Scale OpenFaaS functions to zero replicas after a period of inactivity
Premise: functions (Deployments) can be scaled to 0/0 replicas from 1/1 or N/N replicas when they are not receiving traffic. Traffic is observed from Prometheus metrics collected in the OpenFaaS API Gateway.
Scaling to zero requires an "un-idler" or a blocking HTTP proxy which can reverse the process when incoming requests attempt to access a given function. This is done through the OpenFaaS API Gateway through which every incoming call passes - see Add feature: scale from zero to 1 replicas #685.
faas-idler is implemented as a controller which polls Prometheus metrics on a regular basis and tries to reconcile a desired condition - i.e. zero replicas -> scale down API call.
The build requires Docker and builds a local Docker image.
TAG=0.1.0 make build
TAG=0.1.0 make push
- Environmental variables:
gateway_url needs to be the URL of the faas-netes or faas-swarm service, which usually has no port exposed.
Try using the ClusterIP/Cluster Service instead and port 8080.
gateway_url - URL for faas-provider
prometheus_host - host for Prometheus
prometheus_port - port for Prometheus
inactivity_duration - i.e. 10m (Golang duration)
The reconcileInterval is hard-coded to run every 30s.
- Command-line args
-dry-run - don't send scaling event
How it works:
gateway_function_invocation_total is measured for activity over duration i.e. 1h of inactivity (or no HTTP requests)
You can view the logs to show reconciliation in action.
kubectl logs -n openfaas -f deploy/faas-idler