Programming language: Go
License: MIT License
Tags: Query Language    

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api-fu (noun)

  1. (informal) Mastery of APIs. ๐Ÿ’ช


  • The top level apifu package is an opinionated library that aims to make it as easy as possible to build APIs that conform to API-fu's ideals. See the examples directory for example usage.
  • The graphql package is an unopinionated library for building GraphQL APIs. If you agree with API-fu's ideals, you should use apifu instead, but if you want something lower level, the graphql package is still an excellent standalone GraphQL library. It fully supports all features of the June 2018 spec.
  • The graphqlws package is an unopinionated library for using the Apollo graphql-ws protocol. This allows you to serve your GraphQL API via WebSockets and provide subscription functionality.


API-fu builds GraphQL APIs with code. To begin, you need a config that at least defines a query field:

var fuCfg apifu.Config

fuCfg.AddQueryField("foo", &graphql.FieldDefinition{
    Type: graphql.StringType,
    Resolve: func(ctx *graphql.FieldContext) (interface{}, error) {
        return "bar", nil

From there, you can build the API:

fu, err := apifu.NewAPI(&fuCfg)
if err != nil {

And serve it:

fu.ServeGraphQL(w, r)

API-fu also has first-class support for common patterns such as nodes that are queryable using global ids. See the examples directory for more complete example code.


โœ… Supports all features of the latest GraphQL spec.

This includes null literals, error extensions, subscriptions, and directives.

๐Ÿš… Fast!

The graphql package is over twice as fast and several times more memory efficient than its inspiration (graphql-go/graphql).

pkg: github.com/ccbrown/api-fu/graphql/benchmarks
BenchmarkAPIFu-16                765       1553517 ns/op      890575 B/op      22587 allocs/op
BenchmarkGraphQLGo-16            315       3753681 ns/op     3990220 B/op      45952 allocs/op

โšก๏ธ Supports efficient batching and concurrency without the use of goroutines.

The graphql package supports virtually any batching or concurrency pattern using low level primitives.

The apifu package provides high level ways to use them.

For example, you can define a resolver like this to do work in a goroutine:

fuCfg.AddQueryField("myField", &graphql.FieldDefinition{
    Type: graphql.IntType,
    Resolve: func(ctx *graphql.FieldContext) (interface{}, error) {
        return Go(ctx.Context, func() (interface{}, error) {
            return doSomethingComplex(), nil
        }), nil

Or you can define a resolver like this to batch up queries, allowing you to minimize round trips to your database:

fuCfg.AddQueryField("myField", &graphql.FieldDefinition{
    Type: graphql.IntType,
    Resolve: Batch(func(ctx []*graphql.FieldContext) []graphql.ResolveResult {
        return resolveABunchOfTheseAtOnce(ctx)

๐Ÿ’ก Provides implementations for commonly used scalar types.

For example, the apifu package provides date-time and long (but JavaScript safe) integers.

๐Ÿ“ก Implements handlers for HTTP and the Apollo graphql-ws protocol.

Once you've built your API, all you have to do is:

fu.ServeGraphQL(w, r)


fu.ServeGraphQLWS(w, r)

๐Ÿ“– Provides easy-to-use helpers for creating connections adhering to the Relay Cursor Connections Specification.

Just provide a name, cursor constructor, edge fields, and edge getter:

    "messagesConnection": apifu.TimeBasedConnection(&apifu.TimeBasedConnectionConfig{
        NamePrefix: "ChannelMessages",
        EdgeCursor: func(edge interface{}) apifu.TimeBasedCursor {
            message := edge.(*model.Message)
            return apifu.NewTimeBasedCursor(message.Time, string(message.Id))
        EdgeFields: map[string]*graphql.FieldDefinition{
            "node": &graphql.FieldDefinition{
                Type: graphql.NewNonNullType(messageType),
                Resolve: func(ctx *graphql.FieldContext) (interface{}, error) {
                    return ctx.Object, nil
        EdgeGetter: func(ctx *graphql.FieldContext, minTime time.Time, maxTime time.Time, limit int) (interface{}, error) {
            return ctxSession(ctx.Context).GetMessagesByChannelIdAndTimeRange(ctx.Object.(*model.Channel).Id, minTime, maxTime, limit)

๐Ÿ›  Can generate Apollo-like client-side type definitions and validate queries in source code.

The gql-client-gen tool can be used to generate types for use in client-side code as well as validate queries at compile-time. The generated types intelligently unmarshal inline fragments and fragment spreads based on __typename values.

See [cmd/gql-client-gen](cmd/gql-client-gen) for details.

๐Ÿš” Calculates operation costs during validation for rate limiting and metering

During validation, you can specify a max operation cost or get the actual cost of an operation using customizable cost definitions:

doc, errs := graphql.ParseAndValidate(req.Query, req.Schema, req.ValidateCost(maxCost, &actualCost))

API Design Guidelines

The following are guidelines that are recommended for all new GraphQL APIs. API-fu aims to make it easy to conform to these for robust and future-proof APIs:

  • All mutations should resolve to result types. No mutations should simply resolve to a node. For example, a createUser mutation should resolve to a CreateUserResult object with a user field rather than simply resolving to a User. This is necessary to keep mutations extensible. Likewise, subscriptions should not resolve directly to node types. For example, a subscription for messages in a chat room (chatRoomMessages) should resolve to a ChatRoomMessagesEvent type.
  • Nodes with 1-to-many relationships should make related nodes available via Relay Cursor Connections. Nodes should not have fields that simply resolve to lists of related nodes. Additionally, all connections must require a first or last argument that specifies the upper bound on the number of nodes returned by that connection. This makes it possible to determine an upper bound on the number of nodes returned by a query before that query begins execution, e.g. using rules similar to GitHub's.
  • Mutations that modify nodes should always include the updated version of that node in the result. This makes it easy for clients to maintain up-to-date state and tolerate eventual consistency (If a client updates a resource, then immediately requests it in a subsequent query, the server may provide a version of the resource that was cached before the update.).
  • Nodes should provide revision numbers. Each time a node is modified, the revision number must increment. This helps clients maintain up-to-date state and enables simultaneous change detection.
  • It should be easy for clients to query historical data and subscribe to real-time data without missing anything due to race conditions. The most transparent and fool-proof way to facilitate this is to make subscriptions immediately push a small history of events to clients as soon as they're started. The pushed history should generally only need to cover a few seconds' worth of events. If queries use eventual consistency, the pushed history should be at least as large as the query cache's TTL.

Versioning and Compatibility Guarantees

This library is not versioned. However, one guarantee is made: Any backwards-incompatible changes made will break your build at compile-time. If your application compiles after updating API-fu, you're good to go.