# Subgraph and cluster (GraphViz)

A subgraph whose name begins with cluster\_ is drawn as a labelled box. That is the mechanism for showing boundaries in Graphviz.

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## What this example shows

* cluster\_ prefixed subgraphs, which draw a boundary.
* Per-cluster styling.
* Edges crossing cluster boundaries, which is usually the interesting part.

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## A worked example

Open it, edit it, or copy the source below.

![Subgraph and cluster (GraphViz)](https://help.gocapable.com/images/att1424064534.svg)

The source, which you can paste into a new diagram and edit:

```
digraph services {
  rankdir=LR;
  compound=true;
  node [shape=box, style=rounded, fontname="Helvetica"];
  edge [fontname="Helvetica", fontsize=10];

  subgraph cluster_public {
    label="Public zone";
    style="rounded,dashed";
    color="#94a3b8";
    gateway [label="API gateway"];
    cdn [label="CDN"];
  }

  subgraph cluster_private {
    label="Private zone";
    style="rounded,dashed";
    color="#94a3b8";
    orders [label="Order service"];
    payments [label="Payment service"];
    inventory [label="Inventory service"];
  }

  subgraph cluster_data {
    label="Data zone";
    style="rounded,dashed";
    color="#94a3b8";
    pg [label="Postgres", shape=cylinder];
    redis [label="Redis", shape=cylinder];
  }

  cdn -> gateway;
  gateway -> orders;
  orders -> payments [label="sync"];
  orders -> inventory [label="async", style=dashed];
  orders -> pg;
  payments -> pg;
  inventory -> redis;
}
```

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## Making it your own

* The cluster\_ prefix is required. A subgraph without it draws no box.
* compound=true lets you draw edges to a cluster rather than to a node inside it.
* Style the clusters consistently, or the boundaries stop reading as boundaries.

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## Related

[Record and struct (GraphViz)Nodes with fields, and edges to specific fields.](https://help.gocapable.com/diagrams/record-and-struct-graphviz.html)

[Undirected graph (GraphViz)No arrows, because the relationship is symmetric.](https://help.gocapable.com/diagrams/undirected-graph-graphviz.html)

[GraphViz examplesBack to the rest of these examples.](https://help.gocapable.com/diagrams/graphviz-examples.html)

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_Give it the edges. It does the rest._