private boolean add(SimpleServerRpcConnection connection) {
      boolean added = connections.add(connection);
      if (added) {
        count.getAndIncrement();
      }
      return added;
    }
The number of open RPC conections
@return the number of open rpc connections
hbase-server/src/main/java/org/apache/hadoop/hbase/ipc/SimpleRpcServer.java