GraphQL Schema Stitching Demo

Schema stitching is the process of creating a single GraphQL schema from multiple underlying GraphQL APIs.

Schema stitching allows you to have one unified API that allows the client to query multiple GraphQL Schemas at the same time, including relations between the schemas.

Prerequisites

This demo requires Hasura's GraphQL Engine running with the following schema: A table called Person with columns id, name, and city.

Usage

npm install
HASURA_GRAPHQL_ENGINE_URL=http://localhost:9000 npm start

Change the HASURA_GRAPHQL_ENGINE_URL environment variable to point to a hasura graphql-engine with the person schema. Then, open localhost:8080/graphiql in your web browser, and start exploring with your query.

Merge Schemas

This demo combines two GraphQL schemas and exposes them on a single API:

1. The public GraphQL API of Meta Weather, to fetch the temperature information for a given city. Explore this on Apollo Launchpad
2. The Hasura GraphQL API, having a table called Person with columns id, name and city.

# Get weather info
query {
  cityWeather(city_name: "Bangalore") {
    city_name
    temp
    min_temp
    max_temp
    applicable_date
  }
}

# Get person data from Hasura Data API
query fetch_person {
  person {
    id
    name
    city
  }
}

We can extend the persons city column to include weather information.

extend type person {
  city_weather: CityWeather
}

Now this can be merged and queried using the same API like:

query {
    person {
       id
       name
       city
       # fetching weather after schema stitching
       city_weather {
        city_name
        temp
        min_temp
        max_temp
        applicable_date
      }
    }
}