OSDOCS16065 Document InPlacePod Resize feature for OpenShift 4.20

_topic_maps/_topic_map.yml

@@ -2641,6 +2641,8 @@ Topics:
     File: nodes-pods-autoscaling
   - Name: Automatically adjust pod resource levels with the vertical pod autoscaler
     File: nodes-pods-vertical-autoscaler
+  - Name: Manually adjust pod resource levels
+    File: nodes-pods-adjust-resources-in-place
   - Name: Providing sensitive data to pods by using secrets
     File: nodes-pods-secrets
   - Name: Providing sensitive data to pods by using an external secrets store

modules/nodes-pods-adjust-resources-in-place-about.adoc

@@ -0,0 +1,125 @@
+// Module included in the following assemblies:
+//
+// * nodes/pods/nodes-pods-adjust-resources-in-place.adoc
+
+:_mod-docs-content-type: REFERENCE
+[id="nodes-pods-adjust-resources-in-place-about_{context}"]
+= About in-place pod resizing
+
+In-place pod resizing allows you to change the CPU and memory resources for containers within a running pod without application disruption. The standard methods for changing pod CPU and memory resources cause the pod to be re-created, potentially causing disruption. In-place pod resizing allows you to scale pod resources up or down without suffering the downtime or state loss associated with a pod restart.
+
+When using in-place pod resizing to change CPU or memory resources, you can control whether a pod is restarted by configuring a resize policy in the pod specification. The following example resize policy requires a pod restart upon changing the memory resources, but prevents a restart for CPU resource changes.
+
+.Example resource policy
+[source,yaml]
+----
+apiVersion: v1
+kind: Pod
+metadata:
+  name: resize-demo
+spec:
+  securityContext:
+    runAsNonRoot: true
+    seccompProfile:
+      type: RuntimeDefault
+  containers:
+  - name: pause
+# ...
+    resizePolicy: <1>
+    - resourceName: cpu
+      restartPolicy: NotRequired
+    - resourceName: memory
+      restartPolicy: RestartContainer
+----
+<1> Specifies a resize policy. 
+
+[NOTE]
+====
+Memory limits cannot be decreased unless the resize policy for `memory` is `RestartContainer`.
+====
+
+You cannot add or modify a resize policy to an existing pod, but you can add or edit the policy in the pod's owner object, such as a deployment, if the pod has an owner object. 
+
+Using in-place pod resizing requires that you use the `--subresource resize` flag when editing a pod in the {oc-first}, as shown in the following examples:
+
+.Example commands
+[source,terminal]
+----
+$ oc edit pod <pod_name>  --subresource resize
+----
+
+[source,terminal]
+----
+$ apply -f <file_name>.yaml --subresource resize
+----
+
+[source,terminal]
+----
+$ patch pod <pod_name> --subresource resize --patch \
+  '{"spec":{"containers":[{"name":"pause", "resources":{"requests":{"cpu":"800m"}, "limits":{"cpu":"800m"}}}]}}'
+----
+
+Because you need to use the `--subresource resize` flag with a resize policy, you cannot edit the pod resources in the {product-title} web console.
+
+If the resize policy is `NotRequired` and you change the request or limits, the pod is not restarted.
+
+[source,terminal]
+----
+$ oc get pods
+----
+
+.Example output
+[source,terminal]
+----
+NAME                          READY   STATUS    RESTARTS     AGE
+resize-pod                    1/1     Running   0            5s
+----
+
+If the resize policy is `RestartContainer` and you change the request or limits, the pod is restarted.
+
+[source,terminal]
+----
+$ oc get pods
+----
+
+.Example output
+[source,terminal]
+----
+NAME                         READY   STATUS    RESTARTS    AGE
+resize-pod                   1/1     Running   1 (5s ago)  5s
+----
+
+After making the resource changes, the pod status conditions indicate the state of a resize request by using the following messages:
+
+* `PodResizeInProgress`: The kubelet is able to allocate the requested resources and the change is being applied.
+* `PodResizePending`: The kubelet cannot immediately make the change for one of the following reasons:
+** `Infeasible`: The requested resize cannot be executed on the current node. For example, requesting more resources than the node has available would result in an `Infeasible` condition.
+** `Deferred`: The requested resize is currently not possible, but might become possible at a later time. For example, if another pod is removed from the node, the requested resources might become available. The kubelet retries the resize when conditions on the node change.
+* `Error`: The kubelet is experiencing an error during the resource allocation and reports the reason for the error in the message field.
+
+.Example status for an infeasible change
+[source,yaml]
+----
+apiVersion: v1
+kind: Pod
+metadata:
+  name: resize-demo
+# ...
+status:
+  conditions:
+  - lastProbeTime: "2025-09-03T15:00:50Z"
+    lastTransitionTime: "2025-09-03T15:00:50Z"
+    message: 'Node didn''t have enough capacity: cpu, requested: 1000000, capacity:
+      3500'
+    reason: Infeasible
+    status: "True"
+    type: PodResizePending
+----
+
+Note the following limitations:
+
+* In-place pod resizing is not supported for non-restartable init containers and ephemeral containers.
+* In-place pod resizing is not allowed if the changes violate other pod mutability constraints, such as the pod QoS class.
+* Pods managed by a static `cpuManagerPolicy` or `memoryManagerPolicy` parameter cannot be resized with in-place pod resizing.
+* Pods utilizing swap memory must use the `RestartContainer` policy for memory requests with in-place pod resizing.
+// Above Notes taken from https://kubernetes.io/docs/tasks/configure-pod-container/resize-container-resources/#limitations

modules/nodes-pods-adjust-resources-in-place-configuring.adoc

@@ -0,0 +1,80 @@
+// Module included in the following assemblies:
+//
+// * nodes/pods/nodes-pods-adjust-resources-in-place.adoc
+
+:_mod-docs-content-type: PROCEDURE
+[id="nodes-pods-adjust-resources-in-place-configuring_{context}"]
+= Configuring in-place pod resizing
+
+In-place pod resizing requires that you add a resize policy to a pod specification. 
+
+You cannot add or modify a resize policy in an existing pod, but you can add or edit the policy in the pod's owner object, such as a deployment, if the pod has an owner object. 
+
+.Procedure
+
+. Create a pod spec with a resize policy or add a resize policy to the owner object of an existing pod:
+
+.. Create a YAML file similar to the following example:
++
+[source,yaml]
+----
+apiVersion: v1
+kind: Pod
+metadata:
+  name: resize-pod
+spec:
+# ...
+  containers:
+  - name: pause
+    resizePolicy: <1>
+    - resourceName: cpu
+      restartPolicy: NotRequired
+    - resourceName: memory
+      restartPolicy: RestartContainer
+# ...
+----
+<1> Specifies a resize policy. For CPU and/or memory resources specify one of the following values:
++
+* `NotRequired`: Apply any resource changes without restarting the pod. This is the default when using a resize policy.
+* `RestartContainer`: Apply any resource changes and restart the pod.
+
+.. Create the object by running a command similar to the following:
++
+[source,terminal]
+----
+$ oc create -f <file_name>.yaml
+----
+
+.Verification
+
+* Check that the resize policy is applied by modifying the CPU or memory requests or limits by running a command similar to the following. You must include the `--subresource resize` flag. If the pod has a owner object, such as a deployment, you must edit the owner object. 
++
+[source,terminal]
+----
+$ oc edit pod <pod_name>  --subresource resize
+----
++
+If the policy is applied, the pod responds as expected.
++
+[source,terminal]
+----
+$ oc get pods
+----
++
+If the resize policy is `NotRequired`, the pod is not restarted.
++
+.Example output
+[source,terminal]
+----
+NAME                          READY   STATUS    RESTARTS     AGE
+resize-pod                    1/1     Running   0            5s
+----
++
+If the resize policy is `RestartContainer`, the pod is restarted.
++
+.Example output
+[source,terminal]
+----
+NAME                         READY   STATUS    RESTARTS    AGE
+resize-pod                   1/1     Running   1 (5s ago)  5s
+----

nodes/pods/nodes-pods-adjust-resources-in-place.adoc

@@ -0,0 +1,17 @@
+:_mod-docs-content-type: ASSEMBLY
+:context: nodes-pods-adjust-resources-in-place
+[id="nodes-pods-adjust-resources-in-place"]
+= Adjust pod resource levels without pod disruption
+include::_attributes/common-attributes.adoc[]
+
+toc::[]
+
+You can change the CPU or memory resource requests and limits assigned to a container without re-creating or restarting the pod by using _in-place pod resizing_.
+
+include::modules/nodes-pods-adjust-resources-in-place-about.adoc[leveloffset=+1]
+
+include::modules/nodes-pods-adjust-resources-in-place-configuring.adoc[leveloffset=+1]
+
+[role="_additional-resources"]
+== Additional resources
+* xref:../../nodes/pods/nodes-pods-using.adoc#nodes-pods-understanding-requests-limits_nodes-pods-using-ssy[Understanding resource requests and limits]