Calling Sentry.flush() with @sentry/node always throws an exception on Next.js API endpoints

[Vadorequest]

• Review the documentation: https://docs.sentry.io/
• Search for existing issues: https://github.com/getsentry/sentry-javascript/issues
• Use the latest release: https://github.com/getsentry/sentry-javascript/releases
• Provide a link to the affected event from your Sentry account

Package + Version

• @sentry/browser 6.3.6
• @sentry/node 6.3.6
• raven-js
• raven-node (raven for node)
• other:

Version:

0.0.0

Description

It's recommended by Next.js to call Sentry.flush() manually, before returning an HTTP response from API endpoints.

But, it doesn't work so well. When calling the API endpoint, it doesn't send the error to Sentry and fails with [flushSafe] An exception was thrown while running Sentry.flush(). (see implementation below)

The timeout being used is 5000, which is more than what's recommended (2000).

What's also weird is that I wasn't flushing before and it was working (at least sometimes) but now it always fails.

2021-06-24T20:33:32.151Z [modules/core/amplitude/amplitudeServerClient] Logging Amplitude event "api-invoked" with properties: { apiEndpoint: 'error' }
2021-06-24T20:33:52.953Z	3751ccb9-311e-4e5d-87b1-6b1a1aa04ce9	ERROR	2021-06-24T20:33:52.397Z [api/error] Fake error - Sentry test from /api/error
2021-06-24T20:33:52.953Z	3751ccb9-311e-4e5d-87b1-6b1a1aa04ce9	ERROR	2021-06-24T20:33:35.287Z [modules/core/sentry/universal] [flushSafe] An exception was thrown while running Sentry.flush() false

import { logEvent } from '@/modules/core/amplitude/amplitudeServerClient';
import {
  AMPLITUDE_API_ENDPOINTS,
  AMPLITUDE_EVENTS,
} from '@/modules/core/amplitude/events';
import { createLogger } from '@/modules/core/logging/logger';
import { configureReq } from '@/modules/core/sentry/server';
import { flushSafe } from '@/modules/core/sentry/universal';
import * as Sentry from '@sentry/node';
import {
  NextApiRequest,
  NextApiResponse,
} from 'next';

const fileLabel = 'api/error';
const logger = createLogger({
  fileLabel,
});

/**
 * Error endpoint - Throws an error upon being called.
 *
 * Mock API endpoint whose sole purpose is to throw an error, nothing else.
 * Meant to be used to check whether monitoring (Sentry) works as expected.
 *
 * @param req
 * @param res
 * @method GET
 */
export const error = async (req: NextApiRequest, res: NextApiResponse): Promise<void> => {
  try {
    configureReq(req, { fileLabel });

    await logEvent(AMPLITUDE_EVENTS.API_INVOKED, null, {
      apiEndpoint: AMPLITUDE_API_ENDPOINTS.ERROR,
    });

    throw Error('Fake error - Sentry test from /api/error');
  } catch (e) {
    Sentry.captureException(e);
    logger.error(e.message);

    await flushSafe();

    res.json({
      error: true,
      message: process.env.NEXT_PUBLIC_APP_STAGE === 'production' ? undefined : e.message,
    });
  }
};

/**
 * Flushes Sentry queue in a safe way.
 *
 * It's necessary to flush all Sentry events on the server, because Vercel runs on AWS Lambda, see https://vercel.com/docs/platform/limits#streaming-responses
 * If you don't flush, then it's possible the Sentry events won't be sent.
 * This helper is meant to be used for backend-only usage. (not frontend)
 *
 * There is a potential bug in Sentry that throws an exception when flushing times out, causing API endpoints to fail.
 * @see https://github.com/getsentry/sentry/issues/26870
 */
export const flushSafe = async (): Promise<boolean> => {
  try {
    return await Sentry.flush(FLUSH_TIMEOUT);
  } catch (e) {
    logger.error(`[flushSafe] An exception was thrown while running Sentry.flush()`, e);
    return false;
  }
};

export default error;

[Vadorequest]

The reason behind this behavior is because Sentry.init() wasn't called and no SENTRY_DSN was provided.

When providing SENTRY_DSN, this error goes away.

The behaviour when SENTRY_DSN isn't defined is really confusing and misleading.

[lobsterkatie]

Hi, @Vadorequest.

Once 6.10.0 is released (hopefully tomorrow), can you please give this another try? Two separate problems were causing this, I believe - one related to the SDK not starting up, and one related to flush (which withSentry calls), and they have hopefully been resolved here and here.

I'm going to close this, but please reach out if you're still having trouble.

Thanks!