Apollo Federation Subgraph support for HotChocolate.
$ dotnet add package ApolloGraphQL.HotChocolate.Federation
This is a fork of
HotChocolate.Federationmodule that aims to provide first class Apollo Federation support for subgraphs.
HotChocolateApollo Federation is a powerful, open architecture that helps you create a unified supergraph that combines multiple GraphQL APIs.
ApolloGraphQL.HotChocolate.Federation provides Apollo Federation support for building subgraphs in the HotChocolate ecosystem. Individual subgraphs can be run independently of each other but can also specify
relationships to the other subgraphs by using Federated directives. See Apollo Federation documentation for details.
ApolloGraphQL.HotChocolate.Federation package is published to Nuget. Update your .csproj file with following package references
<ItemGroup>
<!-- make sure to also include HotChocolate package -->
<PackageReference Include="HotChocolate.AspNetCore" Version="13.5.1" />
<!-- federation package -->
<PackageReference Include="ApolloGraphQL.HotChocolate.Federation" Version="$LatestVersion" />
</ItemGroup>After installing the necessary packages, you need to register Apollo Federation with your GraphQL service.
var builder = WebApplication.CreateBuilder(args);
builder.Services
.AddGraphQLServer()
.AddApolloFederation()
// register your types and services
;
var app = builder.Build();
app.MapGraphQL();
app.Run();Refer to HotChocolate documentation for detailed information on how to create GraphQL schemas and configure your server.
Apollo Federation requires subgraphs to provide some additional metadata to make them supergraph aware. Entities are GraphQL objects that can be uniquely identified across
the supergraph by the specified @keys. Since entities can be extended by various subgraphs, we need an extra entry point to access the entities, i.e. subgraphs need to
implement reference resolvers for entities that they support.
Currently ApolloGraphQL.HotChocolate.Federation supports only Apollo Federation v1. See Apollo documentation for additional Federation details.
All federated directives are provided as attributes that can be applied directly on classes/fields/methods.
[Key("id")]
public class Product
{
public Product(string id, string name, string? description)
{
Id = id;
Name = name;
Description = description;
}
[ID]
public string Id { get; }
public string Name { get; }
public string? Description { get; }
// assumes ProductRepository with GetById method exists
// reference resolver method must be public static
[ReferenceResolver]
public static Product GetByIdAsync(
string id,
ProductRepository productRepository)
=> productRepository.GetById(id);
}This will generate following type
type Product @key(fields: "id") {
id: ID!
name: String!
description: String
}Directives
Key applicable on objects, see @key documentationExtends applicable on objects, see @extends documentationExternal applicable on fields, see @external documentationProvides applicable on fields, see @provides documentationRequires applicable on fields, see @requires documentationEntity resolution
Map applicable on entity resolver method paramaters, allows you to map complex argument to a simpler representation value, e.g. [Map("foo.bar")] string barReferenceResolver applicable on static public methods to indicate entity resolverAlternatively, if you need more granular control, you can use code first approach and manually populate federation information on the underlying GraphQL type descriptor. All federated directives expose corresponding methods on the applicable descriptor.
public class Product
{
public Product(string id, string name, string? description)
{
Id = id;
Name = name;
Description = description;
}
[ID]
public string Id { get; }
public string Name { get; }
public string? Description { get; }
}
public class ProductType : ObjectType<Product>
{
protected override void Configure(IObjectTypeDescriptor<Product> descriptor)
{
descriptor
.Key("id")
.ResolveReferenceWith(t => GetProduct(default!, default!));
}
private static Product GetProduct(
string id,
ProductRepository productRepository)
=> productRepository.GetById(upc);
}This will generate following type
type Product @key(fields: "id") {
id: ID!
name: String!
description: String
}If you have a specific question about the library or code, please start a discussion in the Apollo community forums or start a conversation on our Discord server.
To get started, please fork the repo and checkout a new branch. You can then build the library locally by running
# install dependencies
dotnet restore
# build project
dotnet build
# run tests
dotnet testSee more info in CONTRIBUTING.md.
After you have your local branch set up, take a look at our open issues to see where you can contribute.
For more info on how to contact the team for security issues, see our Security Policy.
This library is licensed under The MIT License (MIT).