void registerContainer(ContainerId containerId, String hostname, int port) {
      if (LOG.isDebugEnabled()) {
        LOG.debug("Registering " + containerId + " for node: " + hostname + ":" + port);
      }
      containerToNodeMap.putIfAbsent(containerId, LlapNodeId.getInstance(hostname, port));
      // nodeMap registration is not required, since there's no taskId association.
    }
Track the association between known containers and taskAttempts, along with the nodes they are assigned to.
llap-tez/src/java/org/apache/hadoop/hive/llap/tezplugins/LlapTaskCommunicator.java