feat(blog): feature blog for watch based routes reconciliation (#52973)

* feat(blog): feature blog for watch based routes reconciliation Co-authored-by: Michael McCune <msm@opbstudios.com> Co-authored-by: Tim Bannister <193443691+lmktfy@users.noreply.github.com> Co-authored-by: Graziano Casto <graziano.casto@outlook.com> * docs: spelling and punctuation correction Co-authored-by: Susan Sica <90214772+Serenity611@users.noreply.github.com> * docs: apply review suggestions Co-authored-by: Graziano Casto <graziano.casto@outlook.com> --------- Co-authored-by: Michael McCune <msm@opbstudios.com> Co-authored-by: Tim Bannister <193443691+lmktfy@users.noreply.github.com> Co-authored-by: Graziano Casto <graziano.casto@outlook.com> Co-authored-by: Susan Sica <90214772+Serenity611@users.noreply.github.com>

Author: 5 people

content/en/blog/_posts/2025-10-27-watch-based-route-reconciliation-in-ccm.md

@@ -0,0 +1,39 @@
+---
+layout: blog
+title: "Kubernetes v1.35: Watch Based Route Reconciliation in the Cloud Controller Manager"
+date: 2025-10-27T08:30:00-07:00
+draft: true
+slug: watch-based-route-reconciliation-in-ccm
+author: >
+ [Lukas Metzner](https://github.com/lukasmetzner) (Hetzner)
+---
+
+Up to and including Kubernetes v1.34, the route controller in Cloud Controller Manager (CCM)
+implementations built using the [k8s.io/cloud-provider](https://github.com/kubernetes/cloud-provider) library reconciles
+routes at a fixed interval. This causes unnecessary API requests to the cloud provider when
+there are no changes to routes. Other controllers implemented through the same library already
+use watch-based mechanisms, leveraging informers to avoid unnecessary API calls. A new feature gate
+is being introduced in v1.35 to allow changing the behavior of the route controller to use watch-based informers.
+
+## What's new?
+
+The feature gate `CloudControllerManagerWatchBasedRoutesReconciliation` has been
+introduced to [k8s.io/cloud-provider](https://github.com/kubernetes/cloud-provider) in alpha stage by [SIG Cloud Provider](https://github.com/kubernetes/community/blob/master/sig-cloud-provider/README.md).
+To enable this feature you can use `--feature-gate=CloudControllerManagerWatchBasedRoutesReconciliation=true`
+in the CCM implementation you are using.
+
+## About the feature gate
+
+This feature gate will trigger the route reconciliation loop whenever a node is
+added, deleted, or the fields `.spec.podCIDRs` or `.status.addresses` are updated.
+
+An additional reconcile is performed in a random interval between 12h and 24h,
+which is chosen at the controller's start time.
+
+This feature gate does not modify the logic within the reconciliation loop.
+Therefore, users of a CCM implementation should not experience significant
+changes to their existing route configurations.
+
+## How can I learn more?
+
+For more details, refer to the [KEP-5237](https://kep.k8s.io/5237).