runservice scheduler: choose scheduler only if it has capacity

internal/services/config/config.go

@@ -182,6 +182,9 @@ var defaultConfig = Config{
 	RunServiceScheduler: RunServiceScheduler{
 		RunCacheExpireInterval: 7 * 24 * time.Hour,
 	},
+	RunServiceExecutor: RunServiceExecutor{
+		ActiveTasksLimit: 2,
+	},
 }
 
 func Parse(configFile string) (*Config, error) {

internal/services/runservice/scheduler/scheduler.go

@@ -293,6 +293,11 @@ func (s *Scheduler) chooseExecutor(ctx context.Context, rct *types.RunConfigTask
 			if e.Labels["arch"] != string(rct.Runtime.Arch) {
 				continue
 			}
+			if e.ActiveTasksLimit != 0 {
+				if e.ActiveTasks >= e.ActiveTasksLimit {
+					continue
+				}
+			}
 		}
 
 		return e, nil