private String getErrorMessage(Throwable t) {
      StringBuilder sb = new StringBuilder(t.getMessage());
      while (t.getCause() != null) {
        sb.append(t.getCause().getMessage());
        t = t.getCause();
      }
      return sb.toString();
    }
Unregister a specific dag

This method and registerDag must be synchronized externally to prevent races in shuffle token registration/unregistration

@param dir
@param applicationIdString
@param dagIdentifier
llap-server/src/java/org/apache/hadoop/hive/llap/shufflehandler/ShuffleHandler.java