Calling nestjs gRPC service on AWS ECS Fargate, Connection not established - nestjs

Question

I have 2 nestjs microservices deployed to the AWS ECS(Fargate).
Service A exposes HTTP endpoints and works as gateway, and service B is using gRPC with nestjs. Service A calls service B gRPC API.
I’ve deployed both services on AWS ECS (Fargate) and using service discovery for service B. I’ve verified the service discovery name can be resolved with Cloud9 IDE.
Everything works end to end when I run them locally (hit service A’s endpoint and then service would call service B and get expected response). After deployment, I also verified that service B is reachable using postman gRPC request to directly call service B using public IP.
However, in Fargate, when service A tries to call service B, I keep getting Error 14 UNAVAILABLE Connection not established.
Below are how I bootstrap Service B and how I initiate Service B’s client in Service A
Bootstrap service B
async function bootstrap() {
const app: INestMicroservice = await NestFactory.createMicroservice(AppModule, {
transport: Transport.GRPC,
options: {
url: '0.0.0.0:50051',
package: protobufPackage,
protoPath: join('node_modules/services-proto/proto/serviceb.proto'),
},
});
app.useGlobalFilters(new HttpExceptionFilter());
app.useGlobalPipes(new ValidationPipe({ whitelist: true, transform: true }));
await app.listen();
}
bootstrap();
Initiate service B client in service A
imports: [
ClientsModule.register([
{
name:SERVICE_B_NAME,
transport: Transport.GRPC,
options: {
url: process.env.SERVICE_B_URL,
package: SERVICE_B_PACKAGE_NAME,
protoPath: 'node_modules/services-proto/proto/serviceb.proto',
},
},
]),
],
Appreciate any help! Thanks!
I have tested locally and everything works from end to end. I could successfully hit service A’s HTTP endpoint and service successfully invoked service B’s gRPC API.
I’ve verified on AWS Cloud9 IDE that service discovery of service B are successfully resolved.
I’ve make sure inbound rule and outbound rule are set correctly for both security groups of service A and service B.
I’ve tested the service B’s gRPC is reachable with postman gRPC request.