Include self correction on empty batch and avoid removing pending runners when cluster is busy (#3426)

cmd/ghalistener/listener/listener.go

@@ -164,6 +164,11 @@ func (l *Listener) Listen(ctx context.Context, handler Handler) error {
 		}
 
 		if msg == nil {
+			_, err := handler.HandleDesiredRunnerCount(ctx, 0, 0)
+			if err != nil {
+				return fmt.Errorf("handling nil message failed: %w", err)
+			}
+
 			continue
 		}
 

cmd/ghalistener/worker/worker.go

@@ -177,12 +177,12 @@ func (w *Worker) HandleDesiredRunnerCount(ctx context.Context, count int, jobsCo
 		"jobsCompleted", jobsCompleted,
 	}
 
-	if w.lastPatch == targetRunnerCount && jobsCompleted == 0 {
-		w.logger.Info("Skipping patch", logValues...)
-		return targetRunnerCount, nil
+	if count == 0 && jobsCompleted == 0 {
+		w.lastPatchID = 0
+	} else {
+		w.lastPatchID++
 	}
 
-	w.lastPatchID++
 	w.lastPatch = targetRunnerCount
 
 	original, err := json.Marshal(