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Federation Supergraph

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 = await 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.