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Add Scheduling Configuration reference doc
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Built from the existing Scheduling Profiles doc.

Signed-off-by: Aldo Culquicondor <[email protected]>
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alculquicondor committed Jul 6, 2020
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Expand Up @@ -81,8 +81,8 @@ of the scheduler:

1. [Scheduling Policies](/docs/reference/scheduling/policies) allow you to
configure _Predicates_ for filtering and _Priorities_ for scoring.
1. [Scheduling Profiles](/docs/reference/scheduling/profiles) allow you to
configure Plugins that implement different scheduling stages, including:
1. [Scheduling Profiles](/docs/reference/scheduling/config/#profiles) allow you
to configure Plugins that implement different scheduling stages, including:
`QueueSort`, `Filter`, `Score`, `Bind`, `Reserve`, `Permit`, and others. You
can also configure the kube-scheduler to run different profiles.

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Expand Up @@ -228,7 +228,7 @@ type PreFilterPlugin interface {

You can enable or disable plugins in the scheduler configuration. If you are using
Kubernetes v1.18 or later, most scheduling
[plugins](/docs/reference/scheduling/profiles/#scheduling-plugins) are in use and
[plugins](/docs/reference/scheduling/config/#scheduling-plugins) are in use and
enabled by default.

In addition to default plugins, you can also implement your own scheduling
Expand All @@ -237,5 +237,5 @@ plugins and get them configured along with default plugins. You can visit

If you are using Kubernetes v1.18 or later, you can configure a set of plugins as
a scheduler profile and then define multiple profiles to fit various kinds of workload.
Learn more at [multiple profiles](/docs/reference/scheduling/profiles/#multiple-profiles).
Learn more at [multiple profiles](/docs/reference/scheduling/config/#multiple-profiles).

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Expand Up @@ -195,7 +195,7 @@ topology spread constraints are applied to a Pod if, and only if:
- It belongs to a service, replication controller, replica set or stateful set.
Default constraints can be set as part of the `PodTopologySpread` plugin args
in a [scheduling profile](/docs/reference/scheduling/profiles).
in a [scheduling profile](/docs/reference/scheduling/config/#profiles).
The constraints are specified with the same [API above](#api), except that
`labelSelector` must be empty. The selectors are calculated from the services,
replication controllers, replica sets or stateful sets that the Pod belongs to.
Expand All @@ -219,7 +219,7 @@ profiles:
{{< note >}}
The score produced by default scheduling constraints might conflict with the
score produced by the
[`DefaultPodTopologySpread` plugin](/docs/reference/scheduling/profiles/#scheduling-plugins).
[`DefaultPodTopologySpread` plugin](/docs/reference/scheduling/config/#scheduling-plugins).
It is recommended that you disable this plugin in the scheduling profile when
using default constraints for `PodTopologySpread`.
{{< /note >}}
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2 changes: 1 addition & 1 deletion content/en/docs/reference/_index.md
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Expand Up @@ -46,7 +46,7 @@ client libraries:
* [kube-proxy](/docs/reference/command-line-tools-reference/kube-proxy/) - Can do simple TCP/UDP stream forwarding or round-robin TCP/UDP forwarding across a set of back-ends.
* [kube-scheduler](/docs/reference/command-line-tools-reference/kube-scheduler/) - Scheduler that manages availability, performance, and capacity.
* [kube-scheduler Policies](/docs/reference/scheduling/policies)
* [kube-scheduler Profiles](/docs/reference/scheduling/profiles)
* [kube-scheduler Profiles](/docs/reference/scheduling/config#profiles)

## Design Docs

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@@ -1,30 +1,57 @@
---
title: Scheduling Profiles
title: Scheduler Configuration
content_type: concept
weight: 20
---

{{< feature-state for_k8s_version="v1.19" state="beta" >}}

The `KubeSchedulerConfiguration` is a configuration API for `kube-scheduler`
that can be provided as a file via `--config` command line flag.

<!-- overview -->

{{< feature-state for_k8s_version="v1.18" state="alpha" >}}
<!-- body -->

A scheduling Profile allows you to configure the different stages of scheduling
in the {{< glossary_tooltip text="kube-scheduler" term_id="kube-scheduler" >}}.
Each stage is exposed in a extension point. Plugins provide scheduling behaviors
by implementing one or more of these extension points.
## Minimal Configuration

You can specify scheduling profiles by running `kube-scheduler --config <filename>`,
using the component config APIs
([`v1alpha1`](https://pkg.go.dev/k8s.io/kube-scheduler@{{< param "fullversion" >}}/config/v1alpha1?tab=doc#KubeSchedulerConfiguration)
or [`v1alpha2`](https://pkg.go.dev/k8s.io/kube-scheduler@{{< param "fullversion" >}}/config/v1alpha2?tab=doc#KubeSchedulerConfiguration)).
The `v1alpha2` API allows you to configure kube-scheduler to run
[multiple profiles](#multiple-profiles).
A minimal configuration looks as follows:

```yaml
apiVersion: kubescheduler.config.k8s.io/v1beta1
kind: KubeSchedulerConfiguration
clientConnection:
kubeconfig: /etc/srv/kubernetes/kube-scheduler/kubeconfig
```
## Upgrading from `v1alpha2` to `v1beta1` {#beta-changes}

<!-- body -->
When migrating from `kubescheduler.config.k8s.io/v1alpha2` to `kubescheduler.config.k8s.io/v1beta1`,
beware of the following changes, if applicable:

- `.bindTimeoutSeconds` was moved as part of plugin args for `VolumeBinding`,
which can be configured separately per [profile](#profiles).
- `.extenders` are updated to satisfy API standards. In particular:
- `.extenders` decoding is case sensitive. All fields are affected.
- `.extenders[*].httpTimeout` is of type `metav1.Duration`.
- `.extenders[*].enableHttps` is renamed to `.extenders[*].enableHTTPS`.
- `RequestedToCapacityRatio` args decoding is case sensitive. All fields are affected.
- `DefaultPodTopologySpread` [plugin](#scheduling-plugins) is renamed to `SelectorSpread`.
- `Unreserve` extension point is removed from Profile definition. All `Reserve`
plugins implement an `Unreserve` call.

## Profiles

## Extension points
A scheduling Profile allows you to configure the different stages of scheduling
in the {{< glossary_tooltip text="kube-scheduler" term_id="kube-scheduler" >}}.
Each stage is exposed in a [extension point](#extension-points).
[Plugins](#scheduling-plugins) provide scheduling behaviors by implementing one
or more of these extension points.

A single instance of `kube-scheduler` can be configured to run
[multiple profiles](#multiple-profiles)

### Extension points

Scheduling happens in a series of stages that are exposed through the following
extension points:
Expand All @@ -43,23 +70,45 @@ extension points:
filtering phase. The scheduler will then select the node with the highest
weighted scores sum.
1. `Reserve`: This is an informational extension point that notifies plugins
when resources have being reserved for a given Pod.
when resources have being reserved for a given Pod. Plugins also implement an
`Unreserve` call, that gets called in the case of failure during of after
`Reserve`.
1. `Permit`: These plugins can prevent or delay the binding of a Pod.
1. `PreBind`: These plugins perform any work required before a Pod is bound.
1. `Bind`: The plugins bind a Pod to a Node. Bind plugins are called in order
and once one has done the binding, the remaining plugins are skipped. At
least one bind plugin is required.
1. `PostBind`: This is an informational extension point that is called after
a Pod has been bound.
1. `UnReserve`: This is an informational extension point that is called if
a Pod is rejected after being reserved and put on hold by a `Permit` plugin.

For each extension point, you could disable specific [default plugins](#scheduling-plugins)
or enable your own. For example:

```yaml
apiVersion: kubescheduler.config.k8s.io/v1beta1
kind: KubeSchedulerConfiguration
profiles:
- plugins:
score:
disabled:
- name: NodeResourcesLeastAllocated
enabled:
- name: MyCustomPluginA
weight: 2
- name: MyCustomPluginB
weight: 1
```

You can use `*` as name in the disabled array to disable all default plugins
for that extension point. This can also be used to rearrange plugins order, if
desired.

## Scheduling plugins
### Scheduling plugins

The following plugins, enabled by default, implement one or more of these
extension points:

- `DefaultTopologySpread`: Favors spreading across nodes for Pods that belong to
- `SelectorSpread`: Favors spreading across nodes for Pods that belong to
{{< glossary_tooltip text="Services" term_id="service" >}},
{{< glossary_tooltip text="ReplicaSets" term_id="replica-set" >}} and
{{< glossary_tooltip text="StatefulSets" term_id="statefulset" >}}
Expand Down Expand Up @@ -99,7 +148,7 @@ extension points:
Extension points: `Score`.
- `VolumeBinding`: Checks if the node has or if it can bind the requested
{{< glossary_tooltip text="volumes" term_id="volume" >}}.
Extension points: `Filter`.
Extension points: `PreFilter`, `Filter`, `Reserve`, `PreBind`.
- `VolumeRestrictions`: Checks that volumes mounted in the node satisfy
restrictions that are specific to the volume provider.
Extension points: `Filter`.
Expand Down Expand Up @@ -147,10 +196,25 @@ that are not enabled by default:
Service across nodes.
Extension points: `PreFilter`, `Filter`, `Score`.

## Multiple profiles
### Multiple profiles

`kube-scheduler` can be configured to
run more than one profile. Each profile has an associated scheduler name. Each
profile can have a different set of plugins configured in its
[extension points](#extension-points).

```yaml
apiVersion: kubescheduler.config.k8s.io/v1beta1
kind: KubeSchedulerConfiguration
profiles:
- schedulerName: default-scheduler
- schedulerName: no-scoring-scheduler
plugins:
score:
disabled:
- name: '*'
```

When using the component config API v1alpha2, a scheduler can be configured to
run more than one profile. Each profile has an associated scheduler name.
Pods that want to be scheduled according to a specific profile can include
the corresponding scheduler name in its `.spec.schedulerName`.

Expand All @@ -174,8 +238,6 @@ the same configuration parameters (if applicable). This is because the scheduler
only has one pending pods queue.
{{< /note >}}



## {{% heading "whatsnext" %}}

* Learn about [scheduling](/docs/concepts/scheduling-eviction/kube-scheduler/)
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Expand Up @@ -122,5 +122,5 @@ The following *priorities* implement scoring:
## {{% heading "whatsnext" %}}

* Learn about [scheduling](/docs/concepts/scheduling-eviction/kube-scheduler/)
* Learn about [kube-scheduler profiles](/docs/reference/scheduling/profiles/)
* Learn about [kube-scheduler Configuration](/docs/reference/scheduling/config/)

1 change: 1 addition & 0 deletions static/_redirects
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/docs/reference/glossary/maintainer/ /docs/reference/glossary/approver/ 301

/docs/reference/kubectl/kubectl/kubectl_*.md /docs/reference/generated/kubectl/kubectl-commands#:splat 301
/docs/reference/scheduling/profiles/ /docs/reference/scheduling/config/#profiles 301

/docs/reporting-security-issues/ /security/ 301

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