> ## Documentation Index
> Fetch the complete documentation index at: https://wundergraphinc-brendan-add-external-directive.mintlify.site/llms.txt
> Use this file to discover all available pages before exploring further.

# NATS

> NATS event provider support for EDFS

<Frame caption="NATS with EDFS">
  <img src="https://mintlify.s3.us-west-1.amazonaws.com/wundergraphinc-brendan-add-external-directive/images/router/event-driven-federated-subscriptions-edfs/image-1.png" />
</Frame>

## Minimum requirements

| Package      | Minimum version |
| ------------ | --------------- |
| controlplane | 0.88.3          |
| router       | 0.88.0          |
| wgc          | 0.55.0          |

## Full schema example

Here is a comprehensive example of how to use NATS with EDFS. This guide covers request, publish, subscribe directive. All examples can be modified to suit your specific needs. The schema directives and `edfs__*` types belong to the EDFS schema contract and must not be modified.

```js
# EDFS

directive @edfs__natsRequest(subject: String!, providerId: String! = "default") on FIELD_DEFINITION
directive @edfs__natsPublish(subject: String!, providerId: String! = "default") on FIELD_DEFINITION
directive @edfs__natsSubscribe(subjects: [String!]!, providerId: String! = "default", streamConfiguration: edfs__NatsStreamConfiguration) on FIELD_DEFINITION

type edfs__PublishResult {
    success: Boolean!
}

input edfs__NatsStreamConfiguration {
    consumerInactiveThreshold: Int! = 30
    consumerName: String!
    streamName: String!
}

# Custom

type Query {
    employeeFromEvent(id: Int!): Employee! @edfs__natsRequest(subject: "getEmployee.{{ args.id }}", providerId: "my-nats")
    employeeFromEventMyNats(employeeID: Int!): Employee! @edfs__natsRequest(subject: "getEmployeeMyNats.{{ args.employeeID }}", providerId: "my-nats")
}

input UpdateEmployeeInput {
    name: String
    email: String
}

type Mutation {
    updateEmployeeMyNats(employeeID: Int!, update: UpdateEmployeeInput!): edfs__PublishResult! @edfs__natsPublish(subject: "employeeUpdatedMyNats.{{ args.employeeID }}", providerId: "my-nats")
}

type Subscription {
    employeeUpdated(employeeID: Int!): Employee! @edfs__natsSubscribe(subjects: ["employeeUpdated.{{ args.employeeID }}"])
    employeeUpdatedMyNats(id: Int!): Employee! @edfs__natsSubscribe(subjects: ["employeeUpdatedMyNats.{{ args.id }}", "employeeUpdatedMyNatsTwo.{{ args.id }}"], providerId: "my-nats")
    employeeUpdatedNatsStream(id: Int!): Employee! @edfs__natsSubscribe(subjects: ["employeeUpdated.{{ args.id }}"], streamConfiguration: { consumerName: "consumerName", streamName: "streamName"}, providerId: "my-nats")
}

# Subgraph schema

type Employee @key(fields: "id", resolvable: false) {
  id: Int! @external
}
```

You can create the Event-Driven Graph (EDG—an abstract subgraph) with the following [wgc](/cli/intro) command:

```js
wgc subgraph publish edg --namespace default --schema edg.graphqls
```

## Router configuration

Based on the example above, you will need a compatible router configuration.

<CodeGroup>
  ```yaml config.yaml
  events:
    providers:
      nats:
        - id: my-nats
          url: "nats://localhost:4222"
          authentication:
            token: "token" # or
            user_info:
              username: "username"
              password: "password"
  ```
</CodeGroup>

## Example Query

In the example query below, one or more subgraphs have been implemented alongside the Event-Driven Graph to resolve any other fields defined on `Employee`, e.g., `tag` and `details.surname`.

Event-Driven Graphs (EDGs) do not define resolvers, and can only define fields that compose an entity's primary key(s).

```js
subscription {
  employeeUpdated(employeeID: 1) {
    id # resolved by the Event-Driven Graph (through the event)
    tag # resolved by another subgraph
    details { # resolved by another subgraph
      surname
    }
  }
}
```

## System diagram

<Frame>
  <img src="https://mintlify.s3.us-west-1.amazonaws.com/wundergraphinc-brendan-add-external-directive/images/router/event-driven-federated-subscriptions-edfs/image-2.png" />
</Frame>