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docs: Provide FAQ entry about using multiple installations & metric servers #950

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Sep 28, 2022
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docs: Provide FAQ entry about using multiple installations & metric servers #950

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docs: Provide FAQ entry about using multiple installations & metric s…
tomkerkhove Sep 28, 2022
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tomkerkhove Sep 28, 2022
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36 changes: 35 additions & 1 deletion data/faq20.toml
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Expand Up @@ -87,7 +87,41 @@ Because KEDA primarily serves metrics for metric sources outside of the Kubernet

This is why KEDA registers the `v1beta1.external.metrics.k8s.io` namespace in the API service. However, this is just an implementation detail as both offer the same functionality.

Read [this article](https://cloud.google.com/kubernetes-engine/docs/concepts/custom-and-external-metrics) by Google Cloud to learn more.
Read [about the different metric APIs](https://kubernetes.io/docs/tasks/run-application/horizontal-pod-autoscale/#support-for-metrics-apis) or [this article](https://cloud.google.com/kubernetes-engine/docs/concepts/custom-and-external-metrics) by Google Cloud to learn more.
"""
type = "Kubernetes"

[[qna]]
q = "Can I run multiple metric servers serving external metrics in the same cluster?"
a = """
Unfortunately, you cannot do that.

Kubernetes currently only supports one metric server serving `external.metrics.k8s.io` metrics per cluster. This is because only one API Service can be registered to handle external metrics.

If you want to know what external metric server is currently registered, you can use the following command:

```shell
~ kubectl get APIService/v1beta1.external.metrics.k8s.io
NAME SERVICE AVAILABLE AGE
v1beta1.external.metrics.k8s.io keda-system/keda-operator-metrics-apiserver True 457d
```

Once a new metric server is installed, it will overwrite the existing API Server registration and take over the `v1beta1.external.metrics.k8s.io` namespace. This will cause the previously installed metric server to be ignored.

There is an [open proposal](https://github.com/kubernetes-sigs/custom-metrics-apiserver/issues/70) to allow multiple metric servers in the same cluster, but it's not implemented yet.
"""
type = "Kubernetes"

[[qna]]
q = "Can I run multiple installations of KEDA in the same cluster?"
a = """
Unfortunately, you cannot do that.

This is a limitation that is because Kubernetes does not allow you to run multiple metric servers in the same cluster that serve external metrics.

Also, KEDA does not allow you to share a single metric server across multiple operator installations.

Learn more in the "Can I run multiple metric servers serving external metrics in the same cluster?" FAQ entry.
"""
type = "Kubernetes"

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