Next.js SItemap route with streaming (requires Node 18+)

route.ts

import { SitemapStream, EnumChangefreq } from "sitemap";

import { getAllPosts } from "~/data";

import { Readable } from "node:stream";

async function* getSitemapUrls(request: Request) {
  const url = new URL(request.url);
  const origin = `${url.protocol}//${url.host}`;

  const buildUrl = (path: string) => `${origin}${path}`;

  yield {
    url: buildUrl("/"),
    changefreq: EnumChangefreq.DAILY,
    priority: 0.7,
  };

  for (const post of await getAllPosts()) {
    yield {
      url: buildUrl(`/posts/${post.slug}`),
      changefreq: EnumChangefreq.DAILY,
      priority: 0.7,
    };
  }
}

export async function GET(request: Request) {
  try {
    const smStream = new SitemapStream();

    Readable.from(getSitemapUrls(request)).pipe(smStream);

    // smStream is a node stream, so we need to turn it into a web platform one.
    const reader = Readable.toWeb(smStream).getReader();
    const encoder = new TextEncoder();

    const stream = new ReadableStream({
      async pull(controller) {
        const { value, done } = await reader.read();

        if (done) {
          return controller.close();
        }

        controller.enqueue(encoder.encode(value));
      },
    });

    return new Response(stream, {
      headers: {
        "Content-Type": "application/xml",
      },
      status: 200,
    });
  } catch (e) {
    console.error(e);

    return new Response("", {
      status: 500,
    });
  }
}