feature-blog(ccm): new metric route_sync_total

content/en/blog/_posts/2026/ccm-metric-route-sync-total.md

@@ -0,0 +1,64 @@
+---
+layout: blog
+title: "Kubernetes v1.36: New Metric for Route Sync in the Cloud Controller Manager"
+date: 2026-02-26
+slug: ccm-new-metric-route-sync-total
+author: >
+  [Lukas Metzner](https://github.com/lukasmetzner) (Hetzner)
+---
+
+Kubernetes v1.36 introduces a new alpha counter metric `route_controller_route_sync_total`
+to the Cloud Controller Manager (CCM) route controller implementation at
+[`k8s.io/cloud-provider`](https://github.com/kubernetes/cloud-provider). This metric
+increments each time routes are synced with the cloud provider.
+
+## A/B testing watch-based route reconciliation
+
+This metric was added to help operators validate the
+`CloudControllerManagerWatchBasedRoutesReconciliation` feature gate introduced in
+[Kubernetes v1.35](/blog/2025/12/30/kubernetes-v1-35-watch-based-route-reconciliation-in-ccm/).
+That feature gate switches the route controller from a fixed-interval loop to a watch-based
+approach that only reconciles when nodes actually change. This reduces unnecessary API calls
+to the infrastructure provider, lowering pressure on rate-limited APIs and allowing operators
+to make more efficient use of their available quota.
+
+To A/B test this, compare `route_controller_route_sync_total` with the feature gate
+disabled (default) versus enabled. In clusters where node changes are infrequent, you should
+see a significant drop in the sync rate with the feature gate turned on.
+
+### Example: expected behavior
+
+**With the feature gate disabled** (the default fixed-interval loop), the counter increments
+steadily regardless of whether any node changes occurred:
+
+```
+# After 10 minutes with no node changes
+route_controller_route_sync_total 60
+# After 20 minutes, still no node changes
+route_controller_route_sync_total 120
+```
+
+**With the feature gate enabled** (watch-based reconciliation), the counter only increments
+when nodes are actually added, removed, or updated:
+
+```
+# After 10 minutes with no node changes
+route_controller_route_sync_total 1
+# After 20 minutes, still no node changes — counter unchanged
+route_controller_route_sync_total 1
+# A new node joins the cluster — counter increments
+route_controller_route_sync_total 2
+```
+
+The difference is especially visible in stable clusters where nodes rarely change.
+
+## Where can I give feedback?
+
+If you have feedback, feel free to reach out through any of the following channels:
+- The [#sig-cloud-provider](https://kubernetes.slack.com/messages/sig-cloud-provider) channel on [Kubernetes Slack](https://slack.k8s.io/)
+- The [KEP-5237 issue](https://kep.k8s.io/5237) on GitHub
+- The [SIG Cloud Provider community page](https://github.com/kubernetes/community/tree/05223ecbd2d6f960edb40684dc83d053d49f8b68/sig-cloud-provider) for other communication channels
+
+## How can I learn more?
+
+For more details, refer to [KEP-5237](https://kep.k8s.io/5237).