Graph ql api gateway
- 1. GraphQL API Gateway Go code generation isn’t frightful. Yaroslav Mytso Software engineer at EGT Ukraine
- 2. Service 1 (GRPC API) Service 2 (GRPC API) Service 3 (GRPC API) Service N (GRPC API) Front-end X X X X
- 3. API Gateway Service 1 (GRPC API) Service 2 (GRPC API) Service 3 (GRPC API) Service N (GRPC API) Front-end
- 4. { user(id: «1») { name } dog(name: «A»){ nick } } { «user»: { «name»: «UserName» }, «dog»: { «nick»: «Bobby» } } Type: User Type: Pet Type: String Type: String Type: Query
- 5. GraphQL → GRPC Proxy writing process GRPC Message GraphQL Output Object GraphQL Input Object GRPC Service GraphQL Fields Array GRPC Enum GraphQL Enum Input Object unmarshaler+ GRPC Method Method Resolver
- 6. Message in .proto file VS Message in GraphQL Schema message A { int32 someField = 1; int64 someAnotherField = 2; string andAnotherOne = 3; } var GQLA = graphql.NewObject(graphql.ObjectConfig{ Name: "A", Fields: graphql.Fields{ "someField": &graphql.Field{ Name: "someField", Type: graphql.Int, Resolve: func(p graphql.ResolveParams) (interface{}, error) { switch src := p.Source.(type) { case A: return src.SomeField, nil case *A: return src.SomeField, nil } return nil, nil }, }, "someAnotherField": &graphql.Field{ Name: "someAnotherField", Type: graphql.Int, Resolve: func(p graphql.ResolveParams) (interface{}, error) { switch src := p.Source.(type) { case A: return src.SomeAnotherField, nil case *A: return src.SomeAnotherField, nil } return nil, nil }, }, "andAnotherOne": &graphql.Field{ Name: "andAnotherOne", Type: graphql.String, Resolve: func(p graphql.ResolveParams) (interface{}, error) { switch src := p.Source.(type) { case A: return src.AndAnotherOne, nil case *A: return src.AndAnotherOne, nil } return nil, nil }, }, }, }) 😞
- 8. *.proto gogo stdin stdout GRPC Client GRPC Client Tests GoGo code generation process plugin 1plugin 1 plugin 2 plugin N
- 9. protoc-gen-gogoopsee GRPC Message GraphQL Output Object GraphQL Input Object GRPC Service GraphQL Fields Array GRPC Enum GraphQL Enum Input Object unmarshaler+ GRPC Method Field Resolver X X X
- 10. p.P(`»`, field.GetName(), `": &`, graphQLPkg.Use(), `.Field{`) p.In() p.P(`Type: `, p.graphQLType(message, field, graphQLPkg, schemaPkg), `,`) p.P(`Description: `, fieldGQL, `,`) p.P(`Resolve: func(p `, graphQLPkg.Use(), `.ResolveParams) (interface{}, error) {`) p.In() p.P(`return nil, nil`) p.Out() p.P(`}}`) p.Out() fmt.Println() generated code
- 11. «{{$field.Name}}»: {{gqlPkg}}.Field{ Type: {{call $field.Type}}, Description: {{$field.Description}}, Resolve: func(p {{gqlPkg}}.ResolveParams) (interface{}, error) { return nil, nil } } Generate code using text/template
- 12. GoGo plugin problems • Only two files in output • Generator knows about only one .proto file and can’t make composition • Hard to debug • Option-based configuration
- 13. .proto files parser generate.yaml vendor_path: «./vendor» paths: - «$GOPATH/src» - «./vendor» proto_files: - path : «./a.proto» - … - path: «./b.proto» schema: Query: - field: «a» type: «SERVICE» - field: «b» type: «SERVICE» Parser Query { a : AService, b: BService, } AService { meth1(req:Req) : MethResp, meth2(req:Req) : SomeRes, } BService { meth1(req:Req) : MethResp, } a.proto b.proto Template schema.go ./services/a.go ./services/b.go proto2gql
- 16. Generator responsibilities .proto files GraphQL schema swagger files
- 17. Custom .proto files parser generate.yaml vendor_path: «./vendor» paths: - «$GOPATH/src» - «./vendor» proto_files: - path : «./a.proto» - … - path: «./b.proto» schema: Query: - field: «a» type: «SERVICE» - field: «b» type: «SERVICE» Query { a : AService, b: BService, } AService { meth1(req:Req) : MethResp, meth2(req:Req) : SomeRes, } BService { meth1(req:Req) : MethResp, } Parser a.proto b.proto Template schema.go ./services/a.go ./services/b.go
- 18. Normalizing data generate.yaml vendor_path: «./vendor» paths: - «$GOPATH/src» - «./vendor» proto_files: - path : «./a.proto» - … - path: «./b.proto» schema: Query: - field: «a» type: «SERVICE» - field: «b» type: «SERVICE» Query { a : AService, b: BService, } AService { meth1(req:Req) : MethResp, meth2(req:Req) : SomeRes, } BService { meth1(req:Req) : MethResp, } .proto parser a.proto b.proto Template schema.go ./services/a.go ./services/b.go swagger Parser data normalizer data normalizer swagger1.yml swagger2.yml
- 19. generate.yaml vendor_path: «./» graphql: schemas: … proto2gql: proto_files: - … swagger2gql: swagger_files: - … graphql plugin (knows how to generate graphql schema based on own DTO’s) proto2gql plugin (knows how to convert info about *.proto file into graphql DTO’s) proto2gql swagger2gql plugin (knows how to convert info swagger file into graphql DTO’s) Plugins
- 21. Conclusions • Use templates in code generation • Prepare data for templates in case of a possibility of some other data-source • Choose toolchain that will not frame you