Debugging logs

const handler: ExportedHandler = {
  async fetch(request, env, ctx) {
    // Service configured to receive logs
    const LOG_URL = "https://log-service.example.com/";

    async function postLog(data) {
      return await fetch(LOG_URL, {
        method: "POST",
        body: data,
      });
    }

    let response;

    try {
      response = await fetch(request);
      if (!response.ok && !response.redirected) {
        const body = await response.text();
        throw new Error(
          "Bad response at origin. Status: " +
            response.status +
            " Body: " +
            // Ensure the string is small enough to be a header
            body.trim().substring(0, 10)
        );
      }
    } catch (err) {
      // Without ctx.waitUntil(), your fetch() to Cloudflare's
      // logging service may or may not complete
      ctx.waitUntil(postLog(err.toString()));
      const stack = JSON.stringify(err.stack) || err;
      // Copy the response and initialize body to the stack trace
      response = new Response(stack, response);
      // Add the error stack into a header to find out what happened
      response.headers.set("X-Debug-stack", stack);
      response.headers.set("X-Debug-err", err);
    }
    return response;
  },
};

export default handler;