Trigger Specification

This specification describes the cron trigger that scales workloads in/out based on a cron Schedule.

triggers:
- type: cron
  metadata:
    # Required
    timezone: Asia/Kolkata  # The acceptable values would be a value from the IANA Time Zone Database.
    start: 0 6 * * *        # At 6:00 AM
    end: 0 20 * * *         # At 8:00 PM
    desiredReplicas: "10"

Parameter list:

• timezone - One of the acceptable values from the IANA Time Zone Database. The list of timezones can be found here.
• start - Cron expression indicating the start of the cron schedule.
• end - Cron expression indicating the end of the cron schedule.
• desiredReplicas - Number of replicas to which the resource has to be scaled between the start and end of the cron schedule.

💡 Note: start/end support “Linux format cron” (Minute Hour Dom Month Dow).

Notice: Start and end should not be same.

For example, the following schedule is not valid:

start: 0 6 * * *        # At 6:00 AM
end: 0 6 * * *          # also at 6:00 AM

How does it work?

The CRON scaler allows you to define a time range in which you want to scale your workloads out/in.

When the time window starts, it will scale from the minimum number of replicas to the desired number of replicas based on your configuration.

What the CRON scaler does not do, is scale your workloads based on a recurring schedule.

Scale to 0 during off hours

If you want to scale you deployment to 0 outside office hours / working hours, you need to set minReplicaCount: 0 in the ScaledObject, and increase the replicas during work hours. That way the Deployment will be scaled to 0 ouside that time window. By default the ScaledObject cooldownPeriod is 5 minutes, so the actual scaling down will happen 5 minutes after the cron schedule end parameter.

It’s almost always an error to try to do the other way around, i.e. set desiredReplicas: 0 in the cron trigger.

Example: scale up to 10 replicas from 6AM to 8PM and scale down to 0 replicas otherwise

apiVersion: keda.sh/v1alpha1
kind: ScaledObject
metadata:
  name: cron-scaledobject
  namespace: default
spec:
  scaleTargetRef:
    name: my-deployment
  minReplicaCount: 0
  cooldownPeriod: 300
  triggers:
  - type: cron
    metadata:
      timezone: Asia/Kolkata
      start: 0 6 * * *
      end: 0 20 * * *
      desiredReplicas: "10"