HADOOP-8027. Visiting /jmx on the daemon web interfaces may print unnecessary error in logs. Contributed by Aaron T. Myers.

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-0.23@1241308 13f79535-47bb-0310-9956-ffa450edef68

hadoop-common-project/hadoop-common/CHANGES.txt

@@ -90,11 +90,14 @@ Release 0.23.1 - Unreleased
     HADOOP-8002. SecurityUtil acquired token message should be a debug rather than info.
     (Arpit Gupta via mahadev)
 
-   HADOOP-8009. Create hadoop-client and hadoop-minicluster artifacts for downstream 
-   projects. (tucu)
+    HADOOP-8009. Create hadoop-client and hadoop-minicluster artifacts for downstream 
+    projects. (tucu)
 
     HADOOP-7470. Move up to Jackson 1.8.8.  (Enis Soztutar via szetszwo)
 
+    HADOOP-8027. Visiting /jmx on the daemon web interfaces may print
+    unnecessary error in logs. (atm)
+
   OPTIMIZATIONS
 
     HADOOP-7761. Improve the performance of raw comparisons. (todd)

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

@@ -34,6 +34,7 @@ import javax.management.MBeanServer;
 import javax.management.MalformedObjectNameException;
 import javax.management.ObjectName;
 import javax.management.ReflectionException;
+import javax.management.RuntimeMBeanException;
 import javax.management.openmbean.CompositeData;
 import javax.management.openmbean.CompositeType;
 import javax.management.openmbean.TabularData;
@@ -312,6 +313,15 @@ public class JMXJsonServlet extends HttpServlet {
     Object value = null;
     try {
       value = mBeanServer.getAttribute(oname, attName);
+    } catch (RuntimeMBeanException e) {
+      // UnsupportedOperationExceptions happen in the normal course of business,
+      // so no need to log them as errors all the time.
+      if (e.getCause() instanceof UnsupportedOperationException) {
+        LOG.debug("getting attribute "+attName+" of "+oname+" threw an exception", e);
+      } else {
+        LOG.error("getting attribute "+attName+" of "+oname+" threw an exception", e);
+      }
+      return;
     } catch (AttributeNotFoundException e) {
       //Ignored the attribute was not found, which should never happen because the bean
       //just told us that it has this attribute, but if this happens just don't output