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:

  1. kn service create hello \
  2. --image gcr.io/knative-samples/helloworld-go \
  3. --port 8080 \
  4. --env TARGET=World \
  5. --revision-name=world

Why did I pass in revision-name?

Note the name “world” which you passed in as “revision-name,” naming your Revisions will help you to more easily identify them, but don’t worry, you’ll learn more about Revisions later.

Expected output

  1. Service hello created to latest revision 'hello-world' is available at URL:
  2. http://hello.default.127.0.0.1.sslip.io

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

    1. apiVersion: serving.knative.dev/v1
    2. kind: Service
    3. metadata:
    4.   name: hello
    5. spec:
    6.   template:
    7.     metadata:
    8.       # This is the name of our new "Revision," it must follow the convention {service-name}-{revision-name}
    9.       name: hello-world
    10.     spec:
    11.       containers:
    12.         - image: gcr.io/knative-samples/helloworld-go
    13.           ports:
    14.             - containerPort: 8080
    15.           env:
    16.             - name: TARGET
    17.               value: "World"

  2. Deploy the Knative Service by running the command:

    1. kubectl apply -f hello.yaml

    Why did I pass in the second name, hello-world?

    Note the name hello-world which you passed in under metadata in your YAML file. Naming your Revisions will help you to more easily identify them, but don’t worry if this if a bit confusing now, you’ll learn more about Revisions later.

    Expected output

    1. service.serving.knative.dev/hello created

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

    1. kn service list

    Expected output

    1. NAME    URL                                          LATEST        AGE   CONDITIONS   READY   REASON
    2. hello   http://hello.default.127.0.0.1.sslip.io   hello-world   13s   3 OK / 3     True

Ping your Knative Service

Ping your Knative Service by opening http://hello.default.127.0.0.1.sslip.io in your browser of choice or by running the command:

  1. curl http://hello.default.127.0.0.1.sslip.io

Expected output

  1. Hello World!

Are you seeing curl: (6) Could not resolve host: hello.default.127.0.0.1.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:

  1. [Resolve]
  2. DNS=8.8.8.8
  3. 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!