Building a Microservice with gRPC

gRPC Basics

This lesson explains the main concept clearly with beginner-friendly examples and background so you can learn why the code works.

Install protobuf tools:

$ go install google.golang.org/protobuf/cmd/protoc-gen-go@latest
$ go install google.golang.org/grpc/cmd/protoc-gen-go-grpc@latest

Define a service (proto/todo.proto)

syntax = "proto3";
package todo;

service TodoService {
  rpc Create (CreateRequest) returns (CreateResponse);
  rpc List   (ListRequest)   returns (ListResponse);
}

message Todo { int32 id = 1; string title = 2; bool done = 3; }
message CreateRequest { string title = 1; }
message CreateResponse { Todo todo = 1; }
message ListRequest {}
message ListResponse { repeated Todo todos = 1; }

Generate Go code:

$ protoc --go_out=. --go-grpc_out=. proto/todo.proto

Server implementation

type server struct { todo.UnimplementedTodoServiceServer; store map[int32]*todo.Todo; next int32 }

func (s *server) Create(ctx context.Context, req *todo.CreateRequest) (*todo.CreateResponse, error) {
    s.next++
    t := &todo.Todo{Id: s.next, Title: req.Title, Done: false}
    s.store[t.Id] = t
    return &todo.CreateResponse{Todo: t}, nil
}

func (s *server) List(ctx context.Context, _ *todo.ListRequest) (*todo.ListResponse, error) {
    resp := &todo.ListResponse{}
    for _, t := range s.store { resp.Todos = append(resp.Todos, t) }
    return resp, nil
}

func main() {
    lis, _ := net.Listen("tcp", ":50051")
    s := grpc.NewServer()
    todo.RegisterTodoServiceServer(s, &server{store: make(map[int32]*todo.Todo)})
    log.Fatal(s.Serve(lis))
}

Client stub

conn, _ := grpc.Dial("localhost:50051", grpc.WithInsecure())
client := todo.NewTodoServiceClient(conn)
resp, _ := client.Create(context.Background(), &todo.CreateRequest{Title: "Buy milk"})
fmt.Println(resp.Todo)