content: |

🚀 Node.js gRPC Microservice — User Service

A simple and clean gRPC-based microservice built with Node.js, showcasing how to fetch user details with high performance and low latency.

🔍 What is gRPC?

gRPC (Google Remote Procedure Call) is a high-performance, open-source RPC framework that allows services to communicate efficiently, using:

• 🚄 HTTP/2 (bi-directional streaming, multiplexing)

• 📦 Protocol Buffers (Protobuf) for fast, typed serialization

• 🧠 Contract-first design with .proto files

  ✅ gRPC vs REST

  Feature	REST (Express.js)	gRPC (Node.js)
  Protocol	HTTP/1.1	HTTP/2
  Data Format	JSON (text-based)	Protobuf (binary, compact)
  Contract	Swagger (optional)	.proto (enforced)
  Speed	Slower	🚀 Faster (10x+)
  Streaming	Manual (WebSockets)	Native, full-duplex streaming
  Best for	Public APIs	Microservices/internal services

  📁 Project Structure

  grpc-user-service/
  ├── protos/
  │   └── user.proto
  ├── src/
  │   ├── server/
  │   │   ├── index.js
  │   │   ├── service.js
  │   │   └── loader.js
  │   ├── client/
  │   │   ├── index.js
  │   │   └── loader.js
  │   └── config/
  │       └── grpc.js
  ├── package.json
  └── README.md
  

  🔁 Request Flow

  Client (index.js)
     │
     └──▶ Calls GetUser({ id: "123" })
            ↓
       Client Stub (loader.js)
            ↓
     Sends Protobuf request via HTTP/2
            ↓
       Server receives request
            ↓
       Server Handler (service.js)
            ↓
     Processes and returns UserResponse
            ↓
       Client receives response
     ◀── Logs or uses returned data
  

  Code

files:
  - path: protos/user.proto
    content: |
      syntax = "proto3";

      package user;

      service UserService {
        rpc GetUser (UserRequest) returns (UserResponse);
      }

      message UserRequest {
        string id = 1;
      }

      message UserResponse {
        string name = 1;
        string email = 2;
      }

  - path: src/server/index.js
    content: |
      const server = require('./loader');
      server.start();

  - path: src/server/loader.js
    content: |
      const grpc = require('@grpc/grpc-js');
      const protoLoader = require('@grpc/proto-loader');
      const { implementUserService } = require('./service');

      const PROTO_PATH = __dirname + '/../../protos/user.proto';
      const packageDef = protoLoader.loadSync(PROTO_PATH);
      const userProto = grpc.loadPackageDefinition(packageDef).user;

      const server = new grpc.Server();
      server.addService(userProto.UserService.service, implementUserService());

      exports.start = () => {
        server.bindAsync('0.0.0.0:50051', grpc.ServerCredentials.createInsecure(), () => {
          console.log('✅ gRPC Server started on 0.0.0.0:50051');
          server.start();
        });
      };

  - path: src/server/service.js
    content: |
      exports.implementUserService = () => ({
        GetUser: (call, callback) => {
          const { id } = call.request;
          console.log('User ID:', id);
          callback(null, {
            name: "Amar Kumar",
            email: "amar@example.com"
          });
        }
      });

  - path: src/client/index.js
    content: |
      const client = require('./loader');

      client.GetUser({ id: "123" }, (err, res) => {
        if (err) console.error(err);
        else console.log('🧾 Response:', res);
      });

  - path: src/client/loader.js
    content: |
      const grpc = require('@grpc/grpc-js');
      const protoLoader = require('@grpc/proto-loader');

      const PROTO_PATH = __dirname + '/../../protos/user.proto';
      const packageDef = protoLoader.loadSync(PROTO_PATH);
      const userProto = grpc.loadPackageDefinition(packageDef).user;

      module.exports = new userProto.UserService(
        'localhost:50051',
        grpc.credentials.createInsecure()
      );

  - path: src/config/grpc.js
    content: |
      module.exports = {
        GRPC_PORT: '0.0.0.0:50051',
        GRPC_CREDENTIALS: require('@grpc/grpc-js').ServerCredentials.createInsecure()
      };

  ## ⚙️ Setup & Run

  ```bash
  yarn install
  node src/server/index.js   # Start server
  node src/client/index.js   # Run client
  ```

  ## ✅ Sample Response

  ```json
  {
    "name": "Amar Kumar",
    "email": "amar@example.com"
  }
  ```