Defining gRPC APIs with Protobuf - Part 2

In Part 1, we set up our project structure. Now, we’ll:
✅ Define User and Order APIs
✅ Generate gRPC code from .proto files.

We have created apis folder so lets navigate to that folder and define our apis there.

cd ecom-grpc/apis

Note: Please replace the github user name and repo in each of the following folder

Step 1: Install Protobuf Compiler

Before writing .proto files, install protoc:

🔹 Mac (Homebrew)

brew install protobuf

🔹 Ubuntu/Linux

sudo apt update && sudo apt install -y protobuf-compiler

🔹 Windows

Download from protobuf releases.

Verify installation:

protoc --version

Step 2: Define User Service API

create user/v1/user.proto file in apis repo

mkdir -p user/v1/
touch user/v1/user.proto

syntax = "proto3";

package user.v1;

option go_package = "github.com/lakhansamani/ecom-grpc-apis/user/v1";

// User Service definition
service UserService {
    // Register API to register a new user
    // Permission: none
    rpc Register(RegisterRequest) returns (RegisterResponse);
    // Login API to login a user
    // Permission: none
    rpc Login(LoginRequest) returns (LoginResponse);
    // Me API to get user details
    // Permission: authenticated user
    rpc Me(MeRequest) returns (MeResponse);
}

// User model
message User {
    string id = 1;
    string name = 2;
    string email = 3;
}

// Register API
message RegisterRequest {
    string name = 1;
    string email = 2;
    string password = 3;
}

message RegisterResponse {
    string user_id = 1;
}

// Login API
message LoginRequest {
    string email = 1;
    string password = 2;
}

message LoginResponse {
    string token = 1;
}

// Me API (token will be taken from gRPC metadata)
message MeRequest {}

message MeResponse {
    User user = 1;
}

New API methods

• Register → Registers a new user and returns a JWT token.
• Login → Authenticates a user and returns a JWT token.
• Me → Returns user details using the JWT token.

🔹 Step 3: Define Order Service API

create order/v1/order.proto file in apis repo

mkdir -p order/v1/
touch order/v1/order.proto

syntax = "proto3";

package order.v1;

option go_package = "github.com/lakhansamani/ecom-grpc-apis/order/v1";

service OrderService {
    // CreateOrder API to create a new order
    // Permission: authenticated user
    rpc CreateOrder(CreateOrderRequest) returns (CreateOrderResponse);
    // GetOrder API to get order details
    // Permission: authenticated user who created the order
    rpc GetOrder(GetOrderRequest) returns (GetOrderResponse);
}

// Order model
message Order {
    string id = 1;
    string user_id = 2;
    string product = 3;
    int32 quantity = 4;
    double unit_price = 5;
}

// CreateOrder request API
message CreateOrderRequest {
    string user_id = 1;
    string product = 2;
    int32 quantity = 3;
    double price = 4;
}

// CreateOrder response API
message CreateOrderResponse {
    Order order = 1;
}

// GetOrder request API
message GetOrderRequest {
    string id = 1;
}

// GetOrder response API
message GetOrderResponse {
    Order order = 1;
}

New API methods

• CreateOrder - to create order
• GetOrder - to get order information

🔹 Step 4: Generate gRPC Code

To simplify the process lets create a Makefile at the root of apis repo which we can run to generate the go-grpc code.

touch Makefile

all: build
build:
    protoc --go_out=. --go_opt=paths=source_relative --go-grpc_out=require_unimplemented_servers=false:. --go-grpc_opt=paths=source_relative user/v1/user.proto
    protoc --go_out=. --go_opt=paths=source_relative --go-grpc_out=require_unimplemented_servers=false:. --go-grpc_opt=paths=source_relative order/v1/order.proto

Run make command to generate the files and push to github.

Code Link

• Github APIs repo

🎯 Next Steps

• 🚀 Now that we have the User & Order Service protobuf, in Part 3, we will:
• ✅ Implement User Service.
• ✅ Implement Order Service.

Stay tuned! 🚀