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Update horizontal_pod_autoscaling.md

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John Gardiner Myers 2020-05-31 21:59:21 -07:00
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# Horizontal Pod Autoscaling
With Horizontal Pod Autoscaling, Kubernetes automatically scales the number of
pods in a replication controller, deployment or replica set based on observed
pods in a replication controller, deployment, or replica set based on observed
CPU utilization (or, with alpha support, on some other, application-provided
metrics).
The current stable version, which only includes support for CPU autoscaling, can
be found in the `autoscaling/v1` API version. The alpha version, which includes
support for scaling on memory and custom metrics, can be found in
`autoscaling/v2alpha1` in 1.7 and `autoscaling/v2beta1` 1.8 and 1.9.
`autoscaling/v2beta1` (and `autoscaling/v2beta2` in 1.12 and later).
Kops can assist in setting up HPA and recommends Kubernetes `1.7.x` to `1.9.x`
and Kops `>=1.7`. Relevant reading you will need to go through:
Kops can assist in setting up HPA. Relevant reading you will need to go through:
* [Extending the Kubernetes API with the aggregation layer][k8s-extend-api]
* [Configure The Aggregation Layer][k8s-aggregation-layer]
@ -35,102 +34,25 @@ Specifically:
* [x] `--horizontal-pod-autoscaler-use-rest-clients` should be true.
* [x] `--kubeconfig <path-to-kubeconfig>`
Ensure that you use **1.8.5 at minimum for Kubernetes 1.8.x** due to [a nasty
bug affecting the API aggregation layer][issue-1]. It was fixed in
[kubernetes/kubernetes#55259][pr-5].
## Cluster Configuration
### Support For Multiple Metrics
Enable API versions required to support scaling on cpu, memory and custom
metrics:
```yaml
# On K8s 1.7
spec:
kubeAPIServer:
runtimeConfig:
autoscaling/v2alpha1: "true"
```
```yaml
# On K8s 1.8 and 1.9
spec:
kubeAPIServer:
runtimeConfig:
autoscaling/v2beta1: "true"
```
If you've set the above configuration, your cluster is now ready for the
resource metrics API ([installation instruction here][k8s-metrics-server]). The
To enable the resource metrics API for scaling on CPU and memory, install metrics-server
([installation instruction here][k8s-metrics-server]). The
compatibility matrix is as follows:
Metrics Server | Metrics API group/version | Supported Kubernetes version
---------------|---------------------------|-----------------------------
0.3.x | `metrics.k8s.io/v1beta1` | 1.8+
0.2.x | `metrics.k8s.io/v1beta1` | 1.8+
0.1.x | `metrics/v1alpha1` | 1.7
### Support For Custom Metrics
Enable gathering custom metrics:
```yaml
spec:
kubelet:
enableCustomMetrics: true
```
Note that the deprecated and inactive option '--enable-custom-metrics' has been removed in Kubernetes 1.11 [#60699](https://github.com/kubernetes/kubernetes/pull/60699)
Enable the horizontal pod autoscaler REST client:
```yaml
spec:
kubeControllerManager:
horizontalPodAutoscalerUseRestClients: true
```
If you've set the above configuration, your cluster is now ready for the custom
metrics API. Register it via the API aggregation layer. If you're using
To enable the custom metrics API, register it via the API aggregation layer. If you're using
Prometheus, checkout the [custom metrics adapter for Prometheus][k8s-prometheus-custom-metrics-adapter].
## Implementation Details
These are the PRs that enable the required configuration:
* [kubernetes/kops#3679][pr-1] - sets `--requestheader-xxx` kube-apiserver flags
required to enable aggregation layer
```
--requestheader-client-ca-file=<path to aggregator CA cert>
--requestheader-allowed-names=aggregator
--requestheader-extra-headers-prefix=X-Remote-Extra-
--requestheader-group-headers=X-Remote-Group
--requestheader-username-headers=X-Remote-User
```
* [kubernetes/kops#3165][pr-2] - sets `--proxy-client-xxx` kube-apiserver flags
required to enable aggregation layer
```
--proxy-client-cert-file=<path to aggregator proxy cert>
--proxy-client-key-file=<path to aggregator proxy key>
```
* [kubernetes/kops#3939][pr-3] - add config option to set `--horizontal-pod-
autoscaler-use-rest-clients` kube-controller-manager flag required to enable
custom metrics
* [kubernetes/kops#1574][pr-4] - add config options to set `--enable-custom-
metrics` flag on master and node kubelets required to enable custom metrics
[k8s-aggregation-layer]: https://v1-9.docs.kubernetes.io/docs/tasks/access-kubernetes-api/configure-aggregation-layer/
[k8s-extend-api]: https://v1-9.docs.kubernetes.io/docs/concepts/api-extension/apiserver-aggregation/
[k8s-hpa]: https://v1-9.docs.kubernetes.io/docs/tasks/run-application/horizontal-pod-autoscale/
[k8s-aggregation-layer]: https://kubernetes.io/docs/tasks/access-kubernetes-api/configure-aggregation-layer/
[k8s-extend-api]: https://kubernetes.io/docs/concepts/extend-kubernetes/api-extension/apiserver-aggregation/
[k8s-hpa]: https://kubernetes.io/docs/tasks/run-application/horizontal-pod-autoscale/
[k8s-metrics-server]: https://github.com/kubernetes/kops/blob/master/addons/metrics-server/README.md
[k8s-prometheus-custom-metrics-adapter]: https://github.com/DirectXMan12/k8s-prometheus-adapter
[pr-1]: https://github.com/kubernetes/kops/pull/3679
[pr-2]: https://github.com/kubernetes/kops/pull/3165
[pr-3]: https://github.com/kubernetes/kops/pull/3939
[pr-4]: https://github.com/kubernetes/kops/pull/1574
[pr-5]: https://github.com/kubernetes/kubernetes/pull/55259
[issue-1]: https://github.com/kubernetes/kubernetes/issues/55022