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add migration docs for scheduler component config api from v1beta2 to…
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… v1beta3

Signed-off-by: kerthcet <kerthcet@gmail.com>
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kerthcet committed Nov 24, 2021
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33 changes: 7 additions & 26 deletions content/en/docs/reference/scheduling/config.md
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Expand Up @@ -20,8 +20,7 @@ by implementing one or more of these extension points.

You can specify scheduling profiles by running `kube-scheduler --config <filename>`,
using the
KubeSchedulerConfiguration ([v1beta1](/docs/reference/config-api/kube-scheduler-config.v1beta1/)
or [v1beta2](/docs/reference/config-api/kube-scheduler-config.v1beta2/))
KubeSchedulerConfiguration ([v1beta2](/docs/reference/config-api/kube-scheduler-config.v1beta2/))
struct.

A minimal configuration looks as follows:
Expand Down Expand Up @@ -179,30 +178,6 @@ that are not enabled by default:
volume limits can be satisfied for the node.
Extension points: `filter`.

The following plugins are deprecated and can only be enabled in a `v1beta1`
configuration:

- `NodeResourcesLeastAllocated`: Favors nodes that have a low allocation of
resources.
Extension points: `score`.
- `NodeResourcesMostAllocated`: Favors nodes that have a high allocation of
resources.
Extension points: `score`.
- `RequestedToCapacityRatio`: Favor nodes according to a configured function of
the allocated resources.
Extension points: `score`.
- `NodeLabel`: Filters and / or scores a node according to configured
{{< glossary_tooltip text="label(s)" term_id="label" >}}.
Extension points: `filter`, `score`.
- `ServiceAffinity`: Checks that Pods that belong to a
{{< glossary_tooltip term_id="service" >}} fit in a set of nodes defined by
configured labels. This plugin also favors spreading the Pods belonging to a
Service across nodes.
Extension points: `preFilter`, `filter`, `score`.
- `NodePreferAvoidPods`: Prioritizes nodes according to the node annotation
`scheduler.alpha.kubernetes.io/preferAvoidPods`.
Extension points: `score`.

### Multiple profiles

You can configure `kube-scheduler` to run more than one profile.
Expand Down Expand Up @@ -285,7 +260,13 @@ only has one pending pods queue.
* A plugin enabled in a v1beta2 configuration file takes precedence over the default configuration for that plugin.

* Invalid `host` or `port` configured for scheduler healthz and metrics bind address will cause validation failure.
{{% /tab %}}

{{% tab name="v1beta2 → v1beta3" %}}
* Three plugins' weight are increased by default:
* `InterPodAffinity` from 1 to 2
* `NodeAffinity` from 1 to 2
* `TaintToleration` from 1 to 3
{{% /tab %}}
{{< /tabs >}}

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92 changes: 3 additions & 89 deletions content/en/docs/reference/scheduling/policies.md
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Expand Up @@ -11,99 +11,13 @@ that the {{< glossary_tooltip text="kube-scheduler" term_id="kube-scheduler" >}}
runs to [filter and score nodes](/docs/concepts/scheduling-eviction/kube-scheduler/#kube-scheduler-implementation),
respectively.

You can set a scheduling policy by running
`kube-scheduler --policy-config-file <filename>` or
`kube-scheduler --policy-configmap <ConfigMap>`
and using the [Policy type](/docs/reference/config-api/kube-scheduler-policy-config.v1/).

<!-- body -->

## Predicates

The following *predicates* implement filtering:

- `PodFitsHostPorts`: Checks if a Node has free ports (the network protocol kind)
for the Pod ports the Pod is requesting.

- `PodFitsHost`: Checks if a Pod specifies a specific Node by its hostname.

- `PodFitsResources`: Checks if the Node has free resources (eg, CPU and Memory)
to meet the requirement of the Pod.

- `MatchNodeSelector`: Checks if a Pod's Node {{< glossary_tooltip term_id="selector" >}}
matches the Node's {{< glossary_tooltip text="label(s)" term_id="label" >}}.

- `NoVolumeZoneConflict`: Evaluate if the {{< glossary_tooltip text="Volumes" term_id="volume" >}}
that a Pod requests are available on the Node, given the failure zone restrictions for
that storage.

- `NoDiskConflict`: Evaluates if a Pod can fit on a Node due to the volumes it requests,
and those that are already mounted.

- `MaxCSIVolumeCount`: Decides how many {{< glossary_tooltip text="CSI" term_id="csi" >}}
volumes should be attached, and whether that's over a configured limit.

- `PodToleratesNodeTaints`: checks if a Pod's {{< glossary_tooltip text="tolerations" term_id="toleration" >}}
can tolerate the Node's {{< glossary_tooltip text="taints" term_id="taint" >}}.

- `CheckVolumeBinding`: Evaluates if a Pod can fit due to the volumes it requests.
This applies for both bound and unbound
{{< glossary_tooltip text="PVCs" term_id="persistent-volume-claim" >}}.

## Priorities

The following *priorities* implement scoring:

- `SelectorSpreadPriority`: Spreads Pods across hosts, considering Pods that
belong to the same {{< glossary_tooltip text="Service" term_id="service" >}},
{{< glossary_tooltip term_id="statefulset" >}} or
{{< glossary_tooltip term_id="replica-set" >}}.

- `InterPodAffinityPriority`: Implements preferred
[inter pod affininity and antiaffinity](/docs/concepts/scheduling-eviction/assign-pod-node/#inter-pod-affinity-and-anti-affinity).

- `LeastRequestedPriority`: Favors nodes with fewer requested resources. In other
words, the more Pods that are placed on a Node, and the more resources those
Pods use, the lower the ranking this policy will give.

- `MostRequestedPriority`: Favors nodes with most requested resources. This policy
will fit the scheduled Pods onto the smallest number of Nodes needed to run your
overall set of workloads.

- `RequestedToCapacityRatioPriority`: Creates a requestedToCapacity based ResourceAllocationPriority using default resource scoring function shape.

- `BalancedResourceAllocation`: Favors nodes with balanced resource usage.

- `NodePreferAvoidPodsPriority`: Prioritizes nodes according to the node annotation
`scheduler.alpha.kubernetes.io/preferAvoidPods`. You can use this to hint that
two different Pods shouldn't run on the same Node.

- `NodeAffinityPriority`: Prioritizes nodes according to node affinity scheduling
preferences indicated in PreferredDuringSchedulingIgnoredDuringExecution.
You can read more about this in [Assigning Pods to Nodes](/docs/concepts/scheduling-eviction/assign-pod-node/).

- `TaintTolerationPriority`: Prepares the priority list for all the nodes, based on
the number of intolerable taints on the node. This policy adjusts a node's rank
taking that list into account.

- `ImageLocalityPriority`: Favors nodes that already have the
{{< glossary_tooltip text="container images" term_id="image" >}} for that
Pod cached locally.

- `ServiceSpreadingPriority`: For a given Service, this policy aims to make sure that
the Pods for the Service run on different nodes. It favours scheduling onto nodes
that don't have Pods for the service already assigned there. The overall outcome is
that the Service becomes more resilient to a single Node failure.

- `EqualPriority`: Gives an equal weight of one to all nodes.

- `EvenPodsSpreadPriority`: Implements preferred
[pod topology spread constraints](/docs/concepts/workloads/pods/pod-topology-spread-constraints/).
{{< warning >}}
This scheduling policy is not longer supported, associated flags `policy-config-file`, `policy-configmap`, `policy-configmap-namespace` and `use-legacy-policy-config` are also removed. Instead, use the [Scheduler Configuration](/docs/reference/scheduling/config/) to achieve similar behavior.
{{< /warning >}}

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

* Learn about [scheduling](/docs/concepts/scheduling-eviction/kube-scheduler/)
* Learn about [kube-scheduler Configuration](/docs/reference/scheduling/config/)
* Read the [kube-scheduler configuration reference (v1beta2)](/docs/reference/config-api/kube-scheduler-config.v1beta2)
* Read the [kube-scheduler Policy reference (v1)](/docs/reference/config-api/kube-scheduler-policy-config.v1/)

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