test.dot

digraph example {
  subgraph {
    rankdir = "LR"
    subgraph clusterfeature1 {
      rankdir = "TB"
      label = "feature1";
      c1 -> c2;
    }

    br_feature1 [shape=rectangle];

    br_feature1 -> c2;
  }

  subgraph {
    rankdir = "LR"
    subgraph clustermaster {
      rankdir = "TB"
      node [style=filled,color=white];
      style=filled;
      color=lightgrey;
      a1 -> a2 -> a3 -> a4 -> a5;
      label = "master";
    }

    br_master [shape=rectangle];

    br_master -> a5;
  }

  a2 -> c1;
  c2 -> a5;




}