Federation Supergraph

This example demonstrates how to consume the federation supergraph for a stitching gateway using @graphql-tools/federation package.

Schema Stitching is a framework or set of libraries that allows you to create gateways with a specific programmatic configuration. So it is flexible enough to consume any spec like Federation or Stitching SDL to create a gateway.

A federation supergraph SDL can be generated using Apollo Rover CLI. You can install Apollo Rover CLI here. In our example, we create a supergraph.yaml file for Supergraph configuration, and use rover supergraph compose --config ./supergraph.yaml > supergraph.graphql to generate an SDL for our gateway;

subgraphs:
  accounts:
    routing_url: http://localhost:4001/graphql
    schema:
      file: ./services/accounts.graphql
  inventory:
    routing_url: http://localhost:4002/graphql
    schema:
      file: ./services/inventory.graphql
  products:
    routing_url: http://localhost:4003/graphql
    schema:
      file: ./services/products.graphql
  reviews:
    routing_url: http://localhost:4004/graphql
    schema:
      file: ./services/reviews.graphql

Or you can get the supergraph sdl from a schema registry like GraphQL Hive

Sandbox

⬇️ Click ☰ to see the files

You can also see the project on GitHub here.

The following services are available for interactive queries:

• Stitched gateway: listening on 4000/graphql
• Accounts subservice_: listening on 4001/graphql
• Inventory subservice_: listening on 4002/GraphQL
• Products subservice_: listening on 4003/graphql
• Reviews subservice_: listening on 4004/graphql

This example is based on the Federation intro example.

Summary

You can use getStitchedSchemaFromSupergraphSdl from @graphql-tools/federation to consume a supergraph and get an executable GraphQLSchema that you can use with any GraphQL server or execute it locally.

import { readFileSync } from 'fs'
import { createServer } from 'node:http'
import { createYoga } from 'graphql-yoga'
import { getStitchedSchemaFromSupergraphSdl } from '@graphql-tools/federation'
 
// This doesn't have to be from a file system, it can be fetched via HTTP from a schema registry
const supergraphSdl = readFileSync('./supergraph.graphql').toString()
const schema = getStitchedSchemaFromSupergraphSdl({ supergraphSdl })
const yoga = createYoga({ schema })
const server = createServer(yoga)
 
server.listen(4000, () => {
  console.log(`🚀 Server ready at http://localhost:4000/graphql`)
})

Subscriptions are supported without the need of any additional configuration.

Authorization and Extra Headers

If you need to pass extra headers to the subgraphs, you can use httpExecutorOpts option to configure the HTTP executor;

const schema = getStitchedSchemaFromSupergraphSdl({
  supergraphSdl,
  httpExecutorOpts: {
    headers(executionRequest) {
      // This will forward `Authorization Header` from the incoming request to the subgraphs
      return {
        authorization: executionRequest.context.request.headers.get('authorization')
      }
    }
  }
})