Go GraphQL in LINE SPOT Golang Taipei Gathering #40 

Hello, I'm Denny. I work at LINE . 

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2019 Q3 

API Gateway with Go & GraphQL for Microservices 

API Gateway Go GraphQL 

Client to Monolith 

Client to Microservices HTTP HTTP HTTP HTTP HTTP HTTP 

Client to Microservices HTTP HTTP HTTP gRPC Thrift xRPC 

Client to API Gateway to Microservices backend for frontend 

Client to API Gateway 

REST API 

https://api.github.com/search/repositories?q=language:go&sort=stars&order=desc { "items": [ { "id": 23096959, "node_id": "MDEwOlJlcG9zaXRvcnkyMzA5Njk1OQ==", "name": "go", "full_name": "golang/go", "owner": { "login": "golang" }, "url": "https://api.github.com/repos/golang/go", "description": "The Go programming language", "issues_url": "https://api.github.com/repos/golang/go/issues{/number}", "stargazers_count": 56341 } ] } 

https://api.github.com/repos/golang/go/issues [ { "url": "https://api.github.com/repos/golang/go/issues/31459", "number": 31459, "title": "cmd/link: Apple's symbols tool unable to read DWARF data from c-archive go.o", "user": { "login": "tmm1", "avatar_url": "https://avatars2.githubusercontent.com/u/2567?v=4", }, "state": "open" }, { "url": "https://api.github.com/repos/golang/go/issues/31458", "number": 31458, "title": "cmd/go: mod meta tag causes infinite loop in GOPROXY", "user": { "login": "marwan-at-work", "avatar_url": "https://avatars0.githubusercontent.com/u/16294261?v=4", }, "state": "open" } ] 

Client to API Gateway 

Multiple Client Types to API Gateway 

Consumer centric API 

GraphQL 

Query language 

Single endpoint 

Response shape defined by the client 

Transport agnostic 

{ repository( owner: "golang" name: "go" ) { name issues( first: 2 orderBy: { field: CREATED_AT direction: DESC } ) { totalCount nodes { number title } } } } { "data": { "repository": { "name": "go", "issues": { "totalCount": 30761, "nodes": [ { "number": 31459, "title": "cmd/link: Apple's symbols tool ..." }, { "number": 31458, "title": "cmd/go: mod meta tag causes ..." } ] } } } } 

{ repository( owner: "golang" name: "go" ) { name issues( first: 2 orderBy: { field: CREATED_AT direction: DESC } ) { totalCount nodes { number title } } } } { "data": { "repository": { "name": "go", "issues": { "totalCount": 30761, "nodes": [ { "number": 31459, "title": "cmd/link: Apple's symbols tool ..." }, { "number": 31458, "title": "cmd/go: mod meta tag causes ..." } ] } } } } 

Queries and Mutations 

GraphQL schema is typed 

query { repository( owner: String! name: String! ): Repository } type Repository { name: String! issues( orderBy: IssueOrder first: Int ): IssueConnection! } type IssueConnection { totalCount: Int! nodes: [Issue] } type Issue { number: Int! title: String! } { repository( owner: "golang" name: "go" ) { name issues( first: 2 orderBy: { field: CREATED_AT direction: DESC } ) { totalCount nodes { number title } } } } type IssueOrder { field: IssueOrderField! direction: OrderDirection! } enum IssueOrderField { CREATED_AT UPDATED_AT COMMENTS } enum OrderDirection { ASC DESC } 

mutation { createIssue( input: CreateIssueInput! ): CreateIssuePayload } type CreateIssuePayload { clientMutationId: String issue: Issue } input CreateIssueInput { repositoryId: ID! title: String! body: String assigneeIds: [ID!] milestoneId: ID labelIds: [ID!] projectIds: [ID!] clientMutationId: String } mutation { createIssue( input: { repositoryId: "..." title: "New issue" body: "This is a new issue" } ) { clientMutationId issue { number title } } } 

graphql.org 

Tooling 

GraphiQL 

GraphQL Playground 

Create a GraphQL server with Go 

graphql-go/graphql graph-gophers/graphql-go 99designs/gqlgen 

gqlgen 

Schema first 

Type safe 

Less boilerplate 

Create a schema type Query { posts: [Post] post(id: Int!): Post } type Post { id: Int! title: String! body: String! } 

Initialize with gqlgen ➜ apigateway go run github.com/99designs/gqlgen init Exec "go run ./server/server.go" to start GraphQL server ➜ apigateway tree . ├── generated.go ├── go.mod ├── go.sum ├── gqlgen.yml ├── models_gen.go ├── resolver.go ├── schema.graphql └── server └── server.go 

Resolver Interface type QueryResolver interface { Posts(ctx context.Context) ([]*Post, error) Post(ctx context.Context, id int) (*Post, error) } 

Resolvers type Resolver struct{} func (r *Resolver) Query() QueryResolver { return &queryResolver{r} } type queryResolver struct{ *Resolver } func (r *queryResolver) Posts(ctx context.Context) ([]*Post, error) { panic("not implemented") } func (r *queryResolver) Post(ctx context.Context, id int) (*Post, error) { panic("not implemented") } 

Generated models type Post struct { ID int `json:"id"` Title string `json:"title"` Body string `json:"body"` } 

Configuration schema: - schema.graphql exec: filename: generated.go model: filename: models_gen.go resolver: filename: resolver.go type: Resolver models: Post: model: apigateway.Post 

Generated server const defaultPort = "8080" func main() { port := os.Getenv("PORT") if port == "" { port = defaultPort } http.Handle("/", handler.Playground("GraphQL playground", "/query")) http.Handle("/query", handler.GraphQL(apigateway.NewExecutableSchema(...))) log.Printf("connect to http://localhost:%s/ for GraphQL playground", port) log.Fatal(http.ListenAndServe(":"+port, nil)) } 

Create a GraphQL schema Initialize with gqlgen Implement resolvers Update GraphQL schema Generate new code with gqlgen Implement new resolvers 

Demo 

Authentication Quotas/Rate limiting Request logging ... 

Hello, I'm YourName. I work at LINE . 

Thanks!