FuseESB:karaf@root> javax.management.openmbean.KeyAlreadyExistsException: Argument value's index, calculated according to this TabularData instance's tabularType, already refers to a value in this table.
at javax.management.openmbean.TabularDataSupport.checkValueAndIndex(TabularDataSupport.java:871)
at javax.management.openmbean.TabularDataSupport.internalPut(TabularDataSupport.java:331)
at javax.management.openmbean.TabularDataSupport.put(TabularDataSupport.java:323)
at org.apache.karaf.features.management.codec.JmxFeature.getFeatureIdentifierTable(JmxFeature.java:104)
at org.apache.karaf.features.management.codec.JmxFeature.<init>(JmxFeature.java:75)
at org.apache.karaf.features.management.internal.FeaturesServiceMBeanImpl.getFeatures(FeaturesServiceMBeanImpl.java:94)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
at java.lang.reflect.Method.invoke(Method.java:597)
at com.sun.jmx.mbeanserver.StandardMBeanIntrospector.invokeM2(StandardMBeanIntrospector.java:93)
at com.sun.jmx.mbeanserver.StandardMBeanIntrospector.invokeM2(StandardMBeanIntrospector.java:27)
at com.sun.jmx.mbeanserver.MBeanIntrospector.invokeM(MBeanIntrospector.java:208)
at com.sun.jmx.mbeanserver.PerInterface.getAttribute(PerInterface.java:65)
at com.sun.jmx.mbeanserver.MBeanSupport.getAttribute(MBeanSupport.java:216)
at com.sun.jmx.mbeanserver.MBeanSupport.getAttributes(MBeanSupport.java:223)
at javax.management.StandardMBean.getAttributes(StandardMBean.java:376)
at com.sun.jmx.interceptor.DefaultMBeanServerInterceptor.getAttributes(DefaultMBeanServerInterceptor.java:726)
at com.sun.jmx.mbeanserver.JmxMBeanServer.getAttributes(JmxMBeanServer.java:665)
at javax.management.remote.rmi.RMIConnectionImpl.doOperation(RMIConnectionImpl.java:1408)
at javax.management.remote.rmi.RMIConnectionImpl.access$200(RMIConnectionImpl.java:72)
at javax.management.remote.rmi.RMIConnectionImpl$PrivilegedOperation.run(RMIConnectionImpl.java:1265)
at javax.management.remote.rmi.RMIConnectionImpl.doPrivilegedOperation(RMIConnectionImpl.java:1360)
at javax.management.remote.rmi.RMIConnectionImpl.getAttributes(RMIConnectionImpl.java:636)
at sun.reflect.GeneratedMethodAccessor19.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
at java.lang.reflect.Method.invoke(Method.java:597)
at sun.rmi.server.UnicastServerRef.dispatch(UnicastServerRef.java:303)
at sun.rmi.transport.Transport$1.run(Transport.java:159)
at java.security.AccessController.doPrivileged(Native Method)
at sun.rmi.transport.Transport.serviceCall(Transport.java:155)
at sun.rmi.transport.tcp.TCPTransport.handleMessages(TCPTransport.java:535)
at sun.rmi.transport.tcp.TCPTransport$ConnectionHandler.run0(TCPTransport.java:790)
at sun.rmi.transport.tcp.TCPTransport$ConnectionHandler.run(TCPTransport.java:649)
at java.util.concurrent.ThreadPoolExecutor$Worker.runTask(ThreadPoolExecutor.java:886)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:908)
at java.lang.Thread.run(Thread.java:680)

Discovered as the user also has a requirement to retrieve the list of features through JMX, either via jconsole or programmatically.