hang_heartbeat.js

const http = require("http");
const vm = require("vm");
const fs = require("fs");

function scheduleLoop(schedule) {
  function loop(sum = 0) {
    schedule(() => loop(doSomeWork(sum)));
  }
  schedule(loop);
}

function promiseLoop(Promise) {
  scheduleLoop(fn => Promise.resolve().then(fn));
}

http
  .createServer((req, res) => {
    switch (req.url) {
      case "/ping":
        res.statusCode = 200;
        res.end("pong");
        break;
      case "/tick":
        scheduleLoop(process.nextTick);
        break;
      case "/immediate":
        scheduleLoop(setImmediate);
        break;
      case "/timeout":
        scheduleLoop(fn => setTimeout(fn, 0));
        break;
      case "/asyncfn":
        scheduleLoop(async fn => await fn());
        break;
      case "/promise":
        promiseLoop(Promise);
        break;
      case "/rsvp":
        promiseLoop(require("rsvp").Promise);
        break;
      case "/rsvpvm":
        promiseLoop(vmContext("rsvp").RSVP.Promise);
        break;
      default:
        res.statusCode = 404;
        res.end("not found");
    }
  })
  .listen(4321)
  .on("listening", () => {
    console.log("ping               http://localhost:4321/ping");
    console.log("nextTick loop      http://localhost:4321/tick");
    console.log("immediate loop     http://localhost:4321/immediate");
    console.log("timeout 0 loop     http://localhost:4321/timeout");
    console.log("async func loop    http://localhost:4321/asyncfn");
    console.log("promise loop       http://localhost:4321/promise");
    console.log("RSVP loop          http://localhost:4321/rsvp");
    console.log("RSVP vm loop       http://localhost:4321/rsvpvm");
  })
  .on("error", e => console.error("%O", e));

function vmContext(mod) {
  const filename = require.resolve(mod);
  const code = fs.readFileSync(filename, "utf8");
  const script = new vm.Script(code, {
    filename
  });
  const context = vm.createContext({
    setTimeout
  });
  script.runInContext(context);
  return context;
}

function doSomeWork(sum = 0) {
  let array = [];
  for (let i = 0; i < 10000; i++) {
    array.push(i);
  }
  return array.reduce((a, b) => a + b, sum);
}