NodeGraph: Add docs (#30504)

* Add draft docs

* Update node-graph.md

* Update whats-new-in-v7-4.md

* Update images and add x-ray link

* Update docs/sources/panels/visualizations/node-graph.md

* Update docs/sources/panels/visualizations/node-graph.md

* Update node-graph.md

* Add definition of node and edge

* Update docs/sources/panels/visualizations/node-graph.md

* Update docs/sources/panels/visualizations/node-graph.md

Co-authored-by: Diana Payton <52059945+oddlittlebird@users.noreply.github.com>

docs/sources/panels/visualizations/node-graph.md

++++
+title = "Node graph"
+keywords = ["grafana", "dashboard", "documentation", "panels", "node graph", "directed graph"]
+weight = 850
++++
+
+# Node graph panel
+
+> **Note:** This panel is currently in beta. Expect changes in future releases.
+
+The _Node graph_ can visualize directed graphs or networks. It uses directed force layout to effectively position the nodes so it can help with displaying complex infrastructure maps, hierarchies or execution diagrams.
+
+![Node graph panel](/img/docs/node-graph/node-graph-7-4.png "Node graph")
+
+## Data requirements
+
+The Node graph panel requires specific shape of the data to be able to display it's nodes and edges. This means not every data source or query can be visualized in this panel. If you want to use this as a data source developer see the section about data API.  
+
+The Node graph visualization consists of _nodes_ and _edges_.
+
+- A _node_ is displayed as a circle. A node might represent an application, a service, or anything else that is relevant from an application perspective.
+- An _edge_ is displayed as a line that connects two nodes. The connection might be a request, an execution, or some other relationship between the two nodes.
+
+Both nodes and edges can have associated metadata or statistics. The data source defines what information and values is shown, so different data sources can show different type of values or not show some values.
+
+### Nodes
+
+> **Note:** At this moment node graph can show only 1,500 nodes. If this limit is crossed a warning will be visible in upper right corner.
+
+Usually, nodes show two statistical values inside the node and two identifiers just below the node, usually name and type. Nodes can also show another set of values as a color circle around the node, with sections of different color represents different values that should add up to 1.
+
+For example you can have percentage of errors represented by red portion of the circle. Additional details can be displayed in a context menu when which is displayed when you click on the node. There also can be additional links in the context menu that can target either other parts of Grafana or any external link.
+
+![Node graph navigation](/img/docs/node-graph/node-graph-navigation-7-4.gif "Node graph navigation")
+
+### Edges
+
+Edges can also show statistics when you hover over the edge. Similar to nodes, you can open a context menu with additional details and links by clicking on the edge.
+
+The first data source supporting this visualization is X-Ray data source for it's Service map feature. For more information, refer to the [X-Ray plugin documentation](https://grafana.com/grafana/plugins/grafana-x-ray-datasource).
+
+## Navigating the node graph
+
+You can pan and zoom in or out the node graph.
+
+### Pan
+
+You can pan the view by clicking outside of any node or edge and dragging your mouse.
+
+### Zoom in or out
+
+Use the buttons on the upper left corner or use the mouse wheel, touch pad scroll, together with either Ctrl or Cmd key to zoom in or out.
+
+## Data API
+
+This visualization needs a specific shape of the data to be returned from the data source in order to correctly display it.
+
+Data source needs to return two data frames, one for nodes and one for edges and you also have to set `frame.meta.preferredVisualisationType = 'nodeGraph'` on both data frames.
+
+### Node parameters
+
+Required fields:
+
+| Field name | Type    | Description | 
+|------------|---------|-------------|
+| id         | string  | Unique identifier of the node. This ID is referenced by edge in it's source and target field. |
+
+Optional fields:
+
+| Field name | Type    | Description | 
+|------------|---------|-------------|
+| title      | string  | Name of the node visible in just under the node. |
+| subTitle   | string  | Additional, name, type or other identifier that will be shown right under the title. |
+| mainStat   | string/number  | First stat shown inside the node itself. Can be either string in which case the value will be shown as it is or it can be a number in which case any unit associated with that field will be also shown. |
+| secondaryStat   | string/number  | Same as mainStat but shown right under it inside the node. |
+| arc__*   | number  | Any field prefixed with `arc__` will be used to create the color circle around the node. All values in these fields should add up to 1. You can specify color using `config.color.fixedColor`. |
+| detail__*   | string/number  | Any field prefixed with `detail__` will be shown in the header of context menu when clicked on the node. Use `config.displayName` for more human readable label. |
+
+### Edge parameters
+
+Required fields:
+
+| Field name | Type    | Description | 
+|------------|---------|-------------|
+| id         | string  | Unique identifier of the edge. |
+| source     | string  | Id of the source node. |
+| target     | string  | Id of the target. |
+
+Optional fields:
+
+| Field name | Type    | Description | 
+|------------|---------|-------------|
+| mainStat   | string/number  | First stat shown in the overlay when hovering over the edge. Can be either string in which case the value will be shown as it is or it can be a number in which case any unit associated with that field will be also shown |
+| secondaryStat   | string/number  | Same as mainStat but shown right under it. |
+| detail__*   | string/number  | Any field prefixed with `detail__` will be shown in the header of context menu when clicked on the edge. Use `config.displayName` for more human readable label. |

docs/sources/whatsnew/whats-new-in-v7-4.md

@@ -36,6 +36,8 @@ All the information and stats shown in the Node graph beta are driven by the dat
 
 For more details about how to use the X-Ray service map feature, see the [X-Ray plugin documentation](https://grafana.com/grafana/plugins/grafana-x-ray-datasource).
 
+For more information, refer to [Node graph panel]({{< relref "../panels/visualizations/node-graph.md" >}}).
+
 ### New transformations
 
 The following transformations were added in Grafana 7.4.