Autoscaling

Knative Serving provides automatic scaling, also known as autoscaling. This means that a Knative Service by default scales down to zero running pods when it is not in use.

List your Knative Service

Use the Knative (kn) CLI to view the URL where your Knative Service is hosted:

knkubectl

View a list of Knative Services by running the command:

  1. kn service list

Expected output

  1. NAME    URL                                                LATEST        AGE   CONDITIONS   READY
  2. 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:

  1. kubectl get ksvc

Expected output

  1. NAME    URL                                                LATESTCREATED   LATESTREADY   READY   REASON
  2. 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:

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

Expected output

  1. 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:

  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.

Observe autoscaling

Watch the pods and see how they scale to zero after traffic stops going to the URL:

  1. kubectl get pod -l serving.knative.dev/service=hello -w

Note

It may take up to 2 minutes for your pods to scale down. Pinging your service again resets this timer.

Expected output

  1. NAME                                     READY   STATUS
  2. hello-world                              2/2     Running
  3. hello-world                              2/2     Terminating
  4. hello-world                              1/2     Terminating
  5. hello-world                              0/2     Terminating

Scale up your Knative Service

Rerun the Knative Service in your browser. You can see a new pod running again:

Expected output

  1. NAME                                     READY   STATUS
  2. hello-world                              0/2     Pending
  3. hello-world                              0/2     ContainerCreating
  4. hello-world                              1/2     Running
  5. hello-world                              2/2     Running

Exit the kubectl watch command with Ctrl+c.