Scaling to Zero¶
Remember those super powers we talked about? One of Knative Serving's powers is built-in automatic scaling (autoscaling). This means your Knative Service only spins up your application to perform its job -- in this case, saying "Hello world!" -- if it is needed; otherwise, it will "scale to zero" by spinning down and waiting for a new request to come in.
What about scaling up to meet increased demand?
Knative Autoscaling also allows you to easily configure your service to scale up (horizontal autoscaling) to meet increased demand as well as control the number of instances that spin up using concurrency limits and other options, but that's beyond the scope of this tutorial.
Let's see this in action! We're going to peek under the hood at the Pod in Kubernetes where our Knative Service is running to watch our "Hello world!" Service scale up and down.
Run your Knative Service¶
Let's run our "Hello world!" Service just one more time. This time, try the Knative Service
http://hello.default.127.0.0.1.nip.io, or you
can use your terminal with
You can watch the pods and see how they scale to zero after traffic stops going to the URL.
kubectl get pod -l serving.knative.dev/service=hello -w
It may take up to 2 minutes for your Pods to scale down. Pinging your service again will reset this timer.
NAME READY STATUS hello-world 2/2 Running hello-world 2/2 Terminating hello-world 1/2 Terminating hello-world 0/2 Terminating
Scale up your Knative Service¶
Rerun the Knative Service in your browser http://hello.default.127.0.0.1.nip.io, and you will see a new pod running again.
NAME READY STATUS hello-world 0/2 Pending hello-world 0/2 ContainerCreating hello-world 1/2 Running hello-world 2/2 Running
Some people call this Serverless Up next, traffic splitting!
Want to go deeper on Autoscaling?
Interested in getting in the weeds with Knative Autoscaling? Check out the autoscaling documentation for concepts, samples, and more!