NestJS gRPC Client

A modern, production-ready gRPC client library for NestJS with full streaming support, smart retry strategies, and comprehensive TypeScript types.

Quick Start

npm install @nam088/nestjs-grpc

// app.module.ts
import { GrpcClientModule } from '@nam088/nestjs-grpc';

@Module({
  imports: [
    GrpcClientModule.forRoot({
      services: [{
        protoPath: './proto/user.proto',
        package: 'user',
        serviceName: 'UserService',
        url: 'localhost:50051'
      }],
      retry: {
        maxAttempts: 3,
        initialBackoff: 1000,
        retryableCodes: [grpc.status.UNAVAILABLE]
      },
      logLevel: 'DEBUG'
    })
  ]
})
export class AppModule {}

// user.service.ts
@Injectable()
export class UserService {
  constructor(private grpc: GrpcClientService) {}

  getUser(id: string) {
    return this.grpc.call({
      package: 'user',
      service: 'UserService',
      method: 'GetUser',
      request: { id }
    });
  }
}

Features

Core Capabilities

• Full gRPC Support - Unary, server streaming, client streaming, bidirectional streaming
• RxJS Integration - Native Observable support with powerful operators
• TypeScript First - Complete type safety with generics and JSDoc
• Multi-Service - Manage multiple gRPC services in one module

Production Ready

• Smart Retry - Exponential/linear/fixed backoff with jitter
• Interceptors - Built-in logging, custom middleware support
• Exception Mapping - Automatic gRPC → HTTP status code conversion
• Well Tested - 46 unit tests, 87%+ code coverage

Developer Experience

• Object-Based API - Clean, readable method calls
• Comprehensive Docs - Full JSDoc with examples
• NestJS Native - Seamless integration with NestJS ecosystem

Usage Examples

Basic Call

this.grpc.call({
  package: 'user',
  service: 'UserService',
  method: 'GetUser',
  request: { id: '123' },
  timeout: 5000 // Optional timeout in ms
}).subscribe(user => console.log(user));

With RxJS Operators

this.grpc.call({ ... }).pipe(
  timeout(5000),
  map(user => user.email),
  catchError(err => of(null))
).subscribe();

Server Streaming

this.grpc.callServerStream({
  package: 'chat',
  service: 'ChatService',
  method: 'StreamMessages',
  request: { roomId: 'room1' }
}).subscribe(message => console.log(message));

Client Streaming

const { stream, response } = this.grpc.callClientStream({
  package: 'upload',
  service: 'FileService',
  method: 'UploadFile'
});

// Send data
stream.next({ chunk: data1 });
stream.next({ chunk: data2 });
stream.complete();

// Get response
response.subscribe(result => console.log(result));

Bidirectional Streaming

const { stream, response } = this.grpc.callBidiStream({
  package: 'chat',
  service: 'ChatService',
  method: 'Chat'
});

// Send and receive simultaneously
stream.next({ text: 'Hello' });
response.subscribe(msg => console.log(msg));

Smart Retry

import { RetryStrategy } from '@nam088/nestjs-grpc';

this.grpc.call({ ... }).pipe(
  RetryStrategy.retry({
    maxAttempts: 3,
    backoffStrategy: 'exponential',
    retryableCodes: [grpc.status.UNAVAILABLE],
    initialBackoff: 1000,
    maxBackoff: 5000,
    backoffMultiplier: 2,
    enableJitter: true
  })
).subscribe();

With Interceptors

// app.module.ts
GrpcClientModule.forRoot({
  services: [...],
  interceptors: [LoggingInterceptor, MetricsInterceptor]
})

// Custom interceptor
@Injectable()
export class MetricsInterceptor implements GrpcInterceptor {
  intercept(options, next) {
    const start = Date.now();
    return next().pipe(
      tap(() => this.recordMetric(Date.now() - start))
    );
  }
}

Exception Handling

@Catch(GrpcException)
export class GrpcExceptionFilter implements ExceptionFilter {
  catch(exception: GrpcException, host: ArgumentsHost) {
    const response = host.switchToHttp().getResponse();
    response.status(exception.getStatus()).json({
      error: exception.details,
      code: exception.code
    });
  }
}

API Reference

GrpcClientModule

GrpcClientModule.forRoot({
  services: GrpcServiceConfig[],
  interceptors?: GrpcInterceptor[],
  isGlobal?: boolean,
  retry?: RetryConfig,
  logLevel?: 'DEBUG' | 'INFO' | 'WARN' | 'ERROR'
})

GrpcClientService

| Method | Description | Returns | |--------|-------------|---------| | call() | Unary call | Observable<TResponse> | | callServerStream() | Server streaming | Observable<TResponse> | | callClientStream() | Client streaming | { stream, response } | | callBidiStream() | Bidirectional | { stream, response } |

RetryStrategy

RetryStrategy.retry({
  maxAttempts?: number,           // Default: 3
  initialBackoff?: number,        // Default: 1000
  maxBackoff?: number,            // Default: 5000
  backoffStrategy?: 'exponential' | 'linear' | 'fixed',
  backoffMultiplier?: number,     // Default: 2
  retryableCodes?: grpc.status[],
  enableJitter?: boolean          // Default: true
})

Configuration

Basic Setup

GrpcClientModule.forRoot({
  services: [{
    protoPath: './proto/user.proto',
    package: 'user',
    serviceName: 'UserService',
    url: 'localhost:50051'
  }]
})

Multiple Services

GrpcClientModule.forRoot({
  services: [
    {
      protoPath: './proto/user.proto',
      package: 'user',
      serviceName: 'UserService',
      url: 'localhost:50051'
    },
    {
      protoPath: './proto/order.proto',
      package: 'order',
      serviceName: 'OrderService',
      url: 'localhost:50052'
    }
  ],
  isGlobal: true
})

With Credentials

import * as grpc from '@grpc/grpc-js';

GrpcClientModule.forRoot({
  services: [{
    protoPath: './proto/user.proto',
    package: 'user',
    serviceName: 'UserService',
    url: 'api.example.com:443',
    credentials: grpc.credentials.createSsl()
  }]
})

Testing

describe('UserService', () => {
  let service: UserService;
  let grpcClient: GrpcClientService;

  beforeEach(async () => {
    const module = await Test.createTestingModule({
      imports: [GrpcClientModule.forRoot({ services: [...] })],
      providers: [UserService]
    }).compile();

    service = module.get<UserService>(UserService);
    grpcClient = module.get<GrpcClientService>(GrpcClientService);
  });

  it('should get user', async () => {
    const result = await lastValueFrom(service.getUser('123'));
    expect(result).toBeDefined();
  });
});

Migration Guide

From @grpc/grpc-js

// Before
const client = new UserServiceClient('localhost:50051');
client.getUser({ id: '123' }, (err, response) => {
  if (err) throw err;
  console.log(response);
});

// After
this.grpc.call({
  package: 'user',
  service: 'UserService',
  method: 'GetUser',
  request: { id: '123' }
}).subscribe({
  next: response => console.log(response),
  error: err => console.error(err)
});

Best Practices

1. Use Retry for Production

   this.grpc.call({ ... }).pipe(
     RetryStrategy.retry({ maxAttempts: 3 })
   )

2. Add Timeouts

   this.grpc.call({ ... }).pipe(timeout(5000))

3. Handle Errors Gracefully

   this.grpc.call({ ... }).pipe(
     catchError(err => {
       this.logger.error(err);
       return of(defaultValue);
     })
   )

4. Use Interceptors for Cross-Cutting Concerns

   // Logging, metrics, tracing
   GrpcClientModule.forRoot({
     interceptors: [LoggingInterceptor, MetricsInterceptor]
   })

License

MIT © 2025

Links

• GitHub Repository
• npm Package
• Issue Tracker
• gRPC Documentation
• NestJS Documentation