Deploying your first Knative Service

In this tutorial, you will deploy a "Hello world" service.

Since our "Hello world" Service is being deployed as a Knative Service, not a Kubernetes Service, it gets some super powers out of the box .

Knative Service: "Hello world!"

First, deploy the Knative Service. This service accepts the environment variable, TARGET, and prints Hello ${TARGET}!.

knYAML

Deploy the Service by running the command:

kn service create hello \
--image gcr.io/knative-samples/helloworld-go \
--port 8080 \
--env TARGET=World

Expected output

Service hello created to latest revision 'hello-world' is available at URL:
http://hello.default.${LOADBALANCER_IP}.sslip.io

The value of ${LOADBALANCER_IP} above depends on your type of cluster, for kind it will be 127.0.0.1 for minikube depends on the local tunnel.

1. Copy the following YAML into a file named hello.yaml:

   apiVersion: serving.knative.dev/v1
   kind: Service
   metadata:
     name: hello
   spec:
     template:
       spec:
         containers:
           - image: gcr.io/knative-samples/helloworld-go
             ports:
               - containerPort: 8080
             env:
               - name: TARGET
                 value: "World"
   

2. Deploy the Knative Service by running the command:

   kubectl apply -f hello.yaml
   

   Expected output

   service.serving.knative.dev/hello created
   

List your Knative Service

To see the URL where your Knative Service is hosted, leverage the kn CLI:

knkubectl

View a list of Knative services by running the command:

kn service list

Expected output

NAME    URL                                                LATEST        AGE   CONDITIONS   READY
hello   http://hello.default.${LOADBALANCER_IP}.sslip.io   hello-00001   13s   3 OK / 3     True

View a list of Knative services by running the command:

kubectl get ksvc

Expected output

NAME    URL                                                LATESTCREATED   LATESTREADY   READY   REASON
hello   http://hello.default.${LOADBALANCER_IP}.sslip.io   hello-00001     hello-00001   True

Access your Knative Service

Access your Knative Service by opening the previous URL in your browser or by running the command:

echo "Accessing URL $(kn service describe hello -o url)"
curl "$(kn service describe hello -o url)"

Expected output

Hello World!

Are you seeing curl: (6) Could not resolve host: hello.default.${LOADBALANCER_IP}.sslip.io?

In some cases your DNS server may be set up not to resolve *.sslip.io addresses. If you encounter this problem, it can be fixed by using a different nameserver to resolve these addresses.

The exact steps will differ according to your distribution. For example, with Ubuntu derived systems which use systemd-resolved, you can add the following entry to the /etc/systemd/resolved.conf:

[Resolve]
DNS=8.8.8.8
Domains=~sslip.io.

Then simply restart the service with sudo service systemd-resolved restart.

For MacOS users, you can add the DNS and domain using the network settings as explained here.

Congratulations , you've just created your first Knative Service. Up next, Autoscaling!