External scalers receive metric names with internal KEDA core prefix

[tomkerkhove]

Discussed in #2635

^{Originally posted by krishna-kariya February 14, 2022}
Hi,
I am testing HTTP-triggered Azure Functions on Azure Arc with Keda version 2.5 and 2.6.1. We have created our external HTTP scaler on Keda for autoscaling.

I am getting the error below in the metrics API server
E0207 02:55:09.412436 1 status.go:71] apiserver received an error that is not an metav1.Status: &errors.errorString{s:"No matching metrics found for s0-upstream_rq_total"}: No matching metrics found for s0-upstream_rq_total.

The hpa shows a similar error:
invalid metrics (4 invalid out of 4), first error is: failed to get s0-upstream_rq_active external metric: unable to get external metric k8se-apps/s0-upstream_rq_active/&LabelSelector{MatchLabels:map[string]string{scaledobject.keda.sh/name: myapp,},MatchExpressions:[]LabelSelectorRequirement{},}: unable to fetch metrics from external metrics API: no matching metrics found for s0-upstream_rq_active

I see that from Keda v2.5 and later, the external metric names are prefixed with "sX-". Is this a new addition?
We have created our external HTTP scaler. Do we need to update our external HTTP scaler with these new metric names?

Any help would be appreciated. Thanks.

Tasklist

• Fix in KEDA core to pass correct metric name
• Provide e2e test(s)

End-users can mitigate this in their external scaler to remove the sX- prefix until we have shipped KEDA v2.6.2 or v2.7.0

[JorTurFer]

if nobody tackles this, next week I'll take a look at it

[tomkerkhove]

Thank you!

[v-shenoy]

Can take a look at this, if noone else is? @JorTurFer

[tomkerkhove]

That would be great, thanks @v-shenoy!