public static boolean load() {
    try {
      Class.forName(FanOutOneBlockAsyncDFSOutput.class.getName());
      Class.forName(FanOutOneBlockAsyncDFSOutputHelper.class.getName());
      Class.forName(FanOutOneBlockAsyncDFSOutputSaslHelper.class.getName());
      return true;
    } catch (Throwable e) {
      return false;
    }
  }
Test whether we can load the helper classes for async dfs output.
hbase-server/src/main/java/org/apache/hadoop/hbase/wal/AsyncFSWALProvider.java