Datadog trigger is being included into the composite-metric unexpectedly.

[devkoriel]

Report

I am using scalingModifiers to make composite-metric using metric-api triggers but when I add datadog trigger metric, it's also forced to be included into composite-metric not as I expected.

Expected Behavior

I expected the new external section to be added in HPA.

Actual Behavior

I am using scalingModifiers to make composite-metric using metric-api triggers but when I add datadog trigger metric, it's also forced to be included into composite-metric not as I expected.

Steps to Reproduce the Problem

1. Use composite-metric by adding scalingModifier.
2. Add datadog trigger.
3. It happens.

Logs from KEDA operator

2024-01-12T03:54:29Z	ERROR	scale_handler	error pairing triggers & metrics for compositeScaler	{"scaledObject.Namespace": "engine", "scaledObject.Name": "engine-open-api", "error": "trigger name not given with compositeScaler for metric s4-datadog-sum-kubernetes_state-deployment-replicas_desired"}
github.com/kedacore/keda/v2/pkg/scaling.(*scaleHandler).getScalerState
	/workspace/pkg/scaling/scale_handler.go:744
github.com/kedacore/keda/v2/pkg/scaling.(*scaleHandler).getScaledObjectState
	/workspace/pkg/scaling/scale_handler.go:590
github.com/kedacore/keda/v2/pkg/scaling.(*scaleHandler).checkScalers
	/workspace/pkg/scaling/scale_handler.go:241
github.com/kedacore/keda/v2/pkg/scaling.(*scaleHandler).startScaleLoop
	/workspace/pkg/scaling/scale_handler.go:180

KEDA Version

2.12.1

Kubernetes Version

1.26

Platform

Amazon Web Services

Scaler Details

kubernetes-workload, metrics-api, cpu, datadog

Anything else?

We are operating k8s using kops on AWS.

[JorTurFer]

Hello,
This is done as design, when you work with scaling modifiers, all the triggers are treated as sources for the formula.
I see that you are using CPU trigger too, but it is not supported for composition.
As the HPA Controller does a Max between all the exposed metrics, you can include datadog scaler in your formula replicating that behavior, just with max(you_formula, datadog_scaler)

[devkoriel]

@JorTurFer Thank you for guiding. However, for now, I have to use cron trigger with scalingModifiers. Any workarounds or plans for this feature?

[JorTurFer]

I don't think so, because it makes the things quite complex (which metrics, why onyl one formula, etc), but I'd like to know the thoughts from @zroubalik and @tomkerkhove

[zroubalik]

Yeah, I am also inclined towards what @JorTurFer mentioned. The original desing of ScalingModifiers have been done this way. It would be extremely complicated. Just include it into the formula.