HADOOP-15942. Change the logging level form DEBUG to ERROR for RuntimeErrorException in JMXJsonServlet. Contributed by Anuhan Torgonshar.

hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/jmx/JMXJsonServlet.java

@@ -348,7 +348,8 @@ public class JMXJsonServlet extends HttpServlet {
     } catch (RuntimeErrorException e) {
       // RuntimeErrorException happens when an unexpected failure occurs in getAttribute
       // for example https://issues.apache.org/jira/browse/DAEMON-120
-      LOG.debug("getting attribute "+attName+" of "+oname+" threw an exception", e);
+      LOG.error("getting attribute {} of {} threw an exception",
+          attName, oname, e);
       return;
     } catch (AttributeNotFoundException e) {
       //Ignored the attribute was not found, which should never happen because the bean