Http Clients Pools Handling

[shalevamit9]

I see in npm docs and GitHub as well the common methods like:

• request
• stream
• pipeline
• connect
• fetch

The question is, for example the simple example of:

const { request } = require('undici')
async function getRequest (port = 3001) {
  // A simple GET request
  const {
    statusCode,
    headers,
    body
  } = await request(`http://localhost:${port}/`)

  const data = await body.text()
  console.log('response received', statusCode)
  console.log('headers', headers)
  console.log('data', data)
}

1. Does the undici package handle the client creation, reuse, and manage pool of clients when using the simple request method?
   I'm asking this as I don't see any hint regarding this in docs. I only see that there's client and clients pool offered by undici but is it managed behind the scenes?
2. Another question if it does handle a connection pool behind the scenes is, how does it handle DNS invalidation?

[metcoder95]

👋

1. By default, it creates a Pool of connections to handle multiple origin
2. It does not; once the DNS resolution is done, the connection will prevail until it goes idle and later dropped or dropped manually for either side of the connection. After that, a new DNS resolution will be done, and from there things like host DNS caching and others plays its part.
   • We are seeking to implement DNS caching, but that still WIP

[shalevamit9]

Hey @metcoder95, thanks for the answer, the first point is very clear. I want to clarify a scenario if it's possible regarding the second point.
Let's take for example the following simple express app that uses undici:

const express = require("express");
const { request } = require("undici");

const app = express();

app.get("/", async (req, res) => {
  const response = await request("http://some-endpoints");

  await response.body.dump();

  res.end();
});

app.listen(3000, () => console.log("up"));

Let's say that this single endpoint keeps getting called without stop and some time after creating the connection, some-endpoints DNS changes. At the moment I have two ideas:

1. Recognize that sort of error and dispose the connection manually.
2. Minimize the idle time so it will dispose automatically.

Am I at the right direction for a current solution?

[metcoder95]

Yes, that approach is correct and the only way to sort that out for the moment. If the DNS changes and the IP comes with it, undici will just fail because the connection might be dropped or not available anymore. Then a new reconnect will be necessary.

As you suggest, you can lower the keepAliveMaxTimeout to reduce the life of the connection and drop it faster (https://undici.nodejs.org/#/docs/api/Client?id=parameter-clientoptions), if you want to have a faster cycle to minimize this possibility.