Control concurrent reconcile per namespace

[a7i]

controller-runtime provides the ability to control the MaxConcurrentReconciles

controller-runtime/pkg/config/controller.go

Lines 47 to 48 in 252af64

	// MaxConcurrentReconciles is the maximum number of concurrent Reconciles which can be run. Defaults to 1.
	MaxConcurrentReconciles int

This works great to control the concurrency limit at a global level, but I'm looking to limit it per namespace. In my use-case, I am reconciling pods in a particular order and the order only matters within a namespace and for a large cluster it's inefficient to have a global limit of 1.

	return ctrl.NewControllerManagedBy(mgr).
		Named(ControllerName).
		WithOptions(controller.Options{MaxConcurrentReconciles: 1}).
		For(&corev1.Pod{}, builder.WithPredicates(predicate.NewPredicateFuncs(func(object client.Object) bool {
			pod := object.(*corev1.Pod)

			if err := shouldReconcile(pod); err != nil {
				mgr.GetLogger().V(4).Info("skipping pod reconciliation: %s", err.Error())
				return false
			}

			return true
		}))).
		Complete(r)

I realize that not all resources are namespaced so we have to be aware of that in the api.

[alvaroaleman]

You can implement this as a reconciler wrapper, I don't think this is a common-enough use-case to warrant anything in controller-runtime.

[sbueringer]

I think it would also require large-scale changes to / refactoring of CR

[a7i]

Would you elaborate on how one can do that? An example would be great!