# OpenAPI Callbacks

You could create an API with a *path operation* that could trigger a request to an *external API* created by someone else (probably the same developer that would be *using* your API).

			}
			ec.queue.Add(key)
			break
		}
	}
}

func (ec *ephemeralController) onPVCDelete(obj interface{}) {
	pvc, ok := obj.(*v1.PersistentVolumeClaim)
	if !ok {
		return
	}

	// Someone deleted a PVC, either intentionally or
	// accidentally. If there is a pod referencing it because of
	// an ephemeral volume, then we should re-create the PVC.
	// The common indexer does some prefiltering for us by

# Handling Errors

There are many situations in which you need to notify an error to a client that is using your API.

This client could be a browser with a frontend, a code from someone else, an IoT device, etc.

You could need to tell the client that:

* The client doesn't have enough privileges for that operation.
* The client doesn't have access to that resource.
* The item the client was trying to access doesn't exist.
* etc.