Connect GraphQL APIs (Subgraphs)

This guide walks through a test use case for building, developing, and managing a GraphQL API with Apollo Server subgraphs.

Prerequisites

• Set up a GraphOS organization and member account

By the end of the milestone, you'll have:

• Installed the Rover CLI

• A federated graph with subgraphs running locally

• Sent an operation to your local GraphQL endpoint

Before you start

Rover is Apollo's official CLI for managing graphs and subgraphs. It's the main tool for setup, development, publishing schemas, and more.

Install and authenticate Rover by following the Rover CLI Getting Started guide.

Steps to complete

1. Set up your subgraph server locally

If you don't have an existing GraphQL API, choose your preferred programming language from the Rover templates to create a new server.

1rover template use my-new-subgraph

2. Store graph credentials

Copy the APOLLO_GRAPH_REF and APOLLO_KEY from your GraphOS account and paste into a .env file:

1# .env
2# (Formatted graph-id@variant, references a graph in the Apollo GraphOS platform)
3APOLLO_GRAPH_REF=
4
5# (This is your graph's API key)
6APOLLO_KEY=

You need these credentials to start the local dev server, even for local-only work.

3. Configure supergraph composition

Create a supergraph.yaml file in your project root to tell Rover how to compose your local graph:

1federation_version: =2.11.0
2subgraphs:
3  users:
4    routing_url: http://localhost:4001
5    schema:
6      file: ./users-schema.graphql
7  products:
8    routing_url: http://localhost:4002
9    schema:
10      file: ./products-schema.graphql

The routing_url must match the port where your subgraph server is running.

4. Start the local development server

Set your environment variables, then run:

1APOLLO_KEY=<YOUR_APOLLO_KEY> \
2APOLLO_GRAPH_REF=<YOUR_APOLLO_GRAPH_REF> \
3rover dev --supergraph-config supergraph.yaml

This command launches the router locally, composing your schema automatically. The Apollo Router serves your federated API at http://localhost:4000.

5. Test and iterate

Use Apollo Sandbox at http://localhost:4000 or any GraphQL client to send queries.

Modify schemas or resolvers as needed to refine your data model. The rover dev command automatically restarts and recomposes if your subgraph schema file changes.

Resources

• Apollo Federation Documentation