RestServer and Socket.io

[TheZwieback]

Hi,

I want to implement a WebSocket server on a loopback rest server. As the rest server is based on an express app with a node http server this should be straight forward. Unfortunately I found a minor issue. Accessing the node http server object is not possible in the RestApplication constructor as it is protected inside the RestServer class. I changed the properties on my machine locally and tested the standard deployment and it works as expected:

import { BootMixin } from '@loopback/boot';
import { ApplicationConfig } from '@loopback/core';
import {
  RestExplorerBindings,
  RestExplorerComponent,
} from '@loopback/rest-explorer';
import { RepositoryMixin } from '@loopback/repository';
import { RestApplication } from '@loopback/rest';
import { ServiceMixin } from '@loopback/service-proxy';
import * as path from 'path';
import { MySequence } from './sequence';
import { Server as ioServer, ServerOptions as ioServerOptions, Socket } from "socket.io";
import SocketIOServer = require('socket.io');

export class Bff extends BootMixin(
  ServiceMixin(RepositoryMixin(RestApplication)),
) {
  private ioServer: ioServer;

  constructor(options: ApplicationConfig = {}) {
    super(options);

    // Set up the custom sequence
    this.sequence(MySequence);

    // Set up default home page
    this.static('/', path.join(__dirname, '../public'));

    // Customize @loopback/rest-explorer configuration here
    this.bind(RestExplorerBindings.CONFIG).to({
      path: '/explorer',
    });
    this.component(RestExplorerComponent);

    this.projectRoot = __dirname;
    // Customize @loopback/boot Booter Conventions here
    this.bootOptions = {
      controllers: {
        // Customize ControllerBooter Conventions here
        dirs: ['controllers'],
        extensions: ['.controller.js'],
        nested: true,
      },
    };

    this.ioServer = SocketIOServer();
  }

  async start(): Promise<void> {
    await super.start();
    console.log(this.restServer.listening);
    this.ioServer.attach(this.restServer._httpServer!.server);
    console.log(this.ioServer);
  }
}

Would it be possible to make the base http Server object (this.restServer._httpServer) available through a getter? Using the RestServer instance in the ioServer.attach method does not work.

Thanks and cheers, Christian

[raymondfeng]

@TheZwieback Can you build on top of https://github.com/strongloop/loopback-next/tree/socketio/packages/socketio?

[TheZwieback]

@raymondfeng I looked at the package and it seems to instantiate a new http server to use in its middleware. It would be nice to just use an existing one, i.e. like the rest server described above. I do not need to expose the socket.io server through dedicated controller endpoints, instead I want the regular http rest endpoints to deliver progress updates through socket.io. Maybe a mixin would be possible to enhance the RestServer cleanly?

[gemyero]

@TheZwieback I write some code to solve this problem. I write a mixin called RevealServerMixin which can be invoked with RestApplication class and it do it. Here is the code.

// RevealServerMixin
import { Constructor } from '@loopback/core';
import { CustomRestComponent } from '../services/CustomRestComponent';
import { CustomRestServer } from '../services/CustomRestServer';

export function RevealServerMixin<T extends Constructor<any>>(
  BaseClass: T,
) {
  class Subclass extends BaseClass {
    constructor(...args: any[]) {
      super(...args);

      this.unbind('components.RestComponent');
      this.unbind('servers.RestServer');

      this.component(CustomRestComponent);
    }

    get restServer(): CustomRestServer {
      return this.getSync('servers.CustomRestServer');
    }
  }
  return Subclass;
}

// CustomRestComponent
import { RestComponent } from '@loopback/rest';
import { Constructor, Server } from '@loopback/core';
import { CustomRestServer } from './CustomRestServer';

export class CustomRestComponent extends RestComponent {
  servers: {
    [name: string]: Constructor<Server>
  } = {
    CustomRestServer,
  };
}

// CustomRestServer
import { RestServer } from '@loopback/rest';
import { HttpServer } from '@loopback/http-server';

export class CustomRestServer extends RestServer {
  get httpServer(): HttpServer | undefined {
    return this._httpServer;
  }
}

And in application.ts

export class MyApplication extends RevealServerMixin(RestApplication)
) {}

[alexkander]

Maybe this can help #4044

[stale[bot]]

This issue has been marked stale because it has not seen activity within six months. If you believe this to be in error, please contact one of the code owners, listed in the CODEOWNERS file at the top-level of this repository. This issue will be closed within 30 days of being stale.

[stale[bot]]

This issue has been closed due to continued inactivity. Thank you for your understanding. If you believe this to be in error, please contact one of the code owners, listed in the CODEOWNERS file at the top-level of this repository.