When is sitemap() invoked and best practices?

[ben519]

I'm reading the docs for sitemap. It states

You can use the sitemap.(js|ts) file convention to programmatically generate a sitemap by exporting a default function that returns an array of URLs.

However, it doesn't say anything about when this function is invoked. I assume it's invoked at build time, but this raises some issues / questions:

1. What if I don't rebuild my site for weeks? The sitemap will become outdated as my site's users add new pages. What's the best way to overcome this issue?
2. Presumably, every time I build my site, sitemap() is invoked. In my case, it'll fetch every record in a large database table of posts. This could become costly if I have to rebuild my site multiple times in one day.

Any advice on this front would be appreciated!

[spirituelle]

Use cach system to revalidate your data when needed.
your request should look like this :
const res = await fetch(${process.env.BACKEND_URL}/api/site-map, { next: { tags: [ 'sitemap'] }});
and then you have to set up a revalidation system under /app/api/revalidate/route.ts, it should look like this
import { revalidateTag } from 'next/cache'
import { NextRequest, NextResponse } from 'next/server'

export async function POST(request: NextRequest) {
const secret = request.nextUrl.searchParams.get('secret')
const tag = request.nextUrl.searchParams.get('tag')

if (secret !== process.env.REVALIDATION_SECRET_TOKEN) {
return NextResponse.json({ message: 'Invalid secret' }, { status: 401 })
}

if (!tag) {
return NextResponse.json({ message: 'Missing tag param' }, { status: 400 })
}

revalidateTag(tag)

return NextResponse.json({ revalidated: true, now: Date.now() })
then whenever there new data or once a day or whatever you can send a POST request to yourwebsite/api/revalidate with the tag you want to revalidate (in this case sitemap) and the secret.
i hope this helpfull. it work fine for me