HDFS-16824. add synchronized.

Author: slfan1989

hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/tools/DFSAdmin.java

@@ -2068,51 +2068,51 @@ int getReconfigurationStatus(final String nodeType, final String address, final
       errMsg = String.format("Node [%s] reloading configuration: %s.", address,
           e.toString());
     }
-
-    if (errMsg != null) {
-      err.println(errMsg);
-      return 1;
-    } else {
-      out.print(outMsg);
-    }
-
-    if (status != null) {
-      if (!status.hasTask()) {
-        out.println("no task was found.");
-        return 0;
-      }
-      out.print("started at " + new Date(status.getStartTime()));
-      if (!status.stopped()) {
-        out.println(" and is still running.");
-        return 0;
+    synchronized (this) {
+      if (errMsg != null) {
+        err.println(errMsg);
+        return 1;
+      } else {
+        out.print(outMsg);
       }
 
-      out.println(" and finished at "
-          + new Date(status.getEndTime()).toString() + ".");
-      if (status.getStatus() == null) {
-        // Nothing to report.
-        return 0;
-      }
-      for (Map.Entry<PropertyChange, Optional<String>> result : status
-          .getStatus().entrySet()) {
-        if (!result.getValue().isPresent()) {
-          out.printf(
-              "SUCCESS: Changed property %s%n\tFrom: \"%s\"%n\tTo: \"%s\"%n",
-              result.getKey().prop, result.getKey().oldVal,
-              result.getKey().newVal);
-        } else {
-          final String errorMsg = result.getValue().get();
-          out.printf(
-              "FAILED: Change property %s%n\tFrom: \"%s\"%n\tTo: \"%s\"%n",
-              result.getKey().prop, result.getKey().oldVal,
-              result.getKey().newVal);
-          out.println("\tError: " + errorMsg + ".");
+      if (status != null) {
+        if (!status.hasTask()) {
+          out.println("no task was found.");
+          return 0;
         }
+        out.print("started at " + new Date(status.getStartTime()));
+        if (!status.stopped()) {
+          out.println(" and is still running.");
+          return 0;
+        }
+
+        out.println(" and finished at "
+                + new Date(status.getEndTime()).toString() + ".");
+        if (status.getStatus() == null) {
+          // Nothing to report.
+          return 0;
+        }
+        for (Map.Entry<PropertyChange, Optional<String>> result : status
+                .getStatus().entrySet()) {
+          if (!result.getValue().isPresent()) {
+            out.printf(
+                    "SUCCESS: Changed property %s%n\tFrom: \"%s\"%n\tTo: \"%s\"%n",
+                    result.getKey().prop, result.getKey().oldVal,
+                    result.getKey().newVal);
+          } else {
+            final String errorMsg = result.getValue().get();
+            out.printf(
+                    "FAILED: Change property %s%n\tFrom: \"%s\"%n\tTo: \"%s\"%n",
+                    result.getKey().prop, result.getKey().oldVal,
+                    result.getKey().newVal);
+            out.println("\tError: " + errorMsg + ".");
+          }
+        }
+      } else {
+        return 1;
       }
-    } else {
-      return 1;
     }
-
     return 0;
   }