Federation question

[timpie90]

I'm quite new to GraphQl and have a question about something.

Every example I see has the same structure, a Entity e.g. Show and another Entity Review where a show has multiple reviews.

I implemented this as a Customer and Order entity where a customer can have multiple orders. I created two separate services: CustomerService and OrderService both created with DGS framework. And a apollo-server with apollo-gateway which consumes the graphql endpoints.

Following schemas:

# Customer schema
type Query {
    customers: [Customer]
    customer(id: String): Customer
}

type Customer @key(fields: "id"){
    id: ID
    name: Name
    address: Address
    contactInformation: ContactInformation
}

type Name {
    firstName: String
    lastName: String
}

type Address {
    streetName: String
    houseNumber: String
    city: String
    zipCode: String
}

type ContactInformation {
    email: String
    phoneNumber: String
}

# Order Schema
type Query {
    orders: [Order]
    order(id: ID!): Order
}

type Customer @key(fields: "id") @extends {
    id: ID @external
    orders: [Order]
}

type Order {
    id: ID
    customerId: ID
    delivered: Boolean
    paid: Boolean
    items: [Item]
}

type Item {
    id: ID!
    quantity: Int!
}

This works fine and I can query customers with their orders.

What I want is to be able to also query orders with the customer information. But I have a hard time to find any documentation about how to do that. Can someone point me in the right direction? What I think I need to do is add a customer: Customer to the Order type, but I don't know how to write the data fetcher for that. Or is this totally against the idea of GraphQl and should I not implement it this way, if so what is the best way?

[congotej]

@timpie90 Welcome to the GraphQL world! We are happy to help with any DGS specific questions, but from what I can understand your question is more centered around Apollo Federation. They have some great docs around this: https://www.apollographql.com/docs/federation/federated-types/overview, as well as repos: https://github.com/apollographql/federation-jvm and https://github.com/apollographql/apollo-federation-subgraph-compatibility.

What I can say upon looking at your schema is that you can leverage Apollo directives like @provides and @requires (https://www.apollographql.com/docs/federation/federated-types/federated-directives#provides) to tell the gateway where to fetch data from. But again, please refer to Apollo docs since that is entirely separate from the DGS framework.

As far as data fetchers are concerned, make sure that they are set up accordingly to fetch the necessary data from the underlying data sources (e.g., databases) based on the customerId field in the Order service and the id field in the Customer service, for example. You can find more info on datafetching here.

I am going to close this issue for now, but please feel free to open a new one if you have any DGS framework questions.