Koa 2 router how to make a long poll request

Question

I want to make a long pooling request. So I want to take a request and send a response after some delay. Is it possible?

I'm trying to use the async/await synax but it's isn't working for me (I got an error 404 on the client)

many thanks for any help.

Here is my server

import 'babel-polyfill';
import Koa from 'koa';
import Router from "koa-router";

import fs from "fs";


const router = new Router();

const convert = require('koa-convert')
const serve = require("koa-static");

const app = new Koa();


router
  .get('/*', async function (ctx, next) {



            ctx.response.type = 'text/html; charset=utf-8';

            /* await (() => {
                setTimeout( () => {ctx.body = fs.readFileSync(__dirname + "/public/index.html")}, 1000)
            })(); */

            //ctx.body = fs.readFileSync(__dirname + "/public/index.html");


  })

app.use(convert(serve(`${__dirname}/public`)))
app.use(router.routes()).use(router.allowedMethods());

app.listen(3000);

Answer 1

Generally, yes. This is possible.

The problem in your code is, that await is entierly based on promises. So your timeout function needs to be encapsulated into a promise. Something like this could work:

...
function delayed(ctx, ms) {
    return new Promise((resolve, reject) => {
        setTimeout(function() {
            ctx.body = fs.readFileSync(__dirname + "/public/index.html")
            resolve();
        }, ms);
    })
}

router.get('/*', async function (ctx, next) {
    ctx.response.type = 'text/html; charset=utf-8';
    await delayed(ctx, 1000);
})
...