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  • When and how to map a MBean to a SNMP table?
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Generally, every MBean that is not a singleton, should be mapped (or modeled) to (as) a SNMP table. MBeans that contain lists of other MBeans or Java objects should be mapped to several SNMP tables that share a common base index (i.e., the index of the master MBean/table).

The following steps describe how a MBean can be descriptively mapped to a table:

  1. First of all, you need a JMXTableSupport instance which is registered with the MBean server:

    final MBeanServerConnection server =
        ManagementFactory.getPlatformMBeanServer();
    
    final MBeanAttributeMOTableSupport tableSupport =
        new MBeanAttributeMOTableSupport(server);
    
  2. Next you need to define how the index of the SNMP table is mapped from MBean data or autogenerated. The mapping is done bidirectional by mapping a MBean to a key uniquely identifying the MBean and an Index (OID) uniquely defining the SNMP table row(MOTableRow). The JMXIndexSupport knows about Key and Index and thus provides the mapping. 

    tableSupport.add(oidJvmThreadInstanceEntry,
              new MBeanAttributeMOTableInfo(onameJvmThreading,
    
    // The key provider retrieves all available keys (thus all available MBean instances:
              new MBeanInvokationKeyProvider(onameJvmThreading,
                                             new TypedAttribute("AllThreadIds", long.class),
                                             "getThreadInfo", true),
    ...
              new String[] { "ThreadId" },
    
    // The JMX index support maps from rowIdentidier (= Key) to MBean objectname and ...
              new JMXIndexSupport() {
            public ObjectName mapToRowMBean(Object rowIdentifier) {
              return null;
            }
    
    // from rowIdentfier to index OID and ...
            public OID mapToIndex(Object rowIdentifier) {
              Long l = (Long)rowIdentifier;
              return OctetString.fromHexString(Long.toHexString(l)).toSubIndex(true);
            }
    
    // maps native row ID (key used by MBean) or index to rowIdentifier ...
            public Object getRowIdentifier(Object nativeRowId, int nativeIndex) {
              return nativeRowId;
            }
    
    // maps index OID to rowIdentifier (= Key)
            public Object mapToRowIdentifier(OID rowIndex) {
              if (rowIndex == null) {
                return null;
              }
              OctetString os = new OctetString();
              os.fromSubIndex(rowIndex, true);
              String hexString = os.toHexString();
              return Long.parseLong(hexString, 16);
            }
          }));
    
    
  3. Next, each column of the SNMP table needs to be mapped to a MBean attribute or action:

    tableSupport.add(oidJvmThreadInstanceEntry,
              new MBeanAttributeMOTableInfo(onameJvmThreading,
              new MBeanInvokationKeyProvider(onameJvmThreading,
                                             new TypedAttribute("AllThreadIds", long.class),
                                             "getThreadInfo", true),
              new TypedAttribute[] {
              new TypedCompositeDataAttribute(new TypedAttribute("threadId", Long.class)),
              new CombinedBitsType(new TypedAttribute[] {
                                   new EnumBitsType("threadState", Thread.State.class, Thread.State.values(), 3),
                                   new BooleanBitsType("inNative", 1),
                                   new BooleanBitsType("suspended", 2)}),
              new TypedCompositeDataAttribute(new TypedAttribute("blockedCount", Long.class)),
              new TypedCompositeDataAttribute(new TypedAttribute("blockedTime", Long.class)),
              new TypedCompositeDataAttribute(new TypedAttribute("waitedCount", Long.class)),
              new TypedCompositeDataAttribute(new TypedAttribute("waitedTime", Long.class)),
              new MBeanProxyType(server, onameJvmThreading, Long.class,
                                 "getThreadUserTime",
                                 new TypedCompositeDataAttribute(new TypedAttribute("threadId", long.class))) {
                public Object transformFromNative(Object nativeValue, ObjectName objectName) {
                  Long result = (Long) super.transformFromNative(nativeValue, objectName);
                  if ((result == null) || (result < 0)) {
                    return 0L;
                  }
                  return result;
                }
              },
              new TypedCompositeDataAttribute(new TypedAttribute("threadName", String.class)),
              new TypedCompositeDataAttribute(new TypedAttribute("lockOwnerName", String.class)),
              new TypedCompositeDataAttribute(new TypedAttribute("lockOwnerId", Long.class)) {
                public Object transformFromNative(Object nativeValue, ObjectName objectName) {
                  Long result = (Long)super.transformFromNative(nativeValue, objectName);
                  if ((result == null) || (result < 0)) {
                    return "0.0";
                  }
                  OID rowPointer = new OID(JvmManagementMib.oidJvmThreadInstanceEntry);
                  rowPointer.append(JvmManagementMib.colJvmThreadInstId);
                  String index = Long.toHexString(result);
                  OctetString os = OctetString.fromHexString(index);
                  rowPointer.append(os.toSubIndex(true));
                  return rowPointer.toString();
                }
              }},
              new String[] { "ThreadId" },
              new JMXIndexSupport() {
            public ObjectName mapToRowMBean(Object rowIdentifier) {
              return null;
            }
    
            public Object getRowIdentifier(Object nativeRowId, int nativeIndex) {
              return nativeRowId;
            }
    
            public OID mapToIndex(Object rowIdentifier) {
              Long l = (Long)rowIdentifier;
              return OctetString.fromHexString(Long.toHexString(l)).toSubIndex(true);
            }
    
            public Object mapToRowIdentifier(OID rowIndex) {
              if (rowIndex == null) {
                return null;
              }
              OctetString os = new OctetString();
              os.fromSubIndex(rowIndex, true);
              String hexString = os.toHexString();
              return Long.parseLong(hexString, 16);
            }
    }));
    
  4. Finally, the table model of the MOTable has been set to the JMXTableModel bound to the table support and table OID created in the previous steps:

    JMXTableModel jvmMemMgrPoolRelEntryModel =
        JMXTableModel.getDefaultInstance(oidJvmMemMgrPoolRelEntry,
                              tableSupport,
                              super.getJvmMemMgrPoolRelEntry().getColumns());
    ((MOTableJMX)super.getJvmMemMgrPoolRelEntry()).
        setModel(jvmMemMgrPoolRelEntryModel);
    
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