Logtail flush in NextJS api endpoint

index.js

// Next.js API route support: https://nextjs.org/docs/api-routes/introduction

import { Node as Logtail } from '@logtail/js';

const logger = new Logtail(process.env.LOGTAIL_SOURCE_TOKEN);

export default async function handler(req, res) {
  const user = {
    id: 123,
    name: 'John Doe',
  };

  logger.info(
    'Handling a request to /api/hello',
    { user } // you can log structured data
  );

  res.status(200).json({ name: user.name })

  await flush(logger, 1000)
}

const flush = async (l, timeout) => {
  await condition(() => l.logged() === l.synced(), timeout)
}

const sleep = (timeout) => {
  return new Promise((resolve) => {
    setTimeout(resolve, timeout)
  })
}

const condition = (fn, timeout) => {
  if (timeout) {
    return await Promise.race([sleep(timeout).then(() => false), conditionInner(fn).then(() => true)]);
  }
  return conditionInner(fn);
}

const tryUnblockCondition = (fn, resolve) => {
  // Eager evaluation
  if (fn()) {
    resolve();
    return;
  }

  setTimeout(() => {
    tryUnblockCondition(fn, resolve)
  }, 5)
}

const conditionInner = async (fn) => {
  return new Promise((resolve) => {
    tryUnblockCondition(fn, resolve)
  });
}