Update the explanation for `spec.high-availability` in operator doc (#4320)

* Update the explanation for `spec.high-availability` in operator doc

* Update docs/admin/install/operator/configuring-serving-cr.md

Co-authored-by: Samia Nneji <snneji@vmware.com>

* Update docs/admin/install/operator/configuring-serving-cr.md

Co-authored-by: Samia Nneji <snneji@vmware.com>

* Update docs/admin/install/operator/configuring-serving-cr.md

Co-authored-by: Samia Nneji <snneji@vmware.com>

Co-authored-by: Samia Nneji <snneji@vmware.com>
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Kenjiro Nakayama 2021-10-07 02:21:45 +09:00 committed by GitHub
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@ -344,9 +344,9 @@ spec:
## High availability
By default, Knative Serving runs a single instance of each controller. The `spec.high-availability` field allows you to configure the number of replicas for the following leader-elected controllers: `controller`, `autoscaler-hpa`, `net-istio-controller`. This field also configures the `HorizontalPodAutoscaler` resources for the data plane (`activator`):
By default, Knative Serving runs a single instance of each deployment. The `spec.high-availability` field allows you to configure the number of replicas for all deployments managed by the operator.
The following configuration specifies a replica count of 3 for the controllers and a minimum of 3 activators (which may scale higher if needed):
The following configuration specifies a replica count of 3 for the deployments:
```yaml
apiVersion: operator.knative.dev/v1alpha1
@ -359,6 +359,22 @@ spec:
replicas: 3
```
The `replicas` field also configures the `HorizontalPodAutoscaler` resources based on the `spec.high-availability`. Let's say the operator includes the following HorizontalPodAutoscaler:
```yaml
apiVersion: autoscaling/v2beta2
kind: HorizontalPodAutoscaler
metadata:
...
spec:
minReplicas: 3
maxReplicas: 5
```
If you configure `replicas: 2`, which is less than `minReplicas`, the operator transforms `minReplicas` to `1`.
If you configure `replicas: 6`, which is more than `maxReplicas`, the operator transforms `maxReplicas` to `maxReplicas + (replicas - minReplicas)` which is `8`.
## System Resource Settings
The operator custom resource allows you to configure system resources for the Knative system containers.