Buffalo, gqlgen, and graphql subscriptions

Mar 21, 2020 - 2 minutes

Here’s a sample application to show how to stitch together Buffalo, gqlgen and graphql subscriptions. Github Repo

I’ll go over the important parts here. After generating your buffalo application you’ll need a graphql schema file and a gqlgen config file:

1# schema.graphql
2type Example {
3	message: String
4}
5
6
7type Subscription {
8    exampleAdded: Example!
9}

and your config file:

 1# gqlgen.yml
 2struct_tag: json
 3schema:
 4- schema.graphql
 5exec:
 6  filename: exampleql/exec.go
 7  package: exampleql
 8model:
 9  filename: exampleql/models.go
10  package: exampleql
11resolver:
12  filename: exampleql/resolver.go
13  type: Resolver

Next lets generate our graphql files:

1go run github.com/99designs/gqlgen --verbose

Now we can open up our resolver.go file and add a New method to make creating the handler easier:

1func New() Config {
2	return Config{
3		Resolvers: &Resolver{},
4	}
5}

Let’s also add our resolver implementation:

 1func (r *subscriptionResolver) ExampleAdded(ctx context.Context) (<-chan *Example, error) {
 2	msgs := make(chan *Example, 1)
 3
 4	go func() {
 5		for {
 6			msgs <- &Example{Message: randString(50)}
 7			time.Sleep(1 * time.Second)
 8		}
 9	}()
10	return msgs, nil
11}
12
13var letterRunes = []rune("abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ")
14
15func randString(n int) *string {
16	b := make([]rune, n)
17	for i := range b {
18		b[i] = letterRunes[rand.Intn(len(letterRunes))]
19	}
20	s := string(b)
21	return &s
22}

Inside your app.go file you’ll need to add a few handlers and wrap them in buffalo’s handler as well:

 1c := cors.New(cors.Options{
 2	AllowedOrigins:   []string{"http://localhost:3000"},
 3	AllowCredentials: true,
 4})
 5
 6srv := handler.New(exampleql.NewExecutableSchema(exampleql.New()))
 7srv.AddTransport(transport.POST{})
 8srv.AddTransport(transport.Websocket{
 9	KeepAlivePingInterval: 10 * time.Second,
10	Upgrader: websocket.Upgrader{
11		CheckOrigin: func(r *http.Request) bool {
12			return true
13		},
14	},
15})
16
17app.ANY("/query", buffalo.WrapHandler(c.Handler(srv)))
18
19app.GET("/play", buffalo.WrapHandler(playground.Handler("Example", "/query")))

Now if you head over to the playground and run this query:

1subscription {
2  exampleAdded {
3    message
4  }
5}

You should see something like this scrolling by:

Things to note:

This is not production ready code
If you were doing something with multiple load balanced nodes you should be using something like Redis or NATs pubsub to handle messaging
This isn’t cleaning up channels or doing anything that you should be doing for live code

{ Josh Rendek }

Buffalo, gqlgen, and graphql subscriptions

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