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Getting Started with Knative App Deployment

This guide shows you how to deploy an app using Knative, then interact with it using cURL requests.

Before you begin

You need:

  • A Kubernetes cluster with Knative installed.
  • An image of the app that you'd like to deploy available on a container registry. The image of the sample app used in this guide is available on Google Container Registry.

Sample application

This guide uses the Hello World sample app in Go to demonstrate the basic workflow for deploying an app, but these steps can be adapted for your own application if you have an image of it available on Docker Hub, Google Container Registry, or another container image registry.

The Hello World sample app reads in an env variable, TARGET, from the configuration .yaml file, then prints "Hello World: ${TARGET}!". If TARGET isn't defined, it will print "NOT SPECIFIED".

Configuring your deployment

To deploy an app using Knative, you need a configuration .yaml file that defines a Service. For more information about the Service object, see the Resource Types documentation.

This configuration file specifies metadata about the application, points to the hosted image of the app for deployment, and allows the deployment to be configured. For more information about what configuration options are available, see the Serving spec documentation.

Create a new file named service.yaml, then copy and paste the following content into it:

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-samples/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"

If you want to deploy the sample app, leave the config file as-is. If you're deploying an image of your own app, update the name of the app and the URL of the image accordingly.

Deploying your app

From the directory where the new service.yaml file was created, apply the configuration:

kubectl apply --filename service.yaml

Now that your service is created, Knative will perform the following steps:

  • Create a new immutable revision for this version of the app.
  • Perform network programming to create a route, ingress, service, and load balancer for your app.
  • Automatically scale your pods up and down based on traffic, including to zero active pods.

Interacting with your app

To see if your app has been deployed succesfully, you need the host URL and IP address created by Knative.

Note: If your cluster is new, it can take some time before the service is asssigned an external IP address.

  1. To find the IP address for your service, enter:

     kubectl get svc knative-ingressgateway --namespace istio-system

 NAME                     TYPE           CLUSTER-IP     EXTERNAL-IP      PORT(S)                                      AGE
 knative-ingressgateway   LoadBalancer   10.23.247.74   35.203.155.229   80:32380/TCP,443:32390/TCP,32400:32400/TCP   2d

    Take note of the EXTERNAL-IP address.

    You can also export the IP address as a variable with the following command:

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

    Note: if you use minikube or a baremetal cluster that has no external load balancer, the EXTERNAL-IP field is shown as <pending>. You need to use NodeIP and NodePort to interact your app instead. To get your app's NodeIP and NodePort, enter the following command:

    export IP_ADDRESS=$(kubectl get node  --output 'jsonpath={.items[0].status.addresses[0].address}'):$(kubectl get svc knative-ingressgateway --namespace istio-system   --output 'jsonpath={.spec.ports[?(@.port==80)].nodePort}')

  2. To find the host URL for your service, enter:

    kubectl get services.serving.knative.dev helloworld-go  --output=custom-columns=NAME:.metadata.name,DOMAIN:.status.domain
NAME                DOMAIN
helloworld-go       helloworld-go.default.example.com

    You can also export the host URL as a variable using the following command:

    export HOST_URL=$(kubectl get services.serving.knative.dev helloworld-go  --output jsonpath='{.status.domain}')

    If you changed the name from helloworld-go to something else when creating the .yaml file, replace helloworld-go in the above commands with the name you entered.

  3. Now you can make a request to your app and see the results. Replace IP_ADDRESS with the EXTERNAL-IP you wrote down, and replace helloworld-go.default.example.com with the domain returned in the previous step.

    curl -H "Host: helloworld-go.default.example.com" http://IP_ADDRESS
Hello World: Go Sample v1!

    If you exported the host URL And IP address as variables in the previous steps, you can use those variables to simplify your cURL request:

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

    If you deployed your own app, you might want to customize this cURL request to interact with your application.

    It can take a few seconds for Knative to scale up your application and return a response.

You've successfully deployed your first application using Knative!

Cleaning up

To remove the sample app from your cluster, delete the service record:

kubectl delete --filename service.yaml

Except as otherwise noted, the content of this page is licensed under the Creative Commons Attribution 4.0 License, and code samples are licensed under the Apache 2.0 License.