generates a simple service with the container image uri that we published a previous step. This is a sample output:

  apiVersion: serving.knative.dev/v1
  kind: Service
  metadata:
    name: hello
    namespace: default
  spec:
    template:
      spec:
        containers:
        - image: docker.io/csantanapr/hello:latest

  You can pipe it to service.yaml like this

  faas-cli generate --api=serving.knative.dev/v1 -f hello.yml -n default > service.yaml

• To deploy the service to your cluster (ie. raspberry pi) configure your kubectl target context

  kubectx knative-pi

• You can edit and deploy the Knative yaml, or you can generate and apply in one step, by piping the output to kubectl

  faas-cli generate --api=serving.knative.dev/v1 -f hello.yml -n default | kubectl apply -f -

• Wait for Knative Service to be Ready

  kubectl wait ksvc hello --all --timeout=-1s --for=condition=Ready

• Get the URL of the new Service

  SERVICE_URL=$(kubectl get ksvc hello -o jsonpath='{.status.url}')
  echo $SERVICE_URL

• Test the App

  curl -d 'Hello World' -H "Content-Type: text/plain" $SERVICE_URL

• The output is the return value from the source code handler.js now you can go ahead and change the code based on nodejs runtime contract, and publish a new image tag and Update the tag in hello.yml

  {"status":"Received input: Hello World"}

• You can also try JSON

  curl -d '{"msg":"Hello World"}' -H "Content-Type: application/json" $SERVICE_URL

  The output

  {"status":"Received input: {\"msg\":\"Hello World\"}"}