Can subgraphs access data from other subgraphs?

Schema Design
1

Hey all :wave:

At the moment I’m creating a greenfield project and we chose to go with micro-services on GraphQL.

The stack
A little context, we’re using Prisma as the ORM and Nexus JS for the declarative, code-first GraphQL schemas for TypeScript support.

Business context
I’ve managed to have a working (non-managed for the time being) @apollo/gateway with some federated sub-graphs (using prisma and nexus).

At the moment I’ve created two services:

  • identity-service - handles the user logic, authentication, sign-up’s, jwt tokens emission
  • cart-service - holds the user’s cart data.

State of the art
When I create a user, then, create a cart with the previously created user (providing the userId), on the gateway level I can see the the user.cart.{id, userId}.

The issue
On the identity-service, I have a signup Mutation which creates a User with all user specific data : name, email, password, .... Since identity-service has no visibility on what cart-service implementation is, I can’t attach a cart on the identity-service directly.

The user data model can live without a cartId associated and thats perfectly fine. The issue is, when, on the frontend, I submit a mutation, I would like the frontend to don’t care about this implementation details.

To signup a user I must run the following mutation

mutation SignupMutation($signupEmail: String!, $signupFirstName: String!, $signupLastName: String!, $signupPassword: String!) {
  signup(email: $signupEmail, firstName: $signupFirstName, lastName: $signupLastName, password: $signupPassword) {
    token
  }
}

mutation SignupMutation($createOneCartData: CartCreateInput!) {
  createOneCart(data: $createOneCartData) {
    id
  }
}

mutation AttachCartToUserMutation($attachCartToUserCartId: String!, $attachCartToUserUserId: String!) {
  attachCartToUser(cartId: $attachCartToUserCartId, userId: $attachCartToUserUserId) {
    id
  }
}

Useful links

If you’d like for me to share my repos with my implementations, I’d be glad to do so.

Thank you so much in advance.

2

Different subgraphs can reference things in other subgraphs via the extend type <name> @key(fields: "...") and @external directives.

This allows you to define a foreign key relationship between your entities in your API.

If you’re referring to federating a gateway into another gateway, I don’t believe that use case is supported right now.

3

@kevin-lindsay-1 If we want to pass same set of input arguments to nested resolvers across subgraph is @key the only way. Basically we want to pass a set of input arguments to referred services.

1 Like
4

Can you give an example?

5

i am also curious to know if this is possible… what is the best approach in passing multiple arguments across nested resolvers?