digraph cluster {
    node [ shape = "record"]

    subgraph cluster_dc1 {
        label = "dc1";
        cas1
        app1
    }
    subgraph cluster_dc2 {
        label = "dc2";
        cas2
        app2
    }
    app1 -> cas1
    app1 -> cas2
    app2 -> cas1
}

