"Cannot set headers after they are sent to the client" (ERR_HTTP_HEADERS_SENT) with AmazonDaxClient

[rchl]

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

Version:

6.17.5

Description

This affects a complicated setup that I can't provide reproduction for easily.

The setup is:

• and express backend with express-session middleware running
• custom session store that retrieves and stores session in a DynamoDB database and uses AmazonDaxClient for DB operations

Steps are:

• navigate to express route that just returns some data res.json('OK')
• The express-middleware reads the session before handling the route and tries to save it on res.end() (which express-session wraps)
• When the saving of the session fails the dax client emits an error event:
  
• The emitted event seems to get handled by Sentry itself in the code linked below, resulting in the next express middleware running, even though the previous one has already responded to the request:
  

  sentry-javascript/packages/node/src/handlers.ts

  Lines 393 to 416 in a79c097

  	}
  	return function sentryRequestMiddleware(
  	req: http.IncomingMessage,
  	res: http.ServerResponse,
  	next: (error?: any) => void,
  	): void {
  	if (options && options.flushTimeout && options.flushTimeout > 0) {
  	// eslint-disable-next-line @typescript-eslint/unbound-method
  	const _end = res.end;
  	res.end = function (chunk?: any | (() => void), encoding?: string | (() => void), cb?: () => void): void {
  	void flush(options.flushTimeout)
  	.then(() => {
  	_end.call(this, chunk, encoding, cb);
  	})
  	.then(null, e => {
  	logger.error(e);
  	});
  	};
  	}
  	const local = domain.create();
  	local.add(req);
  	local.add(res);
  	local.on('error', next);

• The difference with and without Sentry is that this.domain is not defined in the code below when Sentry is not used
  

When the issue triggers then we are getting the ERR_HTTP_HEADERS_SENT error from Node because some later error middleware runs even though we've responded already.

[AbhiPrasad]

Thanks for the detailed issue. Could you provide your Sentry.init config. Are you using tracing?

I assume there's a conflict with domains here, but I'm not familiar enough with express middlewares to be certain. I'm putting this in our backlog to address, but PRs welcome for anyone who wants to help out!

[rchl]

The init options are not relevant because I have reproduced that even without initializing Sentry. It's just about the the Sentry requestHandler apparently.

Here is minimal reproduction that reproduces with minimal dummy express-session store:
https://github.com/rchl/sentry-bug-repro

[edennis]

I'm also getting the same error. I've used git-bisect to determine that the regression was introduced in 6.14.0 (6.13.3 works fine).

[souredoutlook]

@lobsterkatie Just confirming that the ongoing solution to this for affected users has been to downgrade to 6.13.3