Deploying your first Knative Service

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

This service will accept an environment variable, TARGET, and print “Hello ${TARGET}!.”

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!”

knYAML

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

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

apiVersion: serving.knative.dev/v1
kind: Service
metadata:
  name: hello
spec:
  template:
    metadata:
      # This is the name of our new "Revision," it must follow the convention {service-name}-{revision-name}
      name: hello-world
    spec:
      containers:
        - image: gcr.io/knative-samples/helloworld-go
          ports:
            - containerPort: 8080
          env:
            - name: TARGET
              value: "World"

Once you’ve created your YAML file (named something like “hello.yaml”):

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:

service.serving.knative.dev/hello created

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

kn service list

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:

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

Expected output:

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:

[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!