Using KEDA with Promethues scaler

 

In this post we will show a simple usage of KEDA with prometheus scaler to set the replicas number of a deployment.

KEDA is an event driven autoscaler, it wraps up the kubernetes horizontal pod autoscaler and simplify autoscaling while enabling scaler by a huge collection of scale metrics sources.

Deploy KEDA

Deploying KEDA is done by using helm chart:

helm repo add kedacore https://kedacore.github.io/charts
helm repo update
helm install keda kedacore/keda --namespace keda --create-namespace

Deploy a Scaledobject

A scaledobject is a configuration of the required auto scaling. We deploy the following scaledobject:

apiVersion: keda.sh/v1alpha1
kind: ScaledObject
metadata:
  name: my-scaledobject
  namespace: default
spec:
  minReplicaCount: 1
  maxReplicaCount: 5
  pollingInterval: 5
  cooldownPeriod: 30
  scaleTargetRef:
    name: my-deployment
    kind: Deployment
    apiVersion: apps/v1
  triggers:
    - type: prometheus
      metadata:
        serverAddress: http://prometheus-service.default:80
        threshold: '100'
        query: sum (rate(handled_items[1m]))

We specify the min and max replicas, as well as the polling interval, and the cooldown internal.

The scaled object target is a deployment.

The metric source is prometheus, whose service address must be supplied. The scale is done using a promethues metric value. In this example, we set the threshold to 100, which means that above an average of 100 per pod, KEDA will scale up the replicas amount.