A brief and small demo of Knative - the Kubernetes-based platform to build, deploy, and manage modern serverless workloads

The instructions on how to install KNative are available in the official Knative repo.

Alternatively, you may install Knative on GKE (Google Kubernetes Engine) just running the install-knative-gke.sh script, available in this repo, or just copy and paste the following to your shell (use carefully!):

curl -sSL https://git.io/fpVaH | bash

PS. This script will create a 3-node Kubernetes cluster on GKE with the n1-standard-4 machine type. Please, check the GKE documentation to find more details (as well as pricing) about the machine types.

• Create a new file named helloworld.go and paste the following code. This code creates a basic web server which listens on port 8080:

  package main
  
  import (
  	"flag"
  	"fmt"
  	"log"
  	"net/http"
  	"os"
  )
  
  func handler(w http.ResponseWriter, r *http.Request) {
  	log.Print("Hello world received a request.")
  	target := os.Getenv("TARGET")
  	if target == "" {
  		target = "World"
  	}
  	fmt.Fprintf(w, "Hello %s!\n", target)
  }
  
  func main() {
  	flag.Parse()
  	log.Print("Hello world sample started.")
  
  	http.HandleFunc("/", handler)
  	http.ListenAndServe(":8080", nil)
  }

  • Create a Dockerfile with the following contents:

  # Start from a Debian image with the latest version of Go installed
  # and a workspace (GOPATH) configured at /go.
  FROM golang
  
  # Copy the local package files to the container's workspace.
  ADD . /go/src/github.com/knative/docs/helloworld
  
  # Build the helloworld command inside the container.
  # (You may fetch or manage dependencies here,
  # either manually or with a tool like "godep".)
  RUN go install github.com/knative/docs/helloworld
  
  # Run the helloworld command by default when the container starts.
  ENTRYPOINT /go/bin/helloworld
  
  # Document that the service listens on port 8080.
  EXPOSE 8080
  

• Create a service.yaml file with the following contents:

apiVersion: serving.knative.dev/v1alpha1 # Current version of Knative
kind: Service
metadata:
  name: helloworld-go # The name of the app
  namespace: default # The namespace the app will use
spec:
  runLatest:
    configuration:
      revisionTemplate:
        spec:
          container:
            image: gcr.io/${KNATIVE_PROJECT}/helloworld-go # The URL to the image of the app
            env:
            - name: TARGET # The environment variable printed out by the sample app
              value: "Go Sample v1"

• Build the container image locally:

docker build -t gcr.io/${KNATIVE_PROJECT}/helloworld-go .

• Push it to the remote registry:

docker push gcr.io/${KNATIVE_PROJECT}/helloworld-go

• Apply the configuration

  kubectl apply --filename service.yaml
  

• Find the IP address of your service (and export it as a system variable):

  kubectl get svc knative-ingressgateway --namespace istio-system
  export IP_ADDRESS=$(kubectl get svc knative-ingressgateway --namespace istio-system --output 'jsonpath={.status.loadBalancer.ingress[0].ip}')
  

• Find the URL of your service (and export it as a system variable):

  kubectl get services.serving.knative.dev helloworld-go  --output=custom-columns=NAME:.metadata.name,DOMAIN:.status.domain
  export HOST_URL=$(kubectl get services.serving.knative.dev helloworld-go  --output jsonpath='{.status.domain}')
  

• Request the app and see the results:

curl -H "Host: ${HOST_URL}" http://${IP_ADDRESS}
Hello World: Go Sample v1!

Based on the official Knative documentation, licensed under the Creative Commons Attribution 4.0 License, and code samples are licensed under the Apache 2.0 License