grpc

What is grpc?

The grpc npm package is a Node.js library for making and handling remote procedure calls (RPC) using the gRPC framework. It allows for efficient communication between services, supports multiple programming languages, and provides features like load balancing, authentication, and more.

What are grpc's main functionalities?

Creating a gRPC Server

This code demonstrates how to create a basic gRPC server in Node.js. It loads a .proto file, defines a service, and starts the server to listen for incoming requests.

const grpc = require('grpc');
const protoLoader = require('@grpc/proto-loader');
const packageDefinition = protoLoader.loadSync('path/to/your/protofile.proto', {});
const protoDescriptor = grpc.loadPackageDefinition(packageDefinition);
const yourService = protoDescriptor.yourService;

function yourFunction(call, callback) {
  callback(null, { message: 'Hello ' + call.request.name });
}

const server = new grpc.Server();
server.addService(yourService.service, { yourFunction: yourFunction });
server.bind('127.0.0.1:50051', grpc.ServerCredentials.createInsecure());
server.start();

Creating a gRPC Client

This code demonstrates how to create a gRPC client in Node.js. It connects to a gRPC server, makes a request, and handles the response.

const grpc = require('grpc');
const protoLoader = require('@grpc/proto-loader');
const packageDefinition = protoLoader.loadSync('path/to/your/protofile.proto', {});
const protoDescriptor = grpc.loadPackageDefinition(packageDefinition);
const yourService = protoDescriptor.yourService;

const client = new yourService('localhost:50051', grpc.credentials.createInsecure());

client.yourFunction({ name: 'World' }, (error, response) => {
  if (!error) {
    console.log('Greeting:', response.message);
  } else {
    console.error(error);
  }
});

Streaming RPC

This code demonstrates how to implement a streaming RPC in a gRPC server. It handles incoming stream data and sends responses back to the client.

const grpc = require('grpc');
const protoLoader = require('@grpc/proto-loader');
const packageDefinition = protoLoader.loadSync('path/to/your/protofile.proto', {});
const protoDescriptor = grpc.loadPackageDefinition(packageDefinition);
const yourService = protoDescriptor.yourService;

function yourStreamFunction(call) {
  call.on('data', (request) => {
    console.log('Received:', request);
    call.write({ message: 'Hello ' + request.name });
  });
  call.on('end', () => {
    call.end();
  });
}

const server = new grpc.Server();
server.addService(yourService.service, { yourStreamFunction: yourStreamFunction });
server.bind('127.0.0.1:50051', grpc.ServerCredentials.createInsecure());
server.start();

Other packages similar to grpc

grpc-web

The grpc-web package allows gRPC to be used in web applications. It provides a JavaScript client library that can communicate with gRPC services from the browser. This package is useful for integrating gRPC with frontend applications, whereas the grpc package is primarily focused on server-side and backend communication.

README

Node.js gRPC Library

Status

Alpha : Ready for early adopters

Prerequisites

This requires node to be installed. If you instead have the nodejs executable on Debian, you should install the nodejs-legacy package.

Installation

1. Clone the grpc repository.
2. Follow the instructions in the INSTALL file in the root of that repository to install the C core library that this package depends on.
3. Run npm install.

Tests

To run the test suite, simply run npm test in the install location.

API

This library internally uses ProtoBuf.js, and some structures it exports match those exported by that library

If you require this module, you will get an object with the following members

function load(filename)

Takes a filename of a Protocol Buffer file, and returns an object representing the structure of the protocol buffer in the following way:

• Namespaces become maps from the names of their direct members to those member objects
• Service definitions become client constructors for clients for that service. They also have a service member that can be used for constructing servers.
• Message definitions become Message constructors like those that ProtoBuf.js would create
• Enum definitions become Enum objects like those that ProtoBuf.js would create
• Anything else becomes the relevant reflection object that ProtoBuf.js would create

function loadObject(reflectionObject)

Returns the same structure that load returns, but takes a reflection object from ProtoBuf.js instead of a file name.

function buildServer(serviceArray)

Takes an array of service objects and returns a constructor for a server that handles requests to all of those services.

status

An object mapping status names to status code numbers.

callError

An object mapping call error names to codes. This is primarily useful for tracking down certain kinds of internal errors.

Credentials

An object with factory methods for creating credential objects for clients.

ServerCredentials

An object with factory methods fro creating credential objects for servers.