private boolean isSslError(Throwable cause) {
    Throwable error = cause;
    do {
      if (error instanceof SSLException) {
        return true;
      }
      error = error.getCause();
    } while (error != null);
    return false;
  }
We will expose the connection to upper layer before initialized, so we need to buffer the calls
passed in and write them out once the connection is established.
hbase-client/src/main/java/org/apache/hadoop/hbase/ipc/BufferCallBeforeInitHandler.java