How to set CooldownPeriod for New-AzContainerAppScaleRuleObject via Powershell CLI

Hello @Brian Bento

You're looking in the right general area, but cooldownPeriod isn't actually a property of New AzContainerAppScaleRuleObject.

In the Azure Container Apps resource model, the structure is:

So cooldownPeriod applies to the Container App scaling configuration, not to an individual scaling rule. Microsoft currently documents it as an optional integer in seconds, with a default of 300 seconds when it isn't specified.

That's why you don't see a -CooldownPeriod parameter on:

New-AzContainerAppScaleRuleObject

Your $scaleRule construction is therefore only defining the rule itself:

$scaleRule = New-AzContainerAppScaleRuleObject `
    -Name "http-scaling-rule" `
    -CustomType "http" `
    -CustomMetadata @{"concurrentRequests"="1"}

The problem is that the current New-AzContainerApp PowerShell parameter set you're using exposes things such as ScaleMinReplica, ScaleMaxReplica, and ScaleRule, but doesn't expose the complete underlying template.scale model, including cooldownPeriod.

The ARM resource schema does expose it:

"template": {
  "scale": {
    "minReplicas": 0,
    "maxReplicas": 1,
    "cooldownPeriod": 60,
    "rules": [
      ...
    ]
  }
}

Microsoft documents that schema here:

Microsoft.App/containerApps ARM/Bicep reference

So if the Az PowerShell cmdlet/version you're using doesn't expose ScaleCooldownPeriod, don't put it in CustomMetadata. That metadata belongs to the scaler itself and isn't where Container Apps expects the KEDA cooldown setting.

Instead, use the ARM/Bicep representation (or another deployment method that exposes the complete template.scale object) and set: properties.template.scale.cooldownPeriod

For example, in Bicep:

template: {
  scale: {
    minReplicas: 0
    maxReplicas: 1
    cooldownPeriod: 60
    rules: [
      // scaling rule
    ]
  }
}

There is also a pollingInterval property at the same level if you need to control how frequently KEDA evaluates non-HTTP event sources; its documented default is 30 seconds.

So your assumption from the portal was correct: Cooldown Period belongs at the same logical scale level as Min Replicas and Max Replicas, not inside New-AzContainerAppScaleRuleObject. The confusing part is simply that the Az.ContainerApp PowerShell cmdlet doesn't necessarily expose every property available in the current Container Apps ARM schema.

If PowerShell is mandatory for your deployment pipeline, you can still deploy/update the ARM resource from PowerShell rather than relying exclusively on New-AzContainerApp's flattened parameters.

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Hi @Brian Bento ,

Thank you reaching out to Microsoft Q & A !

CooldownPeriod is not a property of New-AzContainerAppScaleRuleObject. That cmdlet creates an individual scaling rule, whereas the cooldown period is part of the overall Container App scale configuration.

The underlying Container Apps resource model defines cooldownPeriod at the same scale level as minReplicas, maxReplicas, pollingInterval, and rules. Microsoft documents the default cooldown period as 300 seconds when it isn't specified.

Therefore, you should not add cooldownPeriod to CustomMetadata, because that metadata belongs to the individual scaler.

One point to note is that the cooldown period applies when scaling in from the final replica to zero. It does not affect the removal of other replicas. This is particularly relevant in your configuration because you have ScaleMinReplica = 0.

If the Az.ContainerApp PowerShell cmdlet/version you're using doesn't expose the scale-level cooldown property, you can configure it through a deployment method that exposes the underlying Container Apps scale model, such as ARM/Bicep.

References:

• New-AzContainerAppScaleRuleObject
• Scaling in Azure Container Apps
• Microsoft.App/containerApps ARM/Bicep resource reference

Hope this clarifies the distinction between the scale rule and the scale-level cooldown configuration.

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