federation

README

Federation plugin

Add support for graphql federation in your graphql Go server!

TODO(miguel): add details.

Tests

There are several different tests. Some will process the configuration file directly. You can see those in the federation_test.go. There are also tests for entity resolvers, which will simulate requests from a federation server like Apollo Federation.

Running entity resolver tests.

1. Go to plugin/federation
2. Run the command go generate
3. Run the tests with go test ./....

Architecture

TODO(miguel): add details.

Entity resolvers - GetMany entities

The federation plugin implements GetMany semantics in which entity resolvers get the entire list of representations that need to be resolved. This functionality is currently optin tho, and to enable it you need to specify the directive @entityResolver in the federated entity you want this feature for. E.g.

directive @entityResolver(multi: Boolean) on OBJECT

type MultiHello @key(fields: "name") @entityResolver(multi: true) {
    name: String!
}

That allows the federation plugin to generate GetMany resolver function that can take a list of representations to be resolved.

From that entity type, the resolver function would be

func (r *entityResolver) FindManyMultiHellosByName(ctx context.Context, reps []*generated.ManyMultiHellosByNameInput) ([]*generated.MultiHello, error) {
  /// <Your code to resolve the list of items>
}

Note: If you are using omit_slice_element_pointers: true option in your config yaml, your GetMany resolver will still generate in the example above the same signature FindManyMultiHellosByName(ctx context.Context, reps []*generated.ManyMultiHellosByNameInput) ([]*generated.MultiHello, error). But all other instances will continue to honor omit_slice_element_pointers: true

Documentation

Index

• func New(version int) plugin.Plugin
• type Entity
• type EntityResolver
  • func (e *EntityResolver) LookupInputType() string
• type KeyField
• type Requires

Functions

func New

func New(version int) plugin.Plugin

New returns a federation plugin that injects federated directives and types into the schema

Types

type Entity

type Entity struct {
	Name      string // The same name as the type declaration
	Def       *ast.Definition
	Resolvers []*EntityResolver
	Requires  []*Requires
	Multi     bool
}

Entity represents a federated type that was declared in the GQL schema.

type EntityResolver

type EntityResolver struct {
	ResolverName  string      // The resolver name, such as FindUserByID
	KeyFields     []*KeyField // The fields declared in @key.
	InputType     types.Type  // The Go generated input type for multi entity resolvers
	InputTypeName string
}

func (*EntityResolver) LookupInputType

func (e *EntityResolver) LookupInputType() string

type KeyField

type KeyField struct {
	Definition *ast.FieldDefinition
	Field      fieldset.Field        // len > 1 for nested fields
	Type       *config.TypeReference // The Go representation of that field type
}

type Requires

type Requires struct {
	Name  string                // the name of the field
	Field fieldset.Field        // source Field, len > 1 for nested fields
	Type  *config.TypeReference // The Go representation of that field type
}

Requires represents an @requires clause