Problem with fetching Azure custom metric through Azure Monitor scaler

[dymitrs]

Discussed in #1946

^{Originally posted by dymitrs July 10, 2021}
Hi all,
It seems that the Monitor scaler does not work with some custom metrics from Application Insights.
According to docs and the PR, Custom Metrics are supported after those changes #1883.

  triggers:
  - type: azure-monitor
    metadata:
      resourceURI: Microsoft.Insights/Components/app-insights
      subscriptionId: <...>
      tenantId: <...>
      resourceGroupName: <...>
      metricName: customMetrics/<metric name>
      metricNamespace: azure.applicationinsights
      metricAggregationInterval: "0:3:0"
      metricAggregationType: Count
      targetValue: "{{ .Values.scale_settings.target_value }}"

The autoscaler works fine for "default" metrics but for my custom one I'm getting this error and it fails - log from Keda operator pod:

ERROR   azure_monitor_scaler    error getting azure monitor metric      {"error": "error getting azure monitor metric customMetrics/<metric name>: got metric result for Microsoft.Insights/customMet
rics/<metric name> and aggregate type COUNT without timeseries"}
github.com/kedacore/keda/v2/pkg/scaling.(*scaleHandler).isScaledObjectActive
        /workspace/pkg/scaling/scale_handler.go:216
github.com/kedacore/keda/v2/pkg/scaling.(*scaleHandler).checkScalers

Expected behavior:
Metrics are read from Azure.

Actual behavior:
Error getting metric.

Steps to reproduce:

1. Setup Monitor scaler.
2. Fetch custom metrics from Application Insights.

KEDA Version:
2.3.0

[tomkerkhove]

Let's take a look but for what it's worth, Azure Monitor custom metrics do not always have parity with Application Insights which can require different API usage.

[stale]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed in 7 days if no further activity occurs. Thank you for your contributions.

[ifutant]

Any update on the status of this?

[stale]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed in 7 days if no further activity occurs. Thank you for your contributions.

[tomkerkhove]

Checking if this is still a problem yo are facing @dymitrs @ifutant ?

[markrzasa]

I believe this is still a problem. It does appear that Application Insights uses a different API than Azure monitor. Here's the doc:

https://dev.applicationinsights.io/reference

I created a PR to add an Application Insights scaler:
#2506
kedacore/keda-docs#638

However, this scaler may not be necessary as the Azure Log Analytics scaler can be used to read Application Insights metrics using the AppMetrics table.

[tomkerkhove]

Yes that is correct, I have misread the original report - Sorry :)

However, this scaler may not be necessary as the Azure Log Analytics scaler can be used to read Application Insights metrics using the AppMetrics table.

This is true, for the workspace-based Application Insights instances. The classic ones are still supported for 2-3 years so think a dedicated scaler might be better indeed.