Server-Side Apply

Tanka supports server-side apply, which requires at least Kubernetes 1.16+, and was promoted to stable status in 1.22.

To enable server-side diff in tanka, add the following field to spec.json:

{
  "spec": {
+    "applyStrategy": "server",
  }
}

This also has the effect of changing the default diff strategy to server, but this can be overridden via command line flags or spec.json.

While server-side apply doesn't have any effect on the resources being applied and is intended to be a general in-place upgrade to client-side apply, there are differences in how fields are managed that can make converting existing cluster resources a non-trival change.

Identifying and fixing these changes are beyond the scope of this guide, but many can be found before an apply by using the validate or server diff strategy.

Field conflicts

As part of the changes, you may encounter error messages which recommend the use of the --force-conflicts flag. Using tk apply --force in server-side mode will enable that flag for kubectl instead of kubectl --force, which no longer has any effect in server-side mode.