GraphQL Remote Loader

Performant, batched GraphQL queries from within the resolvers of a graphql-ruby API.

Snippet

field :login, String, null: false, description: "The currently authenticated GitHub user's login."

def login
  GitHubLoader.load("viewer { login }").then do |results|
    if results["errors"].present?
      ""
    else
      results["data"]["viewer"]["login"].upcase
    end
  end
end

Description

graphql-remote_loader allows for querying GraphQL APIs from within resolvers of a graphql-ruby API.

This can be used to create GraphQL APIs that depend on data from other GraphQL APIs, either remote or local.

A promise-based resolution strategy from Shopify's graphql-batch is used to batch all requested data into a single GraphQL query. Promises are fulfilled with only the data they requested.

You can think of it as a lightweight version of schema-stitching.

Performance

Each Loader#load invocation does not send a GraphQL query to the remote. The Gem uses graphql-batch to collect all GraphQL queries together, then combines them and sends a single query to the upstream. The gem splits the response JSON up so that each promise is only resolved with data that it asked for.

How to use

First, you'll need to install the gem. Either do gem install graphql-remote_loader or add this to your Gemfile:

gem "graphql-remote_loader"

The gem provides a base loader GraphQL::RemoteLoader::Loader which does most of the heavy lifting. In order to remain client-agnostic, there's an unimplemented no-op that takes a query string and queries the remote GraphQL API.

To use, create a new class that inherits from GraphQL::RemoteLoader::Loader and define def query(query_string). The method takes a query String as input. The expected output is a response Hash, or an object that responds to #to_h.

Example:

require "graphql/remote_loader"

module MyApp
  class GitHubLoader < GraphQL::RemoteLoader::Loader
    def query(query_string)
      parsed_query = GraphQLClient.parse(query_string)
      GraphQLClient.query(parsed_query)
    end
  end
end

This example uses graphql-client. Any client, or even just plain cURL/HTTP can be used.

With your loader setup, you can begin using #load or #load_value in your graphql-ruby resolvers.

Full example

To see a working example of how graphql-remote_loader works, see the complete, working example application.

Running tests

bundle install
bundle exec rspec