Scale to Zero¶
OpenFaaS Pro offers an additional component that can be used to scale idle functions to zero replicas. When scaled to zero, functions do not consume CPU or memory, and are then scaled back to the minimum desired amount of replicas upon first use.
Scaling to zero can save money by make your resources go further:
- Fewer nodes are required in your cluster
- If you have a limited pool of nodes, you can make more efficient use of them
Scaling to zero can also increase security:
- If any of your functions have a vulnerability, the attack surface is reduced to only the time they are running
- Each time the function runs, it may be run on a different node with a freshly pulled image
Scale to Zero is enabled automatically when you install OpenFaaS Pro with helm and set
autoscaler.enabled: true. You can see a sample configuration for OpenFaaS Pro here.
If you worked with an older version of OpenFaaS Pro, then you'll remember faas-idler. It has now been replaced by the OpenFaaS Pro autoscaler which performs both Horizontal Scaling of functions between their minimum and maximum replica count, and down to zero.
Check the autoscaler is deployed¶
First of all, if you have access to "kubectl", check that the autoscaler is deployed and running:
# Check the deployment is present kubectl get deploy -n openfaas autoscaler -o wide # Start watching its logs kubectl logs -n openfaas deploy/autoscaler \ --since 30s -f
Configure a function to scale to zero¶
By default, functions do not scale to zero, even when the OpenFaaS Pro autoscaler is installed. This is by design, and means that you need to opt-in each of your functions to scale down.
This is achieved through adding a label to the stack.yml file:
false- default is false
com.openfaas.scale.zero-duration- the time in a Go duration where there are no requests incoming before scaling a function down i.e.
Try out an example function¶
The ttl.sh registry is a free service that can be used to publish a container image without needing to log into a registry.
Create a new function using the
export OPENFAAS_PREFIX=ttl.sh/daily-job:1h faas-cli new --lang go daily-job
Now add the labels from above, we'll use a 15 minute timeout.
You can specify a Go duration such as
1h. It's recommended that scale down time is set to at least 5-10 minutes to prevent any thrashing that may occur if the traffic to a function is sporadic.
version: 1.0 provider: name: openfaas gateway: http://127.0.0.1:8080 functions: daily-job: lang: go handler: ./daily-job image: ttl.sh/daily-job:1h labels: com.openfaas.scale.zero: true com.openfaas.scale.zero-duration: 15m
Then build and deploy the function to your OpenFaaS Pro cluster:
# Build, push and deploy the function: faas-cli up -f daily-job.yml # Invoke the function: echo | faas-cli invoke daily-job
Once you have deployed and invoked your function, you should see it start to appear in the logs of the autoscaler:
kubectl logs -n openfaas deploy/autoscaler \ --since 30s -f
Open another terminal to monitor the replicas of your function:
kubectl get -n openfaas-fn \ deploy/daily-job -w
After the chosen scale to zero period, you will see its replicas scale to zero.
Then, you can invoke the function and you'll see the function scale up and get invoked again:
echo | faas-cli invoke daily-job
If you're interested in seeing the various Kubernetes events involved in scaling from zero, you can run:
kubectl get event -n openfaas-fn -w
You can also deploy a test function from the OpenFaaS Store, but bear in mind that they are not necessarily suitable for load testing:
faas-cli store deploy nodeinfo \ --label com.openfaas.scale.zero=true \ --label com.openfaas.scale.zero-duration=15m
To disable scale to zero for any function, set
false, or don't add the label at all.
You can learn more about OpenFaaS auto-scaling here: autoscaling
The time taken to scale up a function and have it ready to serve traffic is called a "cold-start". To learn what a cold-start is, and why they are present in Kubernetes, and how to minimise them in OpenFaaS, read: Dude where's my coldstart?
Cold-starts can be tuned through the OpenFaaS Helm chart: Tuning function cold-starts
Would you like a demo?¶
Feel free to reach out to us for a demo or to ask any questions you may have.