feat(blog): Add new blog featuring adoption of in-place Pod resource updates

website/blog/2026/05/05-19-in-place-pod-resource-updates.md

@@ -0,0 +1,109 @@
+---
+title: Adoption of In-Place Pod Resource Updates in Gardener
+linkTitle: Adoption of In-Place Pod Resource Updates in Gardener
+newsSubtitle: May 19, 2026
+publishdate: 2026-05-19
+authors:
+- avatar: https://avatars.githubusercontent.com/vitanovs
+  login: vitanovs
+  name: Stoyan Vitanov
+aliases: [/blog/2026/05/19/in-place-pod-resource-updates]
+tags:
+- autoscaling
+- vpa
+---
+
+As Kubernetes workloads evolve, the need for dynamic resource adjustments becomes increasingly critical. Traditional `Pod` resource updates require `Pod` recreation, leading to increased operational costs and potential service disruptions.
+To address this shortcoming, Kubernetes introduced a new way of updating `Pod` resources _in-place_, without the need to _evict_ workloads in order to apply the configuration change. With the [v1.27](https://kubernetes.io/releases/1.27/) release, a new `resize` subresource got introduced to the `Pod`'s API, acting as an interface to the underlying CRI implementations that manage the _cgroups_ settings.
+
+## What are the key benefits of _in-place_ Pod resource updates?
+
+Having the ability to bypass the rollout process when updating `Pod` resources drastically improves the scaling efficiency. Eliminating the overhead of `Pod` scheduling and application initialization is among the primary benefits of the new _update_ mechanism. The following points summarize the key factors when considering using _in-place_ updates:
+
+- __Zero-downtime scaling__: Resources are adjusted without `Pod` recreation or service interruption
+- __Reduced scheduling overhead__: No need to re-schedule `Pod`s across the cluster
+- __Reduced initialization overhead__: Applications __do not__ go through full initialization all over again
+- __Preserved `Pod` identity__: `Pod` names, IPs, and volumes remain unchanged
+- __Improved resource efficiency__: More granular and responsive resource optimization
+
+To read more about the feature, refer to the official [documentation](https://kubernetes.io/blog/2025/12/19/kubernetes-v1-35-in-place-pod-resize-ga/).
+
+## How does Gardener utilize the new _update_ mechanism?
+
+Gardener relies heavily on the [Vertical Pod Autoscaler](https://github.com/kubernetes/autoscaler) to advance the resource usage optimization and keep the _out-of-the-box_ components running as efficiently as possible. With the [v1.4.0](https://github.com/kubernetes/autoscaler/releases/tag/vertical-pod-autoscaler-1.4.0) release, Vertical Pod Autoscaler introduced the ability to configure a new `.spec.updatePolicy.updateMode` for the `VerticalPodAutoscaler` resources:
+
+```yaml
+apiVersion: autoscaling.k8s.io/v1
+kind: VerticalPodAutoscaler
+metadata:
+  name: demo-vpa
+spec:
+  targetRef:
+    apiVersion: "apps/v1"
+    kind:       Deployment
+    name:       demo
+  updatePolicy:
+    updateMode: "InPlaceOrRecreate"
+```
+
+effectively performing _in-place_ resource updates and _falling back_ to _eviction_ in case of failure. Adopting this release created the opportunity to leverage the new _update_ mechanism, and with Gardener [v1.137](https://github.com/gardener/gardener/releases/tag/v1.137.0), a new automatic migration mechanism was introduced.
+
+Historically, `VerticalPodAutoscaler` resources, created for the different Gardener components, were configured to use _update mode_ `Auto` as it was the default option that mimics the behavior of `Recreate` - _evicting_ `Pod`s to apply newly [calculated resource recommendations](https://github.com/kubernetes/autoscaler/blob/master/vertical-pod-autoscaler/docs/components.md#implementation-of-the-recommender). The subsequent Vertical Pod Autoscaler [v1.5.0](https://github.com/kubernetes/autoscaler/releases/tag/vertical-pod-autoscaler-1.5.0) release deprecated the `Auto` _update mode_, leaving only two viable options for continuous scaling: `Recreate` and `InPlaceOrRecreate`. The following graph illustrates the _flow_ of `Pod` resource updates used in Gardener:
+
+```mermaid
+graph LR
+    A[VPA Recommender] -->|new recommendation| B[VPA Updater]
+    B -->|PATCH /resize subresource| C[API Server]
+    C -->|sends update request| D[Kubelet]
+    D -->|sends update request| E[CRI Runtime]
+    E -->|updates cgroups| F[Running Container]
+    F -->|updates status| D
+    D -->|updates Pod status| C
+```
+
+The _key_ functionality behind this improved resource management is Linux [cgroups](https://www.man7.org/linux/man-pages/man7/cgroups.7.html), which are responsible for grouping processes and limiting the host resources they can utilize.
+
+### How are `VerticalPodAutoscaler` resources configured?
+
+Like any cluster-wide configuration change, migrating the `VerticalPodAutoscaler` resources' _update mode_ presented a unique challenge that solved this by leveraging the [Gardener Resource Manager](https://github.com/gardener/gardener/blob/master/docs/concepts/resource-manager.md) and its extensible architecture.
+
+We developed a dedicated `MutatingWebhook` that automatically filters relevant `VerticalPodAutoscaler` resources and applies the _update mode_ change, making the migration seamless. The webhook is deployed through the `VPAInPlaceUpdates` _feature gate_ (available in both `gardenlet` and [Gardener Operator](https://github.com/gardener/gardener/blob/master/docs/concepts/operator.md)).
+We also built a _rollback_ mechanism to ensure safety—if the feature gate is disabled, migration scripts automatically revert the _update mode_ changes during `gardenlet` or `operator` initialization. These changes have been available since Gardener [v1.137](https://github.com/gardener/gardener/releases/tag/v1.137.0), making _in-place_ update mode adoption fully operational and ready for production use.
+
+For detailed information on [usage](https://github.com/gardener/gardener/blob/master/docs/usage/autoscaling/in-place-resource-updates.md) and [enablement](https://github.com/gardener/gardener/blob/master/docs/operations/enabling-in-place-resource-updates.md), refer to the official documentation.
+
+## Monitoring
+
+Performing configuration migrations can become an exhausting task without a convenient dashboard to evaluate the process state. For this reason, as part of the effort to support _in-place_ Pod resource updates, we introduced a brand new _dashboard_ for the `vpa-updater` component.
+
+![VPA Updater Dashboard Overview](./images/in-place-pod-resource-updates/vpa-updater-dashboard-overview.png)
+
+With sections covering `VerticalPodAutoscaler` resource overviews (segregated by _update mode_) and panels displaying success rates per resource, the new dashboard can be used for both monitoring and generating status reports on applied resource recommendations.
+
+## References
+
+The following list of references can be used for further reading and technical deep dives into the topic.
+
+### Kubernetes Documentation
+
+- [In-Place Pod Resize (GA in v1.35)](https://kubernetes.io/blog/2025/12/19/kubernetes-v1-35-in-place-pod-resize-ga/)
+- [Resize Container Resources](https://kubernetes.io/docs/tasks/configure-pod-container/resize-container-resources/)
+- [Pod v1 API Reference - resize subresource](https://kubernetes.io/docs/reference/kubernetes-api/workload-resources/pod-v1/#operations-pod-v1-resize)
+
+### Vertical Pod Autoscaler
+
+- [VPA v1.4.0 Release Notes](https://github.com/kubernetes/autoscaler/releases/tag/vertical-pod-autoscaler-1.4.0) (introduced InPlaceOrRecreate)
+- [VPA v1.5.0 Release Notes](https://github.com/kubernetes/autoscaler/releases/tag/vertical-pod-autoscaler-1.5.0) (deprecated Auto mode)
+- [VPA In-Place Updates Documentation](https://github.com/kubernetes/autoscaler/blob/master/vertical-pod-autoscaler/docs/features.md#in-place-updates-inplaceorrecreate)
+
+### Gardener Documentation
+
+- [Usage: In-Place Resource Updates](https://github.com/gardener/gardener/blob/master/docs/usage/autoscaling/in-place-resource-updates.md)
+- [Operations: Enabling In-Place Resource Updates](https://github.com/gardener/gardener/blob/master/docs/operations/enabling-in-place-resource-updates.md)
+- [Gardener Resource Manager](https://github.com/gardener/gardener/blob/master/docs/concepts/resource-manager.md)
+- [Gardener v1.137.0 Release Notes](https://github.com/gardener/gardener/releases/tag/v1.137.0)
+
+### Technical Deep Dives
+
+- [Linux cgroups v2](https://www.kernel.org/doc/html/latest/admin-guide/cgroup-v2.html)
+- [CRI (Container Runtime Interface) Specification](https://github.com/kubernetes/cri-api)