sleep when resource in not satisfy. fix #1522 (#1523)

* fix #1515

* sleep when resource in not satisfy. fix #1522

* add sleep 1s for no command

dolphinscheduler-server/src/main/java/org/apache/dolphinscheduler/server/master/runner/MasterSchedulerThread.java

@@ -98,7 +98,11 @@ public class MasterSchedulerThread implements Runnable {
             InterProcessMutex mutex = null;
             try {
 
-                if(OSUtils.checkResource(masterConfig.getMasterMaxCpuloadAvg(), masterConfig.getMasterReservedMemory())){
+                boolean runCheckFlag = OSUtils.checkResource(masterConfig.getMasterMaxCpuloadAvg(), masterConfig.getMasterReservedMemory());
+                if(!runCheckFlag) {
+                    Thread.sleep(Constants.SLEEP_TIME_MILLIS);
+                    continue;
+                }
                 if (zkMasterClient.getZkClient().getState() == CuratorFrameworkState.STARTED) {
 
                     // create distributed lock with the root node path of the lock space as /dolphinscheduler/lock/masters
@@ -124,13 +128,11 @@ public class MasterSchedulerThread implements Runnable {
                             logger.error("scan command error ", e);
                             processDao.moveToErrorCommand(command, e.toString());
                         }
+                    } else{
+                        //indicate that no command ,sleep for 1s
+                        Thread.sleep(Constants.SLEEP_TIME_MILLIS);
                     }
                 }
-                }
-
-                // accessing the command table every SLEEP_TIME_MILLIS milliseconds
-                Thread.sleep(Constants.SLEEP_TIME_MILLIS);
-
             }catch (Exception e){
                 logger.error("master scheduler thread exception : " + e.getMessage(),e);
             }finally{