connection: 'close' in request headers despite the docs

[chris-tse]

Summary

According to this page in the docs, Keep-Alive should be enabled by default.

However, for the fetch calls coming from my API routes, neither explicitly setting that option in my next.config.js, nor setting the header explicitly in my fetch call headers and passing keepalive: true to the fetch options are able to force this to be true.

Is this a known quirk of using server-side fetch?

Additional information

// /api/route
const response = await fetch(url, {
  headers: new Headers({
    Host: 'hostiamfetchingfrom.com',
    Accept: 'text/html,application/xhtml+xml,application/xml;q=0.9,image/avif,image/webp,*/*;q=0.8',
    'Accept-Language': 'en-US,en;q=0.5',
    Connection: 'keep-alive',
    'Upgrade-Insecure-Requests': '1',
    'sec-fetch-mode': 'cors',
    'accept-encoding': 'gzip, deflate',
  }),
  keepalive: true,
})


```js
// next.config.js
const config = {
  httpAgentOptions: {
    keepAlive: true,
  },
}

Example

No response

[icyJoseph]

Looks like it is indeed the native Node.js fetch (which is based on undici) that is doing that:

• https://github.com/nodejs/node/blob/3db54912fa2e4a696d4e2ec27dfb2aeecfc65191/deps/undici/src/lib/web/fetch/index.js#L1435-L1437

  if (contentLength != null && httpRequest.keepalive) {
    // NOTE: keepalive is a noop outside of browser context.
  }

These threads have more interesting takes:

• native fetch api does not respect keepalive parameter in RequestInit nodejs/undici#2169 (comment)
• `keepalive` with body being async generator nodejs/undici#2372 (comment)