synchronized LlapTaskUmbilicalProtocol getUmbilical() throws IOException, InterruptedException {
      if (umbilical == null) {
        umbilical = createUmbilical(this);
      }
      return umbilical;
    }
Responsible for communicating with various AMs.
llap-server/src/java/org/apache/hadoop/hive/llap/daemon/impl/AMReporter.java