User-defined rate-limiting key component

[matheuscscp]

After RFC-0008, users have now the ability to define object-level annotations for sending custom metadata to notification providers. This could be used to give users a finer control over how events are rate-limited:

notification-controller/internal/server/event_server.go

Lines 221 to 262 in eddaf14

	// eventKeyFunc generates a unique key for an event based on the provided HTTP
	// request, which can be used to deduplicate events. The key is calculated by
	// concatenating specific event attributes and hashing them using SHA-256.
	// The key is then returned as a hex-encoded string.
	//
	// The event attributes are prefixed with an identifier to avoid collisions
	// between different event attributes.
	func eventKeyFunc(r *http.Request) (string, error) {
	event := r.Context().Value(eventContextKey{}).(*eventv1.Event)
	comps := []string{
	"event",
	"name=" + event.InvolvedObject.Name,
	"namespace=" + event.InvolvedObject.Namespace,
	"kind=" + event.InvolvedObject.Kind,
	"message=" + event.Message,
	}
	objectGroup := event.InvolvedObject.GetObjectKind().GroupVersionKind().Group
	originRevisionKey := fmt.Sprintf("%s/%s", objectGroup, eventv1.MetaOriginRevisionKey)
	originRevision, ok := event.Metadata[originRevisionKey]
	if ok {
	comps = append(comps, "originRevision="+originRevision)
	}
	revisionKey := fmt.Sprintf("%s/%s", objectGroup, eventv1.MetaRevisionKey)
	revision, ok := event.Metadata[revisionKey]
	if ok {
	comps = append(comps, "revision="+revision)
	}
	tokenKey := fmt.Sprintf("%s/%s", objectGroup, eventv1.MetaTokenKey)
	token, ok := event.Metadata[tokenKey]
	if ok {
	comps = append(comps, "token="+token)
	}
	key := strings.Join(comps, "/")
	digest := sha256.Sum256([]byte(key))
	return fmt.Sprintf("%x", digest), nil
	}

We could use the API eventv1.MetaTokenKey, that was created for this purpose. Today, this key is looked up using the object API Group:

notification-controller/internal/server/event_server.go

Lines 253 to 257 in eddaf14

	tokenKey := fmt.Sprintf("%s/%s", objectGroup, eventv1.MetaTokenKey)
	token, ok := event.Metadata[tokenKey]
	if ok {
	comps = append(comps, "token="+token)
	}

We could look up with the new API Group defined in RFC-0008 the same way:

 tokenKey = fmt.Sprintf("%s/%s", eventv1.Group, eventv1.MetaTokenKey) 
 token, ok = event.Metadata[tokenKey] 
 if ok { 
 	comps = append(comps, "token="+token) 
 } 

Then both tokens can be appended to the rate-limiting key components.