openshift-docs/modules/nodes-descheduler-installing.adoc

// Module included in the following assemblies:
//
// * nodes/scheduling/descheduler/nodes-descheduler-configuring.adoc

ifeval::["{context}" == "nodes-descheduler-about"]
:nodes:
endif::[]

ifeval::["{context}" == "virt-enabling-descheduler-evictions"]
:virt:
endif::[]

:_mod-docs-content-type: PROCEDURE
[id="nodes-descheduler-installing_{context}"]
= Installing the descheduler

The descheduler is not available by default. To enable the descheduler, you must install the {descheduler-operator} from OperatorHub and enable one or more descheduler profiles.

By default, the descheduler runs in predictive mode, which means that it only simulates pod evictions. You must change the mode to automatic for the descheduler to perform the pod evictions.

[IMPORTANT]
====
If you have enabled hosted control planes in your cluster, set a custom priority threshold to lower the chance that pods in the hosted control plane namespaces are evicted. Set the priority threshold class name to `hypershift-control-plane`, because it has the lowest priority value (`100000000`) of the hosted control plane priority classes.
====

.Prerequisites

ifndef::openshift-rosa,openshift-dedicated[]
* You are logged in to {product-title} as a user with the `cluster-admin` role.
endif::openshift-rosa,openshift-dedicated[]
ifdef::openshift-rosa,openshift-dedicated[]
* You are logged in to {product-title} as a user with the `dedicated-admin` role.
endif::openshift-rosa,openshift-dedicated[]
* Access to the {product-title} web console.
ifdef::openshift-origin[]
* Ensure that you have downloaded the {cluster-manager-url-pull} as shown in _Obtaining the installation program_ in the installation documentation for your platform.
+
If you have the pull secret, add the `redhat-operators` catalog to the OperatorHub custom resource (CR) as shown in _Configuring {product-title} to use Red Hat Operators_.
endif::[]

.Procedure

. Log in to the {product-title} web console.
. Create the required namespace for the {descheduler-operator}.
.. Navigate to *Administration* -> *Namespaces* and click *Create Namespace*.
.. Enter `openshift-kube-descheduler-operator` in the *Name* field, enter `openshift.io/cluster-monitoring=true` in the *Labels* field to enable descheduler metrics, and click *Create*.
. Install the {descheduler-operator}.
.. Navigate to *Operators* -> *OperatorHub*.
.. Type *{descheduler-operator}* into the filter box.
.. Select the *{descheduler-operator}* and click *Install*.
.. On the *Install Operator* page, select *A specific namespace on the cluster*. Select *openshift-kube-descheduler-operator* from the drop-down menu.
.. Adjust the values for the *Update Channel* and *Approval Strategy* to the desired values.
.. Click *Install*.
. Create a descheduler instance.
.. From the *Operators* -> *Installed Operators* page, click the *{descheduler-operator}*.
.. Select the *Kube Descheduler* tab and click *Create KubeDescheduler*.
.. Edit the settings as necessary.
... To evict pods instead of simulating the evictions, change the *Mode* field to *Automatic*.

ifdef::virt[]
... Expand the *Profiles* section and select `DevPreviewLongLifecycle`. The `AffinityAndTaints` profile is enabled by default.
+
[IMPORTANT]
====
The only profile currently available for {VirtProductName} is `DevPreviewLongLifecycle`.
====

You can also configure the profiles and settings for the descheduler later using the OpenShift CLI (`oc`).
endif::virt[]
ifdef::nodes[]
... Expand the *Profiles* section to select one or more profiles to enable. The `AffinityAndTaints` profile is enabled by default. Click *Add Profile* to select additional profiles.
+
[NOTE]
====
Do not enable both `TopologyAndDuplicates` and `SoftTopologyAndDuplicates`. Enabling both results in a conflict.
====
... Optional: Expand the *Profile Customizations* section to set optional configurations for the descheduler.
**** Set a custom pod lifetime value for the `LifecycleAndUtilization` profile. Use the *podLifetime* field to set a numerical value and a valid unit (`s`, `m`, or `h`). The default pod lifetime is 24 hours (`24h`).

**** Set a custom priority threshold to consider pods for eviction only if their priority is lower than a specified priority level. Use the *thresholdPriority* field to set a numerical priority threshold or use the *thresholdPriorityClassName* field to specify a certain priority class name.
+
[NOTE]
====
Do not specify both *thresholdPriority* and *thresholdPriorityClassName* for the descheduler.
====

**** Set specific namespaces to exclude or include from descheduler operations. Expand the *namespaces* field and add namespaces to the *excluded* or *included* list. You can only either set a list of namespaces to exclude or a list of namespaces to include. Note that protected namespaces (`openshift-*`, `kube-system`, `hypershift`) are excluded by default.

**** Experimental: Set thresholds for underutilization and overutilization for the `LowNodeUtilization` strategy. Use the *devLowNodeUtilizationThresholds* field to set one of the following values:
+
--
***** `Low`: 10% underutilized and 30% overutilized
***** `Medium`: 20% underutilized and 50% overutilized (Default)
***** `High`: 40% underutilized and 70% overutilized
--
+
[NOTE]
====
This setting is experimental and should not be used in a production environment.
====

... Optional: Use the *Descheduling Interval Seconds* field to change the number of seconds between descheduler runs. The default is `3600` seconds.
.. Click *Create*.

You can also configure the profiles and settings for the descheduler later using the OpenShift CLI (`oc`). If you did not adjust the profiles when creating the descheduler instance from the web console, the `AffinityAndTaints` profile is enabled by default.
endif::nodes[]

ifeval::["{context}" == "nodes-descheduler-about"]
:!nodes:
endif::[]

ifeval::["{context}" == "virt-enabling-descheduler-evictions"]
:!virt:
endif::[]