first PR (#4699)

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

@@ -52,7 +52,9 @@ public class MasterTaskExecThread extends MasterBaseTaskExecThread {
      */
     private TaskInstanceCacheManager taskInstanceCacheManager;
 
-
+    /**
+     *  netty executor manager
+     */
     private NettyExecutorManager nettyExecutorManager;