Wrong concurrency model

[manyuanrong]

This is a piece of code from Oak:

https://github.com/oakserver/oak/blob/master/application.ts#L25-L35

This incorrectly uses await for each request. As a result, requests cannot be executed in parallel, but are executed serially. If two requests are sent in succession, each of which takes 10s, eventually all requests will be completed in 20s instead of all being completed at the same time in 10s

import { Application } from "https://deno.land/x/oak/mod.ts";
const app = new Application();
app.use(async ctx => {
  await new Promise(resolve => setTimeout(resolve, 10000));
  ctx.response.body = "Hello World!";
});
await app.listen({ port: 8000 });

[manyuanrong]

My example seems wrong. I also got the same result using setTimeout in Node.js

[manyuanrong]

I encountered the problem of deadlock, and I guess it was caused by concurrency, but it wasn't. But my code can respond normally in std / http / server. Deadlocked in oak

Deadlocked

import { Application } from "https://deno.land/x/oak/mod.ts";
const app = new Application();
app.use(async ctx => {
  console.log(ctx.request.url);
  if (ctx.request.url === "/ssr") {
    await fetch("http://localhost:8000/hello")
      .then(res => res.text())
      .then(text => {
        ctx.response.body = text;
      });
  } else {
    ctx.response.body = "Hello World!";
  }
});
await app.listen({ port: 8000 });

It is normal

import { serve } from "https://deno.land/std/http/server.ts";
const body = new TextEncoder().encode("Hello World\n");
for await (const req of serve(":8000")) {
  console.log(req.url);
  if (req.url === "/ssr") {
    fetch("http://localhost:8000/hello")
      .then(res => res.text())
      .then(text => {
        req.respond({ body: text });
      });
  } else {
    req.respond({ body });
  }
}

[Qard]

Yep, that should really spin off another handleRequest async function which it uses catch(...) on instead of awaiting it. That’d allow it to run in the background.