protected final synchronized void setupClusterConnection() throws IOException {
    if (asyncClusterConnection == null) {
      InetSocketAddress localAddress =
        new InetSocketAddress(rpcServices.getSocketAddress().getAddress(), 0);
      User user = userProvider.getCurrent();
      asyncClusterConnection =
        ClusterConnectionFactory.createAsyncClusterConnection(this, conf, localAddress, user);
    }
  }
Setup our cluster connection if not already initialized.
hbase-server/src/main/java/org/apache/hadoop/hbase/HBaseServerBase.java