whentimeslows/website
1
0
Fork 0
Code Issues Pull Requests Actions Packages Projects Releases Wiki Activity

HPA: cleanup some nits, based on a readthrough of the docs

Browse Source
This commit is contained in:
Justin Santa Barbara
2016-06-12 14:56:04 -04:00
parent 73df8c3959
commit 43705be9fb
2 changed files with 40 additions and 40 deletions
Download Patch File Download Diff File Expand all files Collapse all files
docs/user-guide/horizontal-pod-autoscaling/index.md
+21 -20
View File
@@ -1,20 +1,21 @@
---
---
This document describes the current state of Horizontal Pod Autoscaler in Kubernetes.
This document describes the current state of Horizontal Pod Autoscaling in Kubernetes.
## What is Horizontal Pod Autoscaler?
Horizontal pod autoscaling allows to automatically scale the number of pods
## What is 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 CPU utilization.
The autoscaler is implemented as a Kubernetes API resource and a controller.
The resource describes behavior of the controller.
The Horizontal Pod Autoscaler is implemented as a Kubernetes API resource and a controller.
The resource determines the behavior of the controller.
The controller periodically adjusts the number of replicas in a replication controller or deployment
to match the observed average CPU utilization to the target specified by user.
## How does Horizontal Pod Autoscaler work?
## How does the Horizontal Pod Autoscaler work?
![Horizontal Pod Autoscaler diagram](/images/docs/horizontal-pod-autoscaler.svg)
@@ -29,34 +30,34 @@ Please note that if some of the pod's containers do not have CPU request set,
CPU utilization for the pod will not be defined and the autoscaler will not take any action.
Further details of the autoscaling algorithm are given [here](https://github.com/kubernetes/kubernetes/blob/{{page.githubbranch}}/docs/design/horizontal-pod-autoscaler.md#autoscaling-algorithm).
Autoscaler uses heapster to collect CPU utilization.
The autoscaler uses heapster to collect CPU utilization.
Therefore, it is required to deploy heapster monitoring in your cluster for autoscaling to work.
Autoscaler accesses corresponding replication controller, deployment or replica set by scale sub-resource.
The autoscaler accesses corresponding replication controller, deployment or replica set by scale sub-resource.
Scale is an interface which allows to dynamically set the number of replicas and to learn the current state of them.
More details on scale sub-resource can be found [here](https://github.com/kubernetes/kubernetes/blob/{{page.githubbranch}}/docs/design/horizontal-pod-autoscaler.md#scale-subresource).
## API Object
Horizontal pod autoscaler is a top-level resource in the Kubernetes REST API.
Horizontal Pod Autoscaler is a top-level resource in the Kubernetes REST API.
In Kubernetes 1.2 HPA was graduated from beta to stable (more details about [api versioning](/docs/api/#api-versioning)) with compatibility between versions.
The stable version is available in `autoscaling/v1` api group whereas the beta vesion is available in `extensions/v1beta1` api group as before.
The transition plan is to depracate beta version of HPA in Kubernetes 1.3 and get it rid off completely in Kubernetes 1.4.
The stable version is available in the `autoscaling/v1` api group whereas the beta vesion is available in the `extensions/v1beta1` api group as before.
The transition plan is to deprecate beta version of HPA in Kubernetes 1.3, and get it rid off completely in Kubernetes 1.4.
**Warning!** Please have in mind that all Kubernetes components still use HPA in version `extensions/v1beta1` in Kubernetes 1.2.
**Warning!** Please have in mind that all Kubernetes components still use HPA in `extensions/v1beta1` in Kubernetes 1.2.
More details about the API object can be found at
[HorizontalPodAutoscaler Object](https://github.com/kubernetes/kubernetes/blob/{{page.githubbranch}}/docs/design/horizontal-pod-autoscaler.md#horizontalpodautoscaler-object).
## Support for horizontal pod autoscaler in kubectl
## Support for Horizontal Pod Autoscaler in kubectl
Horizontal pod autoscaler, like every API resource, is supported in a standard way by `kubectl`.
Horizontal Pod Autoscaler, like every API resource, is supported in a standard way by `kubectl`.
We can create a new autoscaler using `kubectl create` command.
We can list autoscalers by `kubectl get hpa` and get detailed description by `kubectl describe hpa`.
Finally, we can delete an autoscaler using `kubectl delete hpa`.
In addition, there is a special `kubectl autoscale` command that allows for easy creation of horizontal pod autoscaler.
In addition, there is a special `kubectl autoscale` command for easy creation of a Horizontal Pod Autoscaler.
For instance, executing `kubectl autoscale rc foo --min=2 --max=5 --cpu-percent=80`
will create an autoscaler for replication controller *foo*, with target CPU utilization set to `80%`
and the number of replicas between 2 and 5.
@@ -67,17 +68,17 @@ The detailed documentation of `kubectl autoscale` can be found [here](/docs/user
Currently in Kubernetes, it is possible to perform a rolling update by managing replication controllers directly,
or by using the deployment object, which manages the underlying replication controllers for you.
Horizontal pod autoscaler only supports the latter approach: the horizontal pod autoscaler is bound to the deployment object,
Horizontal Pod Autoscaler only supports the latter approach: the Horizontal Pod Autoscaler is bound to the deployment object,
it sets the size for the deployment object, and the deployment is responsible for setting sizes of underlying replication controllers.
Horizontal pod autoscaler does not work with rolling update using direct manipulation of replication controllers,
i.e. you cannot bind a horizontal pod autoscaler to a replication controller and do rolling update (e.g. using `kubectl rolling-update`).
Horizontal Pod Autoscaler does not work with rolling update using direct manipulation of replication controllers,
i.e. you cannot bind a Horizontal Pod Autoscaler to a replication controller and do rolling update (e.g. using `kubectl rolling-update`).
The reason this doesn't work is that when rolling update creates a new replication controller,
the horizontal pod autoscaler will not be bound to the new replication controller.
the Horizontal Pod Autoscaler will not be bound to the new replication controller.
## Further reading
* Design documentation: [Horizontal Pod Autoscaling](https://github.com/kubernetes/kubernetes/blob/{{page.githubbranch}}/docs/design/horizontal-pod-autoscaler.md).
* Manual of autoscale command in kubectl: [kubectl autoscale](/docs/user-guide/kubectl/kubectl_autoscale).
* kubectl autoscale command: [kubectl autoscale](/docs/user-guide/kubectl/kubectl_autoscale).
* Usage example of [Horizontal Pod Autoscaler](/docs/user-guide/horizontal-pod-autoscaling/walkthrough/).