code: private ClientSocketStats getOrCreateNodeStats(SocketDestination destination) {
          if(destination == null) {
              return null;
          }
          ClientSocketStats stats = statsMap.get(destination);
          if(stats == null) {
              ClientSocketStats socketStats = new ClientSocketStats(this,
                                                                    destination,
                                                                    pool,
                                                                    identifierString);
              // The idea here is to avoid registering the bean multiple times.
              // This can happen when
              // two threads, both read the stats object as null (three lines
              // above) and then try to
              // populate the map with their own socketStats object. putifabsent
              // returns the existing
              // value if the key exists or returns null. The thread that does the
              // first put will
              // get a null return vale. That thread will then go on to get the
              // stats object and register
              // the bean. All the other threads will have their stats object
              // populated by the return
              // value of the putIfAbsent call that will return the existing value
              // in the map.
              stats = statsMap.putIfAbsent(destination, socketStats);
              if(stats == null) {
                  stats = socketStats;
                  JmxUtils.registerMbean(new ClientSocketStatsJmx(stats),
                                         JmxUtils.createObjectName(JmxUtils.getPackageName(ClientRequestExecutor.class),
                                                                   "stats_"
                                                                           + destination.toString()
                                                                                        .replace(':',
                                                                                                 '_')
                                                                           + identifierString));
              }
          }
          return stats;
      }
docs: /* get per node stats, create one if not exist