code: @Validate
      public void start() {
          Configuration conf = configuration.getConfiguration("pools");
  
          createExecutor(ManagedExecutorService.SYSTEM,
                  conf != null ? conf.getConfiguration("executors." + ManagedExecutorService.SYSTEM) : null);
          createScheduler(ManagedScheduledExecutorService.SYSTEM,
                  conf != null ? conf.getConfiguration("schedulers." + ManagedScheduledExecutorService.SYSTEM) : null);
  
          if (conf != null) {
              createOtherExecutors(conf.getConfiguration("executors"));
              createOtherSchedulers(conf.getConfiguration("schedulers"));
          }
      }
docs: Creates the system executors and the others specified executors.