## Description

Create a feature subgraph based on an existing subgraph for your federated graph within the specified (otherwise “default”) namespace. A feature subgraph is an “override” of an existing subgraph. One or more feature subgraphs are used to compose a [feature flag](https://cosmo-docs.wundergraph.com/cli/feature-flags).

## Minimum Requirements

| Package | Minimum version |
| --- | --- |
| [wgc](https://cosmo-docs.wundergraph.com/cli/intro) | [0.58.0](https://github.com/wundergraph/cosmo/compare/wgc@0.57.7...wgc@0.58.0) |
| [router](https://cosmo-docs.wundergraph.com/router/intro) | [0.95.0](https://github.com/wundergraph/cosmo/releases/tag/router%400.95.0) |

## Usage

A feature subgraph does not function in isolation. One or more feature subgraphs must compose a [feature flag](https://cosmo-docs.wundergraph.com/cli/feature-flags), which itself must be enabled to take effect.

```
wgc feature-subgraph create my-feature-subgraph --subgraph my-subgraph --routing-url http://localhost:4000
```

The alias for `feature-subgraph` is `fs`. Note that unless specified by the `--namespace` parameter, the namespace will be automatically passed as “default”.

The type of the feature subgraph is determined by the type of the base subgraph. For example, if the base subgraph is a plugin subgraph, the feature subgraph will also be a plugin subgraph.

## Parameters

- `<name>`: The name of the feature subgraph to create. Must be unique among all subgraphs and feature subgraphs within the specified (otherwise “default”) namespace.

## Required Options

If the base subgraph does not exist in the specified (otherwise “default”) namespace, the command will fail.

`--subgraph`: The name of the existing base subgraph for which the feature subgraph is to be created.

## Options

Feature subgraphs do not use labels directly; labels are set by the [feature flag](https://cosmo-docs.wundergraph.com/cli/feature-flags) that the feature subgraph(s) compose.

If the base subgraph is not a plugin subgraph, the routing url is required.

- `-r , --routing-url`: Set the URL for the subgraph’s data source. This URL defines the endpoint from which the subgraph will fetch data.
- `-n, --namespace` : The namespace of the feature subgraph (defaults to “default”). Returns an error if the feature flag does not exist in that namespace.
- `--subscription-url:` Use a different URL for subscription requests. If no subscription URL is provided, the router URL is used for subscriptions.
- `--subscription-protocol:` Set a protocol to use for subscriptions. The available options are:  - `ws` (default): Negotiate an appropriate protocol over websockets. Both `graphql-ws` and `subscription-transport-ws` are supported.
  - `sse`: Use Server-Sent Events with a GET request.
  - `sse_post`: Use Server-Sent events with a POST request.

## Examples

- Create the feature subgraph “my-feature-subgraph” based on the existing subgraph “my-subgraph” in the namespace “prod”.

```
wgc feature-subgraph create my-feature-subgraph \
	--subgraph my-subgraph \
	--namespace prod \
	--routing-url http://localhost:4000
```